{"gene":"PF3D7_1471100","run_date":"2026-09-08T14:19:07","timeline":{"discoveries":[{"year":2009,"finding":"EXP2 was identified as the membrane-associated, pore-forming component of the PTEX (Plasmodium translocon of exported proteins) complex, which is located in the parasitophorous vacuole membrane (PVM) and is ATP-powered. EXP2 forms part of a core complex with HSP101 and PTEX150.","method":"Co-immunoprecipitation, mass spectrometry, biochemical fractionation, and immunolocalization","journal":"Nature","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal Co-IP and MS identification of complex, replicated across multiple subsequent studies","pmids":["19536257"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":1994,"finding":"EXP2 (35 kDa protein) was identified as a membrane protein tightly associated with the parasitophorous vacuole membrane and membrane-bound compartments in the infected erythrocyte cytoplasm, resistant to alkali extraction but soluble in detergent, and co-localizing with EXP1.","method":"Monoclonal antibody characterization, biochemical fractionation, immunolocalization","journal":"Parasitology","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — biochemical fractionation and immunolocalization with functional characterization, single lab","pmids":["8058359"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":1998,"finding":"EXP2 gene was cloned and characterized: it is encoded by a single-copy gene on chromosome 14, transcribed during the ring stage, contains an N-terminal signal sequence that is cleaved from the mature protein, and lacks a typical hydrophobic transmembrane domain. EXP2 may associate with the vacuolar membrane via an amphipathic helix in the N-terminal half.","method":"Gene cloning, PCR, cDNA/genomic sequencing, N-terminal microsequencing, hydrophobicity analysis","journal":"Molecular and biochemical parasitology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct cloning and sequencing with structural inference from sequence analysis, single lab","pmids":["9574909"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2012,"finding":"EXP2 is synthesized earlier in the life cycle than other PTEX components (HSP101 and PTEX150), resides in dense granules of invasive merozoites, and is released into the host cell upon invasion to reside in the PVM with little turnover. EXP2 forms an ~600 kDa apparently homo-oligomeric complex that can be separated from HSP101 and PTEX150 using non-ionic detergents, and biochemical evidence supports an EXP2–PTEX150–HSP101 association order with EXP2 at the vacuolar membrane.","method":"Pulse-chase labeling, immunofluorescence, subcellular fractionation, native gel electrophoresis, non-ionic detergent separation","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal biochemical methods (pulse-chase, fractionation, native PAGE, detergent separation) in single focused study with rigorous controls","pmids":["22253438"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2013,"finding":"EXP2, PTEX150, and HSP101 could not be genetically deleted in Plasmodium berghei, consistent with essential roles during blood-stage development.","method":"Repeated gene deletion attempts (genetic knockout) in P. berghei","journal":"Molecular microbiology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple independent failed deletion attempts in P. berghei, negative result establishing essentiality","pmids":["23869529"],"is_preprint":false,"attribution":[{"species":"Plasmodium berghei","strain":""}]},{"year":2013,"finding":"Repeated attempts to delete exp2 in Plasmodium berghei failed, suggesting EXP2 performs an essential function during blood-stage development.","method":"Gene deletion attempts in P. berghei","journal":"Molecular and biochemical parasitology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — repeated failed gene deletion, independent replication of essentiality finding","pmids":["24076174"],"is_preprint":false,"attribution":[{"species":"Plasmodium berghei","strain":""}]},{"year":2013,"finding":"Three-dimensional structured illumination microscopy showed that EXP2, as part of PTEX complexes, localizes in dynamic foci at the PVM and that exported proteins spatially associate with EXP2 during both native conditions and upon generation of translocation intermediates, providing direct cellular evidence that protein export occurs at PVM regions housing PTEX.","method":"3D structured illumination microscopy (3D-SIM), live imaging of purified merozoites, translocation intermediate generation","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 2 / Strong — super-resolution live imaging with functional translocation intermediate assay, multiple orthogonal approaches","pmids":["23361006"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2015,"finding":"Conditional deletion of EXP2 using the FLP/FRT system in P. berghei showed that EXP2 is important for parasite growth in the liver and critical for transition to blood-stage infection. EXP2-deficient parasites were severely impaired in generating patent blood-stage infection.","method":"FLP/FRT conditional mutagenesis, mouse infection experiments","journal":"Cellular microbiology","confidence":"High","confidence_rationale":"Tier 2 / Strong — conditional genetic knockout with in vivo phenotypic characterization across liver and blood stages","pmids":["26347246"],"is_preprint":false,"attribution":[{"species":"Plasmodium berghei","strain":""}]},{"year":2015,"finding":"In P. berghei, fluorescent tagging of EXP2 revealed its prominent presence at the parasite periphery and in motile, tubular extensions of the parasitophorous vacuole that protrude far into the red blood cell, consistent with EXP2's proposed role in pore formation.","method":"Endogenous fluorescent tagging, live cell imaging, correlative light and electron microscopy","journal":"Scientific reports","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — direct localization by live imaging with endogenous tagging, single lab","pmids":["26219962"],"is_preprint":false,"attribution":[{"species":"Plasmodium berghei","strain":""}]},{"year":2015,"finding":"In P. yoelii-infected reticulocytes, EXP2 localizes not only to the PVM but also to distinct membrane-bound vesicles in the reticulocyte cytoplasm, in contrast to P. falciparum in mature RBCs where EXP2 is exclusively at the PVM. This cytoplasmic vesicle localization was primarily seen in CD71+ reticulocytes versus mature RBCs, and the pyexp2 gene was refractory to deletion.","method":"Immunofluorescence, proteomic screen, transgenic HA-tagging, conditional deletion attempts","journal":"Eukaryotic cell","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — direct localization experiments in multiple species with host-cell context comparison, single lