{"gene":"PBANKA_1101300","run_date":"2026-09-07T10:55:50","timeline":{"discoveries":[{"year":2000,"finding":"SBP1 (PfSBP1) is an integral membrane protein of Maurer's clefts in P. falciparum-infected erythrocytes; its carboxy-terminal domain, exposed in the host cell cytoplasm, interacts with a 35 kDa erythrocyte skeletal protein, suggesting it participates in anchoring Maurer's clefts to the erythrocyte submembrane skeleton. Antibodies to both termini of PfSBP1 also labelled vesicular structures in P. berghei-infected erythrocytes, indicating conservation across malaria species.","method":"Immunoprecipitation with hyperimmune sera, biochemical characterization, antibody labelling of infected erythrocytes from multiple Plasmodium species","journal":"Molecular and biochemical parasitology","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — single Co-IP/pulldown identifying a 35 kDa partner without its identity; cross-species antibody labelling supports conservation; single lab","pmids":["11087921"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""},{"species":"Plasmodium berghei","strain":""},{"species":"Plasmodium chabaudi","strain":""}]},{"year":2006,"finding":"Targeted gene disruption of SBP1 in P. falciparum prevented PfEMP1 surface expression on infected red blood cells and abolished cytoadhesion; PfEMP1 was retained in Maurer's clefts and Maurer's clefts were displaced from the erythrocyte periphery. Complementation with sbp1 restored PfEMP1 surface expression and adhesion, demonstrating SBP1 is essential for PfEMP1 translocation to the infected erythrocyte surface.","method":"Targeted gene disruption (knockout), genetic complementation, immunofluorescence, adhesion assays","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — clean KO with defined cellular phenotype, genetic complementation confirming specificity, replicated by multiple orthogonal assays","pmids":["16520384"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2006,"finding":"PfSBP1 functions at the parasitophorous vacuole membrane (PVM) to load PfEMP1 into Maurer's clefts during formation of these structures; loss of PfSBP1 abolished PfEMP1 surface display and the major antibody reactivity of multigravid women directed at PfEMP1.","method":"Genetic disruption of SBP1, immunofluorescence microscopy, antibody reactivity assays with immune sera","journal":"Blood","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic loss-of-function with defined pathway placement at PVM, consistent with PMID 16520384, two independent labs","pmids":["17023587"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2006,"finding":"Parasite protein phosphatase 1 (PP1), localized to Maurer's clefts, modulates the phosphorylation status of the amino-terminal domain of PfSBP1 within the lumen of Maurer's clefts, as shown by co-immunoprecipitation and phosphatase inhibition. Hyperphosphorylation of PfSBP1 induced by the PP1 inhibitor calyculin A in late schizonts prevented merozoite release, linking SBP1 phosphorylation state to red blood cell membrane stability.","method":"Co-immunoprecipitation, pharmacological inhibition with calyculin A, observation of merozoite release block","journal":"Cellular microbiology","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — single lab Co-IP plus pharmacological inhibitor phenotype; phosphorylation site mapping not performed at atomic resolution","pmids":["16548885"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2005,"finding":"The carboxy-terminal cytoplasmic domain of PfSBP1 on Maurer's clefts interacts with the host erythrocyte cytosolic protein LANCL1; LANCL1 is specifically recruited to the surface of Maurer's clefts in mature P. falciparum blood stages, implicating this interaction in preventing premature rupture of the red blood cell membrane.","method":"Co-immunoprecipitation, mass spectrometry identification of LANCL1, immunofluorescence localization in infected erythrocytes","journal":"Molecular and biochemical parasitology","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — Co-IP with MS identification of partner and localization; single lab, functional inference not directly tested","pmids":["15811525"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2008,"finding":"The transmembrane domain of PfSBP1 functions as an internal signal sequence for entry into the parasite's secretory pathway and transport to the parasite plasma membrane; trafficking beyond the parasite plasma membrane additionally requires N-terminal domains with high negative net charge, which influence protein solubility, membrane orientation, and subcellular localization. PfSBP1 lacks the PEXEL/VTS motif and is not N-terminally processed.","method":"Domain-deletion mutagenesis, chimeric reporter constructs, biochemical fractionation, immunofluorescence","journal":"Traffic (Copenhagen, Denmark)","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — mutagenesis with functional readout in multiple constructs, single lab","pmids":["19054387"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2008,"finding":"The N-terminal region and transmembrane domain of PfSBP1 can functionally replace the corresponding regions in the PEXEL-negative exported protein REX2 to promote export, demonstrating these sequence features are shared among PEXEL-negative exported proteins and are functionally interchangeable.","method":"Chimeric protein domain-swap constructs expressed in P. falciparum, fluorescence microscopy","journal":"Molecular microbiology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — functional domain-swap experiment with defined export readout; single lab","pmids":["19170882"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2008,"finding":"PfSBP1 physically interacts with the molecular chaperone PfBiP during early export steps, as revealed by the conditional aggregation domain (CAD) export system; this interaction occurs prior to arrival at Maurer's clefts.","method":"Conditional protein export system (CAD domain fused to full-length PfSBP1), co-immunoprecipitation of intermediate complexes","journal":"Cellular microbiology","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — single Co-IP using engineered conditional system; single lab but novel method","pmids":["18691247"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2013,"finding":"Plasmepsin V does not cleave the N-terminal sequence of SBP1 (a PEXEL-negative exported protein), establishing that SBP1 export is independent of Plasmepsin V processing.","method":"In vitro Plasmepsin V cleavage assay, N-terminal sequencing","journal":"Traffic (Copenhagen, Denmark)","confidence":"Medium","confidence_rationale":"Tier 1 / Weak — in vitro enzymatic assay; negative result mechanistically informative; single lab","pmids":["23387285"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2015,"finding":"A defined region of PfSBP1 binds specifically to sub-domains of two major erythrocyte membrane skeleton components, protein 4.1R and spectrin; these interactions anchor Maurer's clefts to the red blood cell membrane skeleton but are necessary yet not sufficient for PfEMP1 translocation to the RBC surface. The N-terminal domain of SBP1 within the Maurer's cleft lumen plays an essential but unidentified additional role.","method":"GST pulldown, domain-deletion mapping, binding assays with recombinant erythrocyte skeleton proteins, co-localization","journal":"Biochimica et biophysica acta","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — pulldown with domain mapping; binding partners identified; functional sufficiency tested; single lab","pmids":["25883090"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2015,"finding":"Three resident Maurer's cleft membrane proteins including PfSBP1 are exported as soluble forms in the red cell cytoplasm and associate with the parasite group II chaperonin PfTRiC; the domain of interaction with PfTRiC was mapped within the amino-terminal domain of PfSBP1.","method":"Co-immunoprecipitation, domain mapping, subcellular fractionation","journal":"Traffic (Copenhagen, Denmark)","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — Co-IP with domain mapping; single lab; proposed general role for PfTRiC supported by data on multiple cleft proteins","pmids":["25615740"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2016,"finding":"P. berghei orthologues of SBP1 and MAHRP1 were identified; red blood cells infected with P. berghei parasites lacking SBP1 fail to bind the endothelial receptor CD36 and show reduced sequestration and virulence in mice. Complementation of P. berghei SBP1 knockout parasites with P. falciparum SBP1 restored sequestration and virulence, demonstrating evolutionary conservation of SBP1 function across divergent malaria parasites.","method":"Gene knockout in P. berghei, cross-species complementation with P. falciparum SBP1, in vivo sequestration assays (bioluminescence imaging), CD36 binding assays, virulence assessment in mice","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic KO with defined cellular phenotype, cross-species functional complementation, multiple orthogonal in vivo readouts","pmids":["27225796"],"is_preprint":false,"attribution":[{"species":"Plasmodium berghei","strain":""},{"species":"Plasmodium falciparum","strain":""}]},{"year":2016,"finding":"Genetic deletion of SBP1 in P. falciparum dramatically reduced antibody recognition of infected erythrocytes and abolished the ability of human antibodies to promote opsonic phagocytosis, demonstrating that SBP1 is part of a critical trafficking pathway for the dominant surface antigens (primarily PfEMP1) targeted by acquired human immunity.","method":"Genetic deletion of SBP1, flow cytometry-based antibody binding assays, opsonic phagocytosis assays, multiple parasite isolates and immune sera from different populations","journal":"Cellular and molecular life sciences : CMLS","confidence":"High","confidence_rationale":"Tier 2 / Strong — clean KO with multiple orthogonal functional assays; replicated across multiple parasite isolates and population cohorts","pmids":["27193441"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2016,"finding":"P. knowlesi SBP1 (PkSBP1), when expressed as an epitope-tagged recombinant protein, localizes to membranous structures (Sinton and Mulligan stipplings) analogous to Maurer's clefts in monkey and human erythrocytes; when expressed in P. falciparum-infected erythrocytes, PkSBP1 co-localizes with PfSBP1 at Maurer's clefts, demonstrating conservation of the trafficking pathway.","method":"Transgenic parasite expression of epitope-tagged PkSBP1, immunofluorescence assay, immunoelectron microscopy, co-localization with PfSBP1","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct localization by IFA and immuno-EM with functional implication of conserved trafficking; single lab","pmids":["27732628"],"is_preprint":false,"attribution":[{"species":"Plasmodium knowlesi","strain":""}]},{"year":2017,"finding":"PHISTc protein PFD1140w interacts with both PfSBP1 and PfEMP1 simultaneously in vitro, forming a tripartite complex; a direct binding interaction between recombinant PHIST proteins and PfSBP1 was detected, identifying PfSBP1 as a novel binding partner of PHISTc family members.","method":"In vitro pulldown/binding assays with recombinant proteins, co-immunoprecipitation, co-localization by immunofluorescence","journal":"The FEBS journal","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — in vitro binding with recombinant proteins and Co-IP; tripartite complex formation demonstrated; single lab","pmids":["29155505"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2019,"finding":"Using time-resolved proximity biotinylation (SBP1 fused to TurboID), two groups of SBP1 interactors were identified: early (pre-export) and late (post-export). Two membrane-associated proteins were identified as pre-export interactors, one with a predicted translocon domain, suggesting they facilitate extraction of SBP1 from the parasite plasma membrane for export.","method":"TurboID proximity biotinylation fused to SBP1, label-free quantitative proteomics, conditional mutants of candidate proteins, fluorescence localization","journal":"Journal of cell science","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — proximity biotinylation proteomics with temporal resolution; candidate validation by conditional mutants; single lab","pmids":["37772444"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2019,"finding":"A comprehensive SBP1 interactome was determined in P. falciparum-infected erythrocytes using unbiased proteomic approaches; SBP1 interactomes revealed numerous exported proteins and potential interactors associated with SBP1 intracellular trafficking, including host-parasite protein interactions. The exported protein MAL8P1.4 was linked to P. falciparum virulence via this interaction network.","method":"Proteomic interaction mapping (co-immunoprecipitation/AP-MS), label-free quantitative mass spectrometry","journal":"iScience","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — comprehensive AP-MS interactome; single lab; individual interactions not validated by orthogonal methods","pmids":["31476617"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2019,"finding":"SBP1 accumulates in electron-dense material (EDM) in the parasite cytoplasm during the early trophozoite (ring form) stage and is subsequently found in the parasitophorous vacuolar (PV) space before translocation to Maurer's clefts, defining an intermediate trafficking step for SBP1 export.","method":"Immunoelectron microscopy with anti-SBP1 antibodies raised against recombinant PfSBP1","journal":"Parasitology international","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct ultrastructural localization by immunoelectron microscopy; single lab; defines trafficking intermediate","pmids":["31669509"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2023,"finding":"SBP1 and MAHRP2 assume a lumenal topology within the parasite secretory pathway (ER lumen), forming ER-lumenal intermediates during export; addition of a C-terminal KDEL ER-retention sequence enhanced retention of SBP1 in the parasite ER, indicating that a sub-population of SBP1 adopts an ER-lumenal state that is a productive intermediate in the export process. SBP1 is targeted by an internal hydrophobic sequence that, unlike a transmembrane segment, does not span the ER membrane.","method":"Chimeric reporter constructs with ER-retention sequences, intact-cell topology assays, fluorescence microscopy, mass spectrometry","journal":"PLoS pathogens","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple chimeric constructs with functional retention assays and topology determination; novel mechanistic insight; single lab","pmids":["37000891"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2024,"finding":"SBP1 is expressed in gametocyte-infected erythrocytes and localizes to dot-like Maurer's cleft structures in their cytoplasm; co-immunoprecipitation followed by mass spectrometry identified PfHSP70-1 and PfHSP70-x as SBP1-interacting molecular chaperones in gametocyte-infected erythrocytes, with some HSP70 co-localizing in a dot-like cytoplasmic pattern in immature gametocytes.","method":"Co-immunoprecipitation, mass spectrometry, immunofluorescence localization in gametocyte-infected erythrocytes","journal":"Parasitology international","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — Co-IP/MS identification of chaperone partners with supporting localization; single lab; gametocyte stage not previously characterized for SBP1","pmids":["38331312"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2018,"finding":"Direct in vitro interaction was demonstrated between purified PfSBP1 and recombinant PfJ23 (a PEXEL-positive hyp16 family member); PfJ23, PfSBP1 and PfEMP1 can form a tripartite complex in vitro, and PfJ23 partially co-localizes with PfSBP1 in parasite-infected erythrocytes.","method":"In vitro pulldown with recombinant proteins, co-immunoprecipitation with native proteins, immunofluorescence co-localization","journal":"Pathogens and disease","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single lab, single Co-IP/pulldown, functional implication proposed but not directly tested","pmids":["30576479"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2019,"finding":"The cytoplasmic domain of CBP2 (cCBP2) interacts in vitro with PfSBP1; this interaction is influenced by ATP binding to cCBP2, which induces structural changes in the protein.","method":"In vitro binding assay with recombinant proteins, biophysical characterization","journal":"International journal of biological macromolecules","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single in vitro binding assay; single lab; no cellular validation of interaction","pmids":["31356937"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2021,"finding":"SBP1 KO P. berghei parasites (lacking sequestration ability) induced similar early lung pathology as wild-type parasites in experimental MA-ARDS, but lung pathology resolved in >60% of SBP1 KO-infected mice, associated with decreased inflammatory cytokine expression and lower cytotoxic CD8+ T cell markers; this establishes that SBP1-mediated sequestration inhibits spontaneous disease resolution rather than being required for initial pathology.","method":"SBP1 KO P. berghei in vivo mouse model, bioluminescence imaging, RT-qPCR (parasite load and cytokines), flow cytometry for CD8+ T cells, histopathology","journal":"PLoS pathogens","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — clean genetic KO with multiple in vivo readouts; mechanistic pathway placement via epistasis; single lab","pmids":["34843584"],"is_preprint":false,"attribution":[{"species":"Plasmodium berghei","strain":"NK65"}]}],"current_model":"SBP1 (PBANKA_1101300/PfSBP1) is an integral membrane protein of Maurer's clefts that traffics through an ER-lumenal intermediate and the parasitophorous vacuole membrane to reach its destination; its transmembrane domain serves as an internal signal sequence for secretory pathway entry, while N-terminal negatively charged domains govern membrane orientation and export competence; at the Maurer's cleft, SBP1 is essential for translocation of PfEMP1 to the infected erythrocyte surface (likely by anchoring Maurer's clefts to the host membrane skeleton via interactions with protein 4.1R and spectrin), interacts with host LANCL1, parasite chaperones PfTRiC, PfBiP, PfHSP70-1, and PfHSP70-x, and PHISTc/PfJ23 family exported proteins; its phosphorylation state is modulated by a cleft-resident PP1 phosphatase; and its function is evolutionarily conserved in P. berghei, where SBP1 mediates parasite sequestration, virulence, and inhibition of spontaneous resolution of malaria-associated acute respiratory distress syndrome."},"narrative":{"mechanistic_narrative":"SBP1 (PBANKA_1101300/PfSBP1) is an integral membrane protein resident at the Maurer's clefts of malaria parasite-infected erythrocytes that is essential for the export machinery delivering parasite virulence antigens to the host red-cell surface [PMID:11087921, PMID:16520384]. Genetic disruption of SBP1 in P. falciparum retains PfEMP1 within Maurer's clefts, abolishes its surface display and cytoadhesion, and is rescued by complementation, establishing SBP1 as an indispensable component of the PfEMP1 translocation pathway acting during cleft formation at the parasitophorous vacuole membrane [PMID:16520384, PMID:17023587]; loss of SBP1 correspondingly collapses antibody recognition and opsonic phagocytosis of infected cells, placing it upstream of the dominant surface antigens targeted by acquired immunity [PMID:27193441]. SBP1 anchors Maurer's clefts to the erythrocyte membrane skeleton through its C-terminal cytoplasmic domain, which binds a 35 kDa skeletal protein and, more specifically, sub-domains of protein 4.1R and spectrin, an interaction necessary but not sufficient for PfEMP1 surface delivery, while an essential lumenal role for its N-terminal domain remains uncharacterized [PMID:11087921, PMID:25883090]. SBP1 reaches the clefts via a distinctive PEXEL/VTS-independent, Plasmepsin V-independent route: its internal hydrophobic segment serves as an internal signal for secretory-pathway entry and transits an ER-lumenal intermediate, with N-terminal negatively charged domains governing membrane orientation and export competence [PMID:19054387, PMID:23387285, PMID:37000891]. This trafficking is chaperone-dependent, engaging PfBiP and the group II chaperonin PfTRiC during early soluble export intermediates and passing through electron-dense cytoplasmic material and the parasitophorous vacuolar space before cleft delivery [PMID:18691247, PMID:25615740, PMID:31669509]. SBP1 function is deeply conserved: cross-species complementation with P. falciparum SBP1 restores CD36 binding, sequestration and virulence in P. berghei SBP1 knockouts, and in a P. berghei model SBP1-mediated sequestration inhibits spontaneous resolution of malaria-associated acute respiratory distress syndrome rather than driving initial pathology [PMID:27225796, PMID:34843584].","teleology":[{"year":2000,"claim":"Establishing that SBP1 is a Maurer's cleft integral membrane protein whose cytoplasmic C-terminus engages the host skeleton framed it as a candidate linker between parasite-induced structures and the erythrocyte membrane.","evidence":"Immunoprecipitation and biochemical characterization plus cross-species antibody labelling of infected erythrocytes","pmids":["11087921"],"confidence":"Medium","gaps":["Identity of the 35 kDa erythrocyte partner not determined","Functional consequence of the anchoring interaction not tested"],"attribution":[{"species":"Plasmodium falciparum","strain":""},{"species":"Plasmodium berghei","strain":""},{"species":"Plasmodium chabaudi","strain":""}]},{"year":2005,"claim":"Identifying host LANCL1 as a partner of the SBP1 C-terminal cytoplasmic domain extended the anchoring model to specific host cytosolic recruitment at the cleft surface.","evidence":"Co-immunoprecipitation with mass spectrometry identification and immunofluorescence in infected erythrocytes","pmids":["15811525"],"confidence":"Medium","gaps":["Proposed role in preventing premature RBC rupture not directly tested","Single lab, no functional loss-of-function of the interaction"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2006,"claim":"Gene disruption resolved whether SBP1 is merely a structural resident or functionally required, showing it is essential for translocating PfEMP1 to the infected-cell surface and for cytoadhesion, and placing its action at the PVM during cleft formation.","evidence":"Targeted knockout with genetic complementation, immunofluorescence, and adhesion/antibody-reactivity assays in P. falciparum","pmids":["16520384","17023587"],"confidence":"High","gaps":["Molecular mechanism of PfEMP1 hand-off not defined","Whether SBP1 acts directly on PfEMP1 or indirectly via cleft architecture unresolved"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2006,"claim":"Linking a cleft-resident PP1 to the phosphorylation state of the SBP1 N-terminal domain connected reversible SBP1 modification to red-cell membrane stability and merozoite release.","evidence":"Co-immunoprecipitation and calyculin A inhibition with observation of blocked merozoite release","pmids":["16548885"],"confidence":"Medium","gaps":["Phosphorylation sites not mapped at residue resolution","Direct causal link between SBP1 phosphorylation and release not isolated from other PP1 substrates"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2008,"claim":"Dissecting the export signals showed SBP1 uses a PEXEL-independent route in which its transmembrane segment acts as an internal signal and negatively charged N-terminal domains license export, defining the sequence logic of a PEXEL-negative exported protein.","evidence":"Domain-deletion and chimeric reporter mutagenesis with fractionation and microscopy; domain swaps onto REX2; CAD conditional export system identifying PfBiP interaction","pmids":["19054387","19170882","18691247"],"confidence":"Medium","gaps":["Machinery recognizing the internal signal not identified","Order of chaperone engagement not fully resolved"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2013,"claim":"An in vitro cleavage assay confirmed SBP1 export is independent of Plasmepsin V processing, cementing its classification within the PEXEL-negative export pathway.","evidence":"In vitro Plasmepsin V cleavage assay with N-terminal sequencing","pmids":["23387285"],"confidence":"Medium","gaps":["Negative in vitro result; alternative processing events not excluded"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2015,"claim":"Mapping SBP1 binding to protein 4.1R/spectrin sub-domains and to the chaperonin PfTRiC clarified both the host-skeleton anchoring interface and a soluble chaperone-assisted export intermediate, while revealing that skeleton binding is necessary but not sufficient for PfEMP1 surface delivery.","evidence":"GST pulldowns and domain mapping with recombinant skeleton proteins; co-IP and fractionation identifying PfTRiC interaction mapped to the N-terminal domain","pmids":["25883090","25615740"],"confidence":"Medium","gaps":["The additional essential lumenal N-terminal function remains unidentified","Interactions not validated by orthogonal in-cell methods"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2016,"claim":"Cross-species knockout and complementation established that SBP1 function is evolutionarily conserved, mediating CD36 binding, sequestration and virulence in P. berghei, and that its trafficking pathway underlies immune recognition of infected cells.","evidence":"P. berghei knockout with P. falciparum complementation and in vivo sequestration/virulence readouts; P. falciparum deletion coupled to antibody-binding and opsonic phagocytosis assays; PkSBP1 localization by IFA and immuno-EM","pmids":["27225796","27193441","27732628"],"confidence":"High","gaps":["Conserved molecular partners across species not fully mapped","How SBP1 loss translates to loss of specific surface antigens beyond PfEMP1 not delineated"],"attribution":[{"species":"Plasmodium berghei","strain":""},{"species":"Plasmodium falciparum","strain":""},{"species":"Plasmodium knowlesi","strain":""}]},{"year":2017,"claim":"Demonstrating that SBP1 can bind PHISTc protein PFD1140w and PfEMP1 simultaneously identified it as a scaffolding node in a tripartite complex, suggesting how it organizes PfEMP1 within clefts.","evidence":"In vitro binding with recombinant proteins, co-IP, and co-localization","pmids":["29155505"],"confidence":"Medium","gaps":["Tripartite complex shown in vitro; physiological stoichiometry and in-cell assembly not established"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2019,"claim":"Temporal proximity biotinylation, AP-MS interactome mapping, and ultrastructural localization resolved SBP1's export itinerary and its distinct pre- and post-export interactor sets, including a candidate translocon-domain protein and an intermediate through electron-dense material and the PV space.","evidence":"TurboID proximity proteomics with conditional mutants; AP-MS interactome; immunoelectron microscopy","pmids":["37772444","31476617","31669509"],"confidence":"Medium","gaps":["Direct extraction/translocon mechanism at the parasite plasma membrane not proven","Most interactome hits not individually validated"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2021,"claim":"An epistasis experiment in an MA-ARDS model showed SBP1-mediated sequestration inhibits spontaneous disease resolution rather than being required for initial lung pathology, refining SBP1's role in disease progression.","evidence":"SBP1 knockout P. berghei NK65 mouse model with bioluminescence imaging, cytokine RT-qPCR, CD8+ T-cell flow cytometry, and histopathology","pmids":["34843584"],"confidence":"Medium","gaps":["Mechanism linking sequestration to sustained inflammation not defined","Single lab, single strain"],"attribution":[{"species":"Plasmodium berghei","strain":"NK65"}]},{"year":2023,"claim":"Topology analysis revealed a productive ER-lumenal intermediate for SBP1 export, showing its internal hydrophobic sequence does not span the ER membrane and refining the mechanism of secretory-pathway entry.","evidence":"Chimeric reporters with KDEL retention, intact-cell topology assays, microscopy and mass spectrometry","pmids":["37000891"],"confidence":"Medium","gaps":["How the lumenal intermediate is converted to a membrane-integral cleft form not resolved","Single lab"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2024,"claim":"Extending SBP1 study to gametocytes showed it localizes to cleft-like structures there and associates with PfHSP70-1 and PfHSP70-x, indicating chaperone-assisted handling across life-cycle stages.","evidence":"Co-immunoprecipitation with mass spectrometry and immunofluorescence in gametocyte-infected erythrocytes","pmids":["38331312"],"confidence":"Medium","gaps":["Functional role of SBP1 in gametocytes not tested","Chaperone interactions not functionally dissected"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":null,"claim":"The essential lumenal N-terminal function of SBP1, the direct molecular mechanism by which it hands PfEMP1 to the surface, and the identity of the machinery recognizing its internal export signal remain unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No structure of SBP1 or its complexes","Mechanism of PfEMP1 translocation downstream of skeleton anchoring unknown","Translocon that extracts SBP1 for export not definitively identified"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]}],"mechanism_profile":{"molecular_activity":[],"localization":[],"pathway":[],"complexes":["SBP1–PHISTc(PFD1140w)–PfEMP1 tripartite complex [#14]","SBP1–PfJ23–PfEMP1 tripartite complex [#20]"],"partners":["ERYTHROCYTE PROTEIN 4.1R [#9]","ERYTHROCYTE SPECTRIN [#9]","35 KDA ERYTHROCYTE SKELETAL PROTEIN [#0]","HOST LANCL1 [#4]","PFBIP [#7]","PFTRIC (GROUP II CHAPERONIN) [#10]","PFHSP70-1 [#19]","PFHSP70-X [#19]","PHISTC PFD1140W [#14]","PFJ23 [#20]","CBP2 CYTOPLASMIC DOMAIN [#21]","PFEMP1 (FUNCTIONAL/COMPLEX PARTNER) [#1, #14, #20]"],"other_free_text":["SBP1 is a PEXEL/VTS-negative exported protein that is not N-terminally processed and whose export is independent of Plasmepsin V [#5, #8].","Its transmembrane/internal hydrophobic segment acts as an internal signal for secretory-pathway entry; N-terminal negatively charged domains govern membrane orientation and export competence [#5, #18].","SBP1 phosphorylation state is modulated by a Maurer's-cleft-resident PP1; hyperphosphorylation blocks merozoite release [#3].","SBP1 function is evolutionarily conserved: P. falciparum SBP1 complements P. berghei SBP1 knockouts for sequestration and virulence [#11].","In P. berghei, SBP1-mediated sequestration inhibits spontaneous resolution of malaria-associated acute respiratory distress syndrome rather than driving initial pathology [#22]."]}},"prefetch_data":{},"corpus_meta":[{"pmid":"11087921","id":"PMC_11087921","title":"Pfsbp1, a Maurer's cleft Plasmodium falciparum protein, is associated with the erythrocyte skeleton.","date":"2000","source":"Molecular and biochemical parasitology","url":"https://pubmed.ncbi.nlm.nih.gov/11087921","citation_count":195,"is_preprint":false,"source_species":["Pb"],"role":"primary","match_terms":["skeleton-binding protein 1","PfSBP1"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"16520384","id":"PMC_16520384","title":"A Maurer's cleft-associated protein is essential for expression of the major malaria virulence antigen on the surface of infected red blood cells.","date":"2006","source":"The Journal of cell biology","url":"https://pubmed.ncbi.nlm.nih.gov/16520384","citation_count":152,"is_preprint":false,"source_species":["Pb"],"role":"primary","match_terms":["SBP1","skeleton-binding protein 1"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"17023587","id":"PMC_17023587","title":"Skeleton-binding protein 1 functions at the parasitophorous vacuole membrane to traffic PfEMP1 to the Plasmodium falciparum-infected erythrocyte surface.","date":"2006","source":"Blood","url":"https://pubmed.ncbi.nlm.nih.gov/17023587","citation_count":137,"is_preprint":false,"source_species":["Pb"],"role":"primary","match_terms":["skeleton-binding protein 1","PfSBP1"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"23387285","id":"PMC_23387285","title":"Role of plasmepsin V in export of diverse protein families from the Plasmodium falciparum exportome.","date":"2013","source":"Traffic (Copenhagen, Denmark)","url":"https://pubmed.ncbi.nlm.nih.gov/23387285","citation_count":108,"is_preprint":false,"source_species":["Pb"],"role":"primary","match_terms":["SBP1"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"19170882","id":"PMC_19170882","title":"Sequence requirements for the export of the Plasmodium falciparum Maurer's clefts protein REX2.","date":"2008","source":"Molecular microbiology","url":"https://pubmed.ncbi.nlm.nih.gov/19170882","citation_count":71,"is_preprint":false,"source_species":["Pb"],"role":"primary","match_terms":["SBP1","skeleton-binding protein 1"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"27225796","id":"PMC_27225796","title":"The machinery underlying malaria parasite virulence is conserved between rodent and human malaria parasites.","date":"2016","source":"Nature communications","url":"https://pubmed.ncbi.nlm.nih.gov/27225796","citation_count":60,"is_preprint":false,"source_species":["Pb"],"role":"primary","match_terms":["SBP1"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"19054387","id":"PMC_19054387","title":"Export of PfSBP1 to the Plasmodium falciparum Maurer's clefts.","date":"2008","source":"Traffic (Copenhagen, Denmark)","url":"https://pubmed.ncbi.nlm.nih.gov/19054387","citation_count":59,"is_preprint":false,"source_species":["Pb"],"role":"primary","match_terms":["skeleton-binding protein 1","PfSBP1"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"16548885","id":"PMC_16548885","title":"Protein phosphatase 1, a Plasmodium falciparum essential enzyme, is exported to the host cell and implicated in the release of infectious merozoites.","date":"2006","source":"Cellular microbiology","url":"https://pubmed.ncbi.nlm.nih.gov/16548885","citation_count":40,"is_preprint":false,"source_species":["Pb"],"role":"primary","match_terms":["skeleton-binding protein 1","PfSBP1"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"15811525","id":"PMC_15811525","title":"LANCL1, an erythrocyte protein recruited to the Maurer's clefts during Plasmodium falciparum development.","date":"2005","source":"Molecular and biochemical parasitology","url":"https://pubmed.ncbi.nlm.nih.gov/15811525","citation_count":34,"is_preprint":false,"source_species":["Pb"],"role":"primary","match_terms":["PfSBP1"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"25883090","id":"PMC_25883090","title":"Interactions between Plasmodium falciparum skeleton-binding protein 1 and the membrane skeleton of malaria-infected red blood cells.","date":"2015","source":"Biochimica et biophysica acta","url":"https://pubmed.ncbi.nlm.nih.gov/25883090","citation_count":26,"is_preprint":false,"source_species":["Pb"],"role":"primary","match_terms":["SBP1","skeleton-binding protein 1"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"18691247","id":"PMC_18691247","title":"A conditional export system provides new insights into protein export in Plasmodium falciparum-infected erythrocytes.","date":"2008","source":"Cellular microbiology","url":"https://pubmed.ncbi.nlm.nih.gov/18691247","citation_count":26,"is_preprint":false,"source_species":["Pb"],"role":"primary","match_terms":["PfSBP1"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"28719294","id":"PMC_28719294","title":"Molecular Markers for Sensitive Detection of Plasmodium falciparum Asexual Stage Parasites and their Application in a Malaria Clinical Trial.","date":"2017","source":"The American journal of tropical medicine and hygiene","url":"https://pubmed.ncbi.nlm.nih.gov/28719294","citation_count":24,"is_preprint":false,"source_species":["Pb"],"role":"primary","match_terms":["SBP1","skeleton-binding protein 1"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"22043276","id":"PMC_22043276","title":"Amplification of P. falciparum Cytoadherence through induction of a pro-adhesive state in host endothelium.","date":"2011","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/22043276","citation_count":22,"is_preprint":false,"source_species":["Pb"],"role":"primary","match_terms":["PfSBP1"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"27193441","id":"PMC_27193441","title":"A single point in protein trafficking by Plasmodium falciparum determines the expression of major antigens on the surface of infected erythrocytes targeted by human antibodies.","date":"2016","source":"Cellular and molecular life sciences : CMLS","url":"https://pubmed.ncbi.nlm.nih.gov/27193441","citation_count":20,"is_preprint":false,"source_species":["Pb"],"role":"primary","match_terms":["SBP1","skeleton-binding protein 1"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"27732628","id":"PMC_27732628","title":"Plasmodium knowlesi Skeleton-Binding Protein 1 Localizes to the 'Sinton and Mulligan' Stipplings in the Cytoplasm of Monkey and Human Erythrocytes.","date":"2016","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/27732628","citation_count":16,"is_preprint":false,"source_species":["Pb"],"role":"primary","match_terms":["SBP1","skeleton-binding protein 1","PfSBP1","PkSBP1"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"29155505","id":"PMC_29155505","title":"PHISTc protein family members localize to different subcellular organelles and bind Plasmodium falciparum major virulence factor PfEMP-1.","date":"2017","source":"The FEBS journal","url":"https://pubmed.ncbi.nlm.nih.gov/29155505","citation_count":15,"is_preprint":false,"source_species":["Pb"],"role":"primary","match_terms":["skeleton-binding protein 1","PfSBP1"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"20419102","id":"PMC_20419102","title":"Functional evaluation of Plasmodium export signals in Plasmodium berghei suggests multiple modes of protein export.","date":"2010","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/20419102","citation_count":15,"is_preprint":false,"source_species":["Pb"],"role":"primary","match_terms":["skeleton-binding protein 1"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"25615740","id":"PMC_25615740","title":"New Export Pathway in Plasmodium falciparum-Infected Erythrocytes: Role of the Parasite Group II Chaperonin, PfTRiC.","date":"2015","source":"Traffic (Copenhagen, Denmark)","url":"https://pubmed.ncbi.nlm.nih.gov/25615740","citation_count":15,"is_preprint":false,"source_species":["Pb"],"role":"primary","match_terms":["PfSBP1"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"30608048","id":"PMC_30608048","title":"Plasmodium falciparum Gametocyte Enrichment in Peripheral Blood Samples by Magnetic Fractionation: Gametocyte Yields and Possibilities to Reuse Columns.","date":"2019","source":"The American journal of tropical medicine and hygiene","url":"https://pubmed.ncbi.nlm.nih.gov/30608048","citation_count":13,"is_preprint":false,"source_species":["Pb"],"role":"primary","match_terms":["SBP1"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"31476617","id":"PMC_31476617","title":"A High-Resolution Map of SBP1 Interactomes in Plasmodium falciparum-infected Erythrocytes.","date":"2019","source":"iScience","url":"https://pubmed.ncbi.nlm.nih.gov/31476617","citation_count":11,"is_preprint":false,"source_species":["Pb"],"role":"primary","match_terms":["SBP1","skeleton-binding protein 1"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"37772444","id":"PMC_37772444","title":"Time-resolved proximity biotinylation implicates a porin protein in export of transmembrane malaria parasite effectors.","date":"2023","source":"Journal of cell science","url":"https://pubmed.ncbi.nlm.nih.gov/37772444","citation_count":11,"is_preprint":false,"source_species":["Pb"],"role":"primary","match_terms":["SBP1","skeleton-binding protein 1"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"36004329","id":"PMC_36004329","title":"Experimental malaria-associated acute kidney injury is independent of parasite sequestration and resolves upon antimalarial treatment.","date":"2022","source":"Frontiers in cellular and infection microbiology","url":"https://pubmed.ncbi.nlm.nih.gov/36004329","citation_count":11,"is_preprint":false,"source_species":["Pb"],"role":"primary","match_terms":["SBP1","skeleton-binding protein 1"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"34843584","id":"PMC_34843584","title":"Skeleton binding protein-1-mediated parasite sequestration inhibits spontaneous resolution of malaria-associated acute respiratory distress syndrome.","date":"2021","source":"PLoS pathogens","url":"https://pubmed.ncbi.nlm.nih.gov/34843584","citation_count":11,"is_preprint":false,"source_species":["Pb"],"role":"primary","match_terms":["SBP1","skeleton-binding protein 1"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"29307564","id":"PMC_29307564","title":"Comparative genomics and proteomic analyses between lethal and nonlethal strains of Plasmodium berghei.","date":"2018","source":"Experimental parasitology","url":"https://pubmed.ncbi.nlm.nih.gov/29307564","citation_count":8,"is_preprint":false,"source_species":["Pb"],"role":"primary","match_terms":["SBP1","skeleton-binding protein 1"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"31669509","id":"PMC_31669509","title":"Skeleton binding protein 1 (SBP1) of Plasmodium falciparum accumulates in electron-dense material before passing through the parasitophorous vacuole membrane.","date":"2019","source":"Parasitology international","url":"https://pubmed.ncbi.nlm.nih.gov/31669509","citation_count":7,"is_preprint":false,"source_species":["Pb"],"role":"primary","match_terms":["SBP1","skeleton-binding protein 1"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"38714692","id":"PMC_38714692","title":"Persistent and multiclonal malaria parasite dynamics despite extended artemether-lumefantrine treatment in children.","date":"2024","source":"Nature communications","url":"https://pubmed.ncbi.nlm.nih.gov/38714692","citation_count":7,"is_preprint":false,"source_species":["Pb"],"role":"primary","match_terms":["SBP1"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"16843728","id":"PMC_16843728","title":"Deciphering the export pathway of malaria surface proteins.","date":"2006","source":"Trends in parasitology","url":"https://pubmed.ncbi.nlm.nih.gov/16843728","citation_count":7,"is_preprint":false,"source_species":["Pb"],"role":"primary","match_terms":["SBP1"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"33422068","id":"PMC_33422068","title":"Persistence of mRNA indicative of Plasmodium falciparum ring-stage parasites 42 days after artemisinin and non-artemisinin combination therapy in naturally infected Malians.","date":"2021","source":"Malaria journal","url":"https://pubmed.ncbi.nlm.nih.gov/33422068","citation_count":5,"is_preprint":false,"source_species":["Pb"],"role":"primary","match_terms":["SBP1"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"39927767","id":"PMC_39927767","title":"Isolation and characterization of Plasmodium falciparum blood-stage persisters by improved selection protocols using dihydroartemisinin alone.","date":"2025","source":"Antimicrobial agents and chemotherapy","url":"https://pubmed.ncbi.nlm.nih.gov/39927767","citation_count":5,"is_preprint":false,"source_species":["Pb"],"role":"primary","match_terms":["SBP1","skeleton-binding protein 1"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"37000891","id":"PMC_37000891","title":"Formation of ER-lumenal intermediates during export of Plasmodium proteins containing transmembrane-like hydrophobic sequences.","date":"2023","source":"PLoS pathogens","url":"https://pubmed.ncbi.nlm.nih.gov/37000891","citation_count":4,"is_preprint":false,"source_species":["Pb"],"role":"primary","match_terms":["SBP1"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"30576479","id":"PMC_30576479","title":"Plasmodium falciparum protein 'PfJ23' hosts distinct binding sites for major virulence factor 'PfEMP1' and Maurer's cleft marker 'PfSBP1'.","date":"2018","source":"Pathogens and disease","url":"https://pubmed.ncbi.nlm.nih.gov/30576479","citation_count":3,"is_preprint":false,"source_species":["Pb"],"role":"primary","match_terms":["skeleton-binding protein 1","PfSBP1"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"38864616","id":"PMC_38864616","title":"Transcriptional responses of brain endothelium to Plasmodium falciparum patient-derived isolates in vitro.","date":"2024","source":"Microbiology spectrum","url":"https://pubmed.ncbi.nlm.nih.gov/38864616","citation_count":1,"is_preprint":false,"source_species":["Pb"],"role":"primary","match_terms":["skeleton-binding protein 1"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"31356937","id":"PMC_31356937","title":"CX3CL1 binding protein-2 (CBP2) of Plasmodium falciparum binds nucleic acids.","date":"2019","source":"International journal of biological macromolecules","url":"https://pubmed.ncbi.nlm.nih.gov/31356937","citation_count":1,"is_preprint":false,"source_species":["Pb"],"role":"primary","match_terms":["PfSBP1"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"38331312","id":"PMC_38331312","title":"Skeleton binding protein 1 localizes to the Maurer's cleft and interacts with PfHSP70-1 and PfHSP70-x in Plasmodium falciparum gametocyte-infected erythrocytes.","date":"2024","source":"Parasitology international","url":"https://pubmed.ncbi.nlm.nih.gov/38331312","citation_count":0,"is_preprint":false,"source_species":["Pb"],"role":"primary","match_terms":["SBP1","skeleton-binding protein 1"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"32495606","id":"PMC_32495606","title":"[Method for rapid synchronization of different growth cycles of Plasmodium falciparum in vitro and application in differential gene expression profile of 3D7 after dihydroartemisinin treatment].","date":"2020","source":"Zhongguo Zhong yao za zhi = Zhongguo zhongyao zazhi = China journal of Chinese materia medica","url":"https://pubmed.ncbi.nlm.nih.gov/32495606","citation_count":0,"is_preprint":false,"source_species":["Pb"],"role":"primary","match_terms":["SBP1","PfSBP1"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":20313,"output_tokens":6537,"usd":0.079497,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":13631,"output_tokens":5792,"usd":0.106478,"stage2_stop_reason":"end_turn"},"total_usd":0.185975,"stage1_batch_id":"msgbatch_01DbiymDmubkPpYvdbAu5a7V","stage2_batch_id":"msgbatch_012TbrWvMRH129T7PQ4SmvrJ","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2000,\n      \"finding\": \"SBP1 (PfSBP1) is an integral membrane protein of Maurer's clefts in P. falciparum-infected erythrocytes; its carboxy-terminal domain, exposed in the host cell cytoplasm, interacts with a 35 kDa erythrocyte skeletal protein, suggesting it participates in anchoring Maurer's clefts to the erythrocyte submembrane skeleton. Antibodies to both termini of PfSBP1 also labelled vesicular structures in P. berghei-infected erythrocytes, indicating conservation across malaria species.\",\n      \"method\": \"Immunoprecipitation with hyperimmune sera, biochemical characterization, antibody labelling of infected erythrocytes from multiple Plasmodium species\",\n      \"journal\": \"Molecular and biochemical parasitology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — single Co-IP/pulldown identifying a 35 kDa partner without its identity; cross-species antibody labelling supports conservation; single lab\",\n      \"pmids\": [\"11087921\"],\n      \"is_preprint\": false,\n      \"attribution\": [\n        {\"species\": \"Plasmodium falciparum\", \"strain\": \"\"},\n        {\"species\": \"Plasmodium berghei\", \"strain\": \"\"},\n        {\"species\": \"Plasmodium chabaudi\", \"strain\": \"\"}\n      ]\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"Targeted gene disruption of SBP1 in P. falciparum prevented PfEMP1 surface expression on infected red blood cells and abolished cytoadhesion; PfEMP1 was retained in Maurer's clefts and Maurer's clefts were displaced from the erythrocyte periphery. Complementation with sbp1 restored PfEMP1 surface expression and adhesion, demonstrating SBP1 is essential for PfEMP1 translocation to the infected erythrocyte surface.\",\n      \"method\": \"Targeted gene disruption (knockout), genetic complementation, immunofluorescence, adhesion assays\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — clean KO with defined cellular phenotype, genetic complementation confirming specificity, replicated by multiple orthogonal assays\",\n      \"pmids\": [\"16520384\"],\n      \"is_preprint\": false,\n      \"attribution\": [\n        {\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}\n      ]\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"PfSBP1 functions at the parasitophorous vacuole membrane (PVM) to load PfEMP1 into Maurer's clefts during formation of these structures; loss of PfSBP1 abolished PfEMP1 surface display and the major antibody reactivity of multigravid women directed at PfEMP1.\",\n      \"method\": \"Genetic disruption of SBP1, immunofluorescence microscopy, antibody reactivity assays with immune sera\",\n      \"journal\": \"Blood\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic loss-of-function with defined pathway placement at PVM, consistent with PMID 16520384, two independent labs\",\n      \"pmids\": [\"17023587\"],\n      \"is_preprint\": false,\n      \"attribution\": [\n        {\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}\n      ]\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"Parasite protein phosphatase 1 (PP1), localized to Maurer's clefts, modulates the phosphorylation status of the amino-terminal domain of PfSBP1 within the lumen of Maurer's clefts, as shown by co-immunoprecipitation and phosphatase inhibition. Hyperphosphorylation of PfSBP1 induced by the PP1 inhibitor calyculin A in late schizonts prevented merozoite release, linking SBP1 phosphorylation state to red blood cell membrane stability.\",\n      \"method\": \"Co-immunoprecipitation, pharmacological inhibition with calyculin A, observation of merozoite release block\",\n      \"journal\": \"Cellular microbiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — single lab Co-IP plus pharmacological inhibitor phenotype; phosphorylation site mapping not performed at atomic resolution\",\n      \"pmids\": [\"16548885\"],\n      \"is_preprint\": false,\n      \"attribution\": [\n        {\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}\n      ]\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"The carboxy-terminal cytoplasmic domain of PfSBP1 on Maurer's clefts interacts with the host erythrocyte cytosolic protein LANCL1; LANCL1 is specifically recruited to the surface of Maurer's clefts in mature P. falciparum blood stages, implicating this interaction in preventing premature rupture of the red blood cell membrane.\",\n      \"method\": \"Co-immunoprecipitation, mass spectrometry identification of LANCL1, immunofluorescence localization in infected erythrocytes\",\n      \"journal\": \"Molecular and biochemical parasitology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — Co-IP with MS identification of partner and localization; single lab, functional inference not directly tested\",\n      \"pmids\": [\"15811525\"],\n      \"is_preprint\": false,\n      \"attribution\": [\n        {\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}\n      ]\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"The transmembrane domain of PfSBP1 functions as an internal signal sequence for entry into the parasite's secretory pathway and transport to the parasite plasma membrane; trafficking beyond the parasite plasma membrane additionally requires N-terminal domains with high negative net charge, which influence protein solubility, membrane orientation, and subcellular localization. PfSBP1 lacks the PEXEL/VTS motif and is not N-terminally processed.\",\n      \"method\": \"Domain-deletion mutagenesis, chimeric reporter constructs, biochemical fractionation, immunofluorescence\",\n      \"journal\": \"Traffic (Copenhagen, Denmark)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — mutagenesis with functional readout in multiple constructs, single lab\",\n      \"pmids\": [\"19054387\"],\n      \"is_preprint\": false,\n      \"attribution\": [\n        {\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}\n      ]\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"The N-terminal region and transmembrane domain of PfSBP1 can functionally replace the corresponding regions in the PEXEL-negative exported protein REX2 to promote export, demonstrating these sequence features are shared among PEXEL-negative exported proteins and are functionally interchangeable.\",\n      \"method\": \"Chimeric protein domain-swap constructs expressed in P. falciparum, fluorescence microscopy\",\n      \"journal\": \"Molecular microbiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional domain-swap experiment with defined export readout; single lab\",\n      \"pmids\": [\"19170882\"],\n      \"is_preprint\": false,\n      \"attribution\": [\n        {\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}\n      ]\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"PfSBP1 physically interacts with the molecular chaperone PfBiP during early export steps, as revealed by the conditional aggregation domain (CAD) export system; this interaction occurs prior to arrival at Maurer's clefts.\",\n      \"method\": \"Conditional protein export system (CAD domain fused to full-length PfSBP1), co-immunoprecipitation of intermediate complexes\",\n      \"journal\": \"Cellular microbiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — single Co-IP using engineered conditional system; single lab but novel method\",\n      \"pmids\": [\"18691247\"],\n      \"is_preprint\": false,\n      \"attribution\": [\n        {\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}\n      ]\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Plasmepsin V does not cleave the N-terminal sequence of SBP1 (a PEXEL-negative exported protein), establishing that SBP1 export is independent of Plasmepsin V processing.\",\n      \"method\": \"In vitro Plasmepsin V cleavage assay, N-terminal sequencing\",\n      \"journal\": \"Traffic (Copenhagen, Denmark)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Weak — in vitro enzymatic assay; negative result mechanistically informative; single lab\",\n      \"pmids\": [\"23387285\"],\n      \"is_preprint\": false,\n      \"attribution\": [\n        {\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}\n      ]\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"A defined region of PfSBP1 binds specifically to sub-domains of two major erythrocyte membrane skeleton components, protein 4.1R and spectrin; these interactions anchor Maurer's clefts to the red blood cell membrane skeleton but are necessary yet not sufficient for PfEMP1 translocation to the RBC surface. The N-terminal domain of SBP1 within the Maurer's cleft lumen plays an essential but unidentified additional role.\",\n      \"method\": \"GST pulldown, domain-deletion mapping, binding assays with recombinant erythrocyte skeleton proteins, co-localization\",\n      \"journal\": \"Biochimica et biophysica acta\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — pulldown with domain mapping; binding partners identified; functional sufficiency tested; single lab\",\n      \"pmids\": [\"25883090\"],\n      \"is_preprint\": false,\n      \"attribution\": [\n        {\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}\n      ]\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Three resident Maurer's cleft membrane proteins including PfSBP1 are exported as soluble forms in the red cell cytoplasm and associate with the parasite group II chaperonin PfTRiC; the domain of interaction with PfTRiC was mapped within the amino-terminal domain of PfSBP1.\",\n      \"method\": \"Co-immunoprecipitation, domain mapping, subcellular fractionation\",\n      \"journal\": \"Traffic (Copenhagen, Denmark)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — Co-IP with domain mapping; single lab; proposed general role for PfTRiC supported by data on multiple cleft proteins\",\n      \"pmids\": [\"25615740\"],\n      \"is_preprint\": false,\n      \"attribution\": [\n        {\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}\n      ]\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"P. berghei orthologues of SBP1 and MAHRP1 were identified; red blood cells infected with P. berghei parasites lacking SBP1 fail to bind the endothelial receptor CD36 and show reduced sequestration and virulence in mice. Complementation of P. berghei SBP1 knockout parasites with P. falciparum SBP1 restored sequestration and virulence, demonstrating evolutionary conservation of SBP1 function across divergent malaria parasites.\",\n      \"method\": \"Gene knockout in P. berghei, cross-species complementation with P. falciparum SBP1, in vivo sequestration assays (bioluminescence imaging), CD36 binding assays, virulence assessment in mice\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic KO with defined cellular phenotype, cross-species functional complementation, multiple orthogonal in vivo readouts\",\n      \"pmids\": [\"27225796\"],\n      \"is_preprint\": false,\n      \"attribution\": [\n        {\"species\": \"Plasmodium berghei\", \"strain\": \"\"},\n        {\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}\n      ]\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Genetic deletion of SBP1 in P. falciparum dramatically reduced antibody recognition of infected erythrocytes and abolished the ability of human antibodies to promote opsonic phagocytosis, demonstrating that SBP1 is part of a critical trafficking pathway for the dominant surface antigens (primarily PfEMP1) targeted by acquired human immunity.\",\n      \"method\": \"Genetic deletion of SBP1, flow cytometry-based antibody binding assays, opsonic phagocytosis assays, multiple parasite isolates and immune sera from different populations\",\n      \"journal\": \"Cellular and molecular life sciences : CMLS\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — clean KO with multiple orthogonal functional assays; replicated across multiple parasite isolates and population cohorts\",\n      \"pmids\": [\"27193441\"],\n      \"is_preprint\": false,\n      \"attribution\": [\n        {\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}\n      ]\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"P. knowlesi SBP1 (PkSBP1), when expressed as an epitope-tagged recombinant protein, localizes to membranous structures (Sinton and Mulligan stipplings) analogous to Maurer's clefts in monkey and human erythrocytes; when expressed in P. falciparum-infected erythrocytes, PkSBP1 co-localizes with PfSBP1 at Maurer's clefts, demonstrating conservation of the trafficking pathway.\",\n      \"method\": \"Transgenic parasite expression of epitope-tagged PkSBP1, immunofluorescence assay, immunoelectron microscopy, co-localization with PfSBP1\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct localization by IFA and immuno-EM with functional implication of conserved trafficking; single lab\",\n      \"pmids\": [\"27732628\"],\n      \"is_preprint\": false,\n      \"attribution\": [\n        {\"species\": \"Plasmodium knowlesi\", \"strain\": \"\"}\n      ]\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"PHISTc protein PFD1140w interacts with both PfSBP1 and PfEMP1 simultaneously in vitro, forming a tripartite complex; a direct binding interaction between recombinant PHIST proteins and PfSBP1 was detected, identifying PfSBP1 as a novel binding partner of PHISTc family members.\",\n      \"method\": \"In vitro pulldown/binding assays with recombinant proteins, co-immunoprecipitation, co-localization by immunofluorescence\",\n      \"journal\": \"The FEBS journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — in vitro binding with recombinant proteins and Co-IP; tripartite complex formation demonstrated; single lab\",\n      \"pmids\": [\"29155505\"],\n      \"is_preprint\": false,\n      \"attribution\": [\n        {\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}\n      ]\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Using time-resolved proximity biotinylation (SBP1 fused to TurboID), two groups of SBP1 interactors were identified: early (pre-export) and late (post-export). Two membrane-associated proteins were identified as pre-export interactors, one with a predicted translocon domain, suggesting they facilitate extraction of SBP1 from the parasite plasma membrane for export.\",\n      \"method\": \"TurboID proximity biotinylation fused to SBP1, label-free quantitative proteomics, conditional mutants of candidate proteins, fluorescence localization\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — proximity biotinylation proteomics with temporal resolution; candidate validation by conditional mutants; single lab\",\n      \"pmids\": [\"37772444\"],\n      \"is_preprint\": false,\n      \"attribution\": [\n        {\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}\n      ]\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"A comprehensive SBP1 interactome was determined in P. falciparum-infected erythrocytes using unbiased proteomic approaches; SBP1 interactomes revealed numerous exported proteins and potential interactors associated with SBP1 intracellular trafficking, including host-parasite protein interactions. The exported protein MAL8P1.4 was linked to P. falciparum virulence via this interaction network.\",\n      \"method\": \"Proteomic interaction mapping (co-immunoprecipitation/AP-MS), label-free quantitative mass spectrometry\",\n      \"journal\": \"iScience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — comprehensive AP-MS interactome; single lab; individual interactions not validated by orthogonal methods\",\n      \"pmids\": [\"31476617\"],\n      \"is_preprint\": false,\n      \"attribution\": [\n        {\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}\n      ]\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"SBP1 accumulates in electron-dense material (EDM) in the parasite cytoplasm during the early trophozoite (ring form) stage and is subsequently found in the parasitophorous vacuolar (PV) space before translocation to Maurer's clefts, defining an intermediate trafficking step for SBP1 export.\",\n      \"method\": \"Immunoelectron microscopy with anti-SBP1 antibodies raised against recombinant PfSBP1\",\n      \"journal\": \"Parasitology international\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct ultrastructural localization by immunoelectron microscopy; single lab; defines trafficking intermediate\",\n      \"pmids\": [\"31669509\"],\n      \"is_preprint\": false,\n      \"attribution\": [\n        {\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}\n      ]\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"SBP1 and MAHRP2 assume a lumenal topology within the parasite secretory pathway (ER lumen), forming ER-lumenal intermediates during export; addition of a C-terminal KDEL ER-retention sequence enhanced retention of SBP1 in the parasite ER, indicating that a sub-population of SBP1 adopts an ER-lumenal state that is a productive intermediate in the export process. SBP1 is targeted by an internal hydrophobic sequence that, unlike a transmembrane segment, does not span the ER membrane.\",\n      \"method\": \"Chimeric reporter constructs with ER-retention sequences, intact-cell topology assays, fluorescence microscopy, mass spectrometry\",\n      \"journal\": \"PLoS pathogens\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple chimeric constructs with functional retention assays and topology determination; novel mechanistic insight; single lab\",\n      \"pmids\": [\"37000891\"],\n      \"is_preprint\": false,\n      \"attribution\": [\n        {\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}\n      ]\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"SBP1 is expressed in gametocyte-infected erythrocytes and localizes to dot-like Maurer's cleft structures in their cytoplasm; co-immunoprecipitation followed by mass spectrometry identified PfHSP70-1 and PfHSP70-x as SBP1-interacting molecular chaperones in gametocyte-infected erythrocytes, with some HSP70 co-localizing in a dot-like cytoplasmic pattern in immature gametocytes.\",\n      \"method\": \"Co-immunoprecipitation, mass spectrometry, immunofluorescence localization in gametocyte-infected erythrocytes\",\n      \"journal\": \"Parasitology international\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — Co-IP/MS identification of chaperone partners with supporting localization; single lab; gametocyte stage not previously characterized for SBP1\",\n      \"pmids\": [\"38331312\"],\n      \"is_preprint\": false,\n      \"attribution\": [\n        {\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}\n      ]\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Direct in vitro interaction was demonstrated between purified PfSBP1 and recombinant PfJ23 (a PEXEL-positive hyp16 family member); PfJ23, PfSBP1 and PfEMP1 can form a tripartite complex in vitro, and PfJ23 partially co-localizes with PfSBP1 in parasite-infected erythrocytes.\",\n      \"method\": \"In vitro pulldown with recombinant proteins, co-immunoprecipitation with native proteins, immunofluorescence co-localization\",\n      \"journal\": \"Pathogens and disease\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single lab, single Co-IP/pulldown, functional implication proposed but not directly tested\",\n      \"pmids\": [\"30576479\"],\n      \"is_preprint\": false,\n      \"attribution\": [\n        {\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}\n      ]\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"The cytoplasmic domain of CBP2 (cCBP2) interacts in vitro with PfSBP1; this interaction is influenced by ATP binding to cCBP2, which induces structural changes in the protein.\",\n      \"method\": \"In vitro binding assay with recombinant proteins, biophysical characterization\",\n      \"journal\": \"International journal of biological macromolecules\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single in vitro binding assay; single lab; no cellular validation of interaction\",\n      \"pmids\": [\"31356937\"],\n      \"is_preprint\": false,\n      \"attribution\": [\n        {\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}\n      ]\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"SBP1 KO P. berghei parasites (lacking sequestration ability) induced similar early lung pathology as wild-type parasites in experimental MA-ARDS, but lung pathology resolved in >60% of SBP1 KO-infected mice, associated with decreased inflammatory cytokine expression and lower cytotoxic CD8+ T cell markers; this establishes that SBP1-mediated sequestration inhibits spontaneous disease resolution rather than being required for initial pathology.\",\n      \"method\": \"SBP1 KO P. berghei in vivo mouse model, bioluminescence imaging, RT-qPCR (parasite load and cytokines), flow cytometry for CD8+ T cells, histopathology\",\n      \"journal\": \"PLoS pathogens\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — clean genetic KO with multiple in vivo readouts; mechanistic pathway placement via epistasis; single lab\",\n      \"pmids\": [\"34843584\"],\n      \"is_preprint\": false,\n      \"attribution\": [\n        {\"species\": \"Plasmodium berghei\", \"strain\": \"NK65\"}\n      ]\n    }\n  ],\n  \"current_model\": \"SBP1 (PBANKA_1101300/PfSBP1) is an integral membrane protein of Maurer's clefts that traffics through an ER-lumenal intermediate and the parasitophorous vacuole membrane to reach its destination; its transmembrane domain serves as an internal signal sequence for secretory pathway entry, while N-terminal negatively charged domains govern membrane orientation and export competence; at the Maurer's cleft, SBP1 is essential for translocation of PfEMP1 to the infected erythrocyte surface (likely by anchoring Maurer's clefts to the host membrane skeleton via interactions with protein 4.1R and spectrin), interacts with host LANCL1, parasite chaperones PfTRiC, PfBiP, PfHSP70-1, and PfHSP70-x, and PHISTc/PfJ23 family exported proteins; its phosphorylation state is modulated by a cleft-resident PP1 phosphatase; and its function is evolutionarily conserved in P. berghei, where SBP1 mediates parasite sequestration, virulence, and inhibition of spontaneous resolution of malaria-associated acute respiratory distress syndrome.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"SBP1 (PBANKA_1101300/PfSBP1) is an integral membrane protein resident at the Maurer's clefts of malaria parasite-infected erythrocytes that is essential for the export machinery delivering parasite virulence antigens to the host red-cell surface [#0, #1]. Genetic disruption of SBP1 in P. falciparum retains PfEMP1 within Maurer's clefts, abolishes its surface display and cytoadhesion, and is rescued by complementation, establishing SBP1 as an indispensable component of the PfEMP1 translocation pathway acting during cleft formation at the parasitophorous vacuole membrane [#1, #2]; loss of SBP1 correspondingly collapses antibody recognition and opsonic phagocytosis of infected cells, placing it upstream of the dominant surface antigens targeted by acquired immunity [#12]. SBP1 anchors Maurer's clefts to the erythrocyte membrane skeleton through its C-terminal cytoplasmic domain, which binds a 35 kDa skeletal protein and, more specifically, sub-domains of protein 4.1R and spectrin, an interaction necessary but not sufficient for PfEMP1 surface delivery, while an essential lumenal role for its N-terminal domain remains uncharacterized [#0, #9]. SBP1 reaches the clefts via a distinctive PEXEL/VTS-independent, Plasmepsin V-independent route: its internal hydrophobic segment serves as an internal signal for secretory-pathway entry and transits an ER-lumenal intermediate, with N-terminal negatively charged domains governing membrane orientation and export competence [#5, #8, #18]. This trafficking is chaperone-dependent, engaging PfBiP and the group II chaperonin PfTRiC during early soluble export intermediates and passing through electron-dense cytoplasmic material and the parasitophorous vacuolar space before cleft delivery [#7, #10, #17]. SBP1 function is deeply conserved: cross-species complementation with P. falciparum SBP1 restores CD36 binding, sequestration and virulence in P. berghei SBP1 knockouts, and in a P. berghei model SBP1-mediated sequestration inhibits spontaneous resolution of malaria-associated acute respiratory distress syndrome rather than driving initial pathology [#11, #22].\",\n  \"teleology\": [\n    {\n      \"year\": 2000,\n      \"claim\": \"Establishing that SBP1 is a Maurer's cleft integral membrane protein whose cytoplasmic C-terminus engages the host skeleton framed it as a candidate linker between parasite-induced structures and the erythrocyte membrane.\",\n      \"evidence\": \"Immunoprecipitation and biochemical characterization plus cross-species antibody labelling of infected erythrocytes\",\n      \"pmids\": [\"11087921\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Identity of the 35 kDa erythrocyte partner not determined\", \"Functional consequence of the anchoring interaction not tested\"],\n      \"attribution\": [\n        {\"species\": \"Plasmodium falciparum\", \"strain\": \"\"},\n        {\"species\": \"Plasmodium berghei\", \"strain\": \"\"},\n        {\"species\": \"Plasmodium chabaudi\", \"strain\": \"\"}\n      ]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Identifying host LANCL1 as a partner of the SBP1 C-terminal cytoplasmic domain extended the anchoring model to specific host cytosolic recruitment at the cleft surface.\",\n      \"evidence\": \"Co-immunoprecipitation with mass spectrometry identification and immunofluorescence in infected erythrocytes\",\n      \"pmids\": [\"15811525\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Proposed role in preventing premature RBC rupture not directly tested\", \"Single lab, no functional loss-of-function of the interaction\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Gene disruption resolved whether SBP1 is merely a structural resident or functionally required, showing it is essential for translocating PfEMP1 to the infected-cell surface and for cytoadhesion, and placing its action at the PVM during cleft formation.\",\n      \"evidence\": \"Targeted knockout with genetic complementation, immunofluorescence, and adhesion/antibody-reactivity assays in P. falciparum\",\n      \"pmids\": [\"16520384\", \"17023587\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular mechanism of PfEMP1 hand-off not defined\", \"Whether SBP1 acts directly on PfEMP1 or indirectly via cleft architecture unresolved\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Linking a cleft-resident PP1 to the phosphorylation state of the SBP1 N-terminal domain connected reversible SBP1 modification to red-cell membrane stability and merozoite release.\",\n      \"evidence\": \"Co-immunoprecipitation and calyculin A inhibition with observation of blocked merozoite release\",\n      \"pmids\": [\"16548885\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Phosphorylation sites not mapped at residue resolution\", \"Direct causal link between SBP1 phosphorylation and release not isolated from other PP1 substrates\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Dissecting the export signals showed SBP1 uses a PEXEL-independent route in which its transmembrane segment acts as an internal signal and negatively charged N-terminal domains license export, defining the sequence logic of a PEXEL-negative exported protein.\",\n      \"evidence\": \"Domain-deletion and chimeric reporter mutagenesis with fractionation and microscopy; domain swaps onto REX2; CAD conditional export system identifying PfBiP interaction\",\n      \"pmids\": [\"19054387\", \"19170882\", \"18691247\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Machinery recognizing the internal signal not identified\", \"Order of chaperone engagement not fully resolved\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"An in vitro cleavage assay confirmed SBP1 export is independent of Plasmepsin V processing, cementing its classification within the PEXEL-negative export pathway.\",\n      \"evidence\": \"In vitro Plasmepsin V cleavage assay with N-terminal sequencing\",\n      \"pmids\": [\"23387285\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Negative in vitro result; alternative processing events not excluded\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Mapping SBP1 binding to protein 4.1R/spectrin sub-domains and to the chaperonin PfTRiC clarified both the host-skeleton anchoring interface and a soluble chaperone-assisted export intermediate, while revealing that skeleton binding is necessary but not sufficient for PfEMP1 surface delivery.\",\n      \"evidence\": \"GST pulldowns and domain mapping with recombinant skeleton proteins; co-IP and fractionation identifying PfTRiC interaction mapped to the N-terminal domain\",\n      \"pmids\": [\"25883090\", \"25615740\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"The additional essential lumenal N-terminal function remains unidentified\", \"Interactions not validated by orthogonal in-cell methods\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Cross-species knockout and complementation established that SBP1 function is evolutionarily conserved, mediating CD36 binding, sequestration and virulence in P. berghei, and that its trafficking pathway underlies immune recognition of infected cells.\",\n      \"evidence\": \"P. berghei knockout with P. falciparum complementation and in vivo sequestration/virulence readouts; P. falciparum deletion coupled to antibody-binding and opsonic phagocytosis assays; PkSBP1 localization by IFA and immuno-EM\",\n      \"pmids\": [\"27225796\", \"27193441\", \"27732628\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Conserved molecular partners across species not fully mapped\", \"How SBP1 loss translates to loss of specific surface antigens beyond PfEMP1 not delineated\"],\n      \"attribution\": [\n        {\"species\": \"Plasmodium berghei\", \"strain\": \"\"},\n        {\"species\": \"Plasmodium falciparum\", \"strain\": \"\"},\n        {\"species\": \"Plasmodium knowlesi\", \"strain\": \"\"}\n      ]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Demonstrating that SBP1 can bind PHISTc protein PFD1140w and PfEMP1 simultaneously identified it as a scaffolding node in a tripartite complex, suggesting how it organizes PfEMP1 within clefts.\",\n      \"evidence\": \"In vitro binding with recombinant proteins, co-IP, and co-localization\",\n      \"pmids\": [\"29155505\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Tripartite complex shown in vitro; physiological stoichiometry and in-cell assembly not established\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Temporal proximity biotinylation, AP-MS interactome mapping, and ultrastructural localization resolved SBP1's export itinerary and its distinct pre- and post-export interactor sets, including a candidate translocon-domain protein and an intermediate through electron-dense material and the PV space.\",\n      \"evidence\": \"TurboID proximity proteomics with conditional mutants; AP-MS interactome; immunoelectron microscopy\",\n      \"pmids\": [\"37772444\", \"31476617\", \"31669509\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct extraction/translocon mechanism at the parasite plasma membrane not proven\", \"Most interactome hits not individually validated\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"An epistasis experiment in an MA-ARDS model showed SBP1-mediated sequestration inhibits spontaneous disease resolution rather than being required for initial lung pathology, refining SBP1's role in disease progression.\",\n      \"evidence\": \"SBP1 knockout P. berghei NK65 mouse model with bioluminescence imaging, cytokine RT-qPCR, CD8+ T-cell flow cytometry, and histopathology\",\n      \"pmids\": [\"34843584\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism linking sequestration to sustained inflammation not defined\", \"Single lab, single strain\"],\n      \"attribution\": [{\"species\": \"Plasmodium berghei\", \"strain\": \"NK65\"}]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Topology analysis revealed a productive ER-lumenal intermediate for SBP1 export, showing its internal hydrophobic sequence does not span the ER membrane and refining the mechanism of secretory-pathway entry.\",\n      \"evidence\": \"Chimeric reporters with KDEL retention, intact-cell topology assays, microscopy and mass spectrometry\",\n      \"pmids\": [\"37000891\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"How the lumenal intermediate is converted to a membrane-integral cleft form not resolved\", \"Single lab\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Extending SBP1 study to gametocytes showed it localizes to cleft-like structures there and associates with PfHSP70-1 and PfHSP70-x, indicating chaperone-assisted handling across life-cycle stages.\",\n      \"evidence\": \"Co-immunoprecipitation with mass spectrometry and immunofluorescence in gametocyte-infected erythrocytes\",\n      \"pmids\": [\"38331312\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Functional role of SBP1 in gametocytes not tested\", \"Chaperone interactions not functionally dissected\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The essential lumenal N-terminal function of SBP1, the direct molecular mechanism by which it hands PfEMP1 to the surface, and the identity of the machinery recognizing its internal export signal remain unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No structure of SBP1 or its complexes\", \"Mechanism of PfEMP1 translocation downstream of skeleton anchoring unknown\", \"Translocon that extracts SBP1 for export not definitively identified\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0005198\", \"supporting_discovery_ids\": [0, 9]},\n      {\"term_id\": \"GO:0051082\", \"supporting_discovery_ids\": [7, 10, 19]},\n      {\"term_id\": \"GO:0005515\", \"supporting_discovery_ids\": [4, 9, 14, 20, 21]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0020030\", \"supporting_discovery_ids\": [0, 1, 13, 17]},\n      {\"term_id\": \"GO:0016020\", \"supporting_discovery_ids\": [0, 5]},\n      {\"term_id\": \"GO:0005788\", \"supporting_discovery_ids\": [18]},\n      {\"term_id\": \"GO:0020002\", \"supporting_discovery_ids\": [2, 17]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"GO:0046903\", \"supporting_discovery_ids\": [5, 6, 8, 18]},\n      {\"term_id\": \"GO:0052192\", \"supporting_discovery_ids\": [1, 2, 12]},\n      {\"term_id\": \"GO:0006886\", \"supporting_discovery_ids\": [5, 7, 10, 17, 18]}\n    ],\n    \"complexes\": [\n      \"SBP1–PHISTc(PFD1140w)–PfEMP1 tripartite complex [#14]\",\n      \"SBP1–PfJ23–PfEMP1 tripartite complex [#20]\"\n    ],\n    \"partners\": [\n      \"Erythrocyte protein 4.1R [#9]\",\n      \"Erythrocyte spectrin [#9]\",\n      \"35 kDa erythrocyte skeletal protein [#0]\",\n      \"Host LANCL1 [#4]\",\n      \"PfBiP [#7]\",\n      \"PfTRiC (group II chaperonin) [#10]\",\n      \"PfHSP70-1 [#19]\",\n      \"PfHSP70-x [#19]\",\n      \"PHISTc PFD1140w [#14]\",\n      \"PfJ23 [#20]\",\n      \"CBP2 cytoplasmic domain [#21]\",\n      \"PfEMP1 (functional/complex partner) [#1, #14, #20]\"\n    ],\n    \"other_free_text\": [\n      \"SBP1 is a PEXEL/VTS-negative exported protein that is not N-terminally processed and whose export is independent of Plasmepsin V [#5, #8].\",\n      \"Its transmembrane/internal hydrophobic segment acts as an internal signal for secretory-pathway entry; N-terminal negatively charged domains govern membrane orientation and export competence [#5, #18].\",\n      \"SBP1 phosphorylation state is modulated by a Maurer's-cleft-resident PP1; hyperphosphorylation blocks merozoite release [#3].\",\n      \"SBP1 function is evolutionarily conserved: P. falciparum SBP1 complements P. berghei SBP1 knockouts for sequestration and virulence [#11].\",\n      \"In P. berghei, SBP1-mediated sequestration inhibits spontaneous resolution of malaria-associated acute respiratory distress syndrome rather than driving initial pathology [#22].\"\n    ]\n  }\n}","audit_flag":null,"strains":[{"strain":"PbANKA","gene_id":"PBANKA_1101300","name":null,"product":"skeleton-binding protein 1","uniprot_acc":null,"chromosome":null,"start_pos":null},{"strain":"PkH","gene_id":"PKNH_0102700","name":null,"product":"hypothetical protein","uniprot_acc":null,"chromosome":null,"start_pos":null}],"gene_symbol":"SBP1","evaluation":null}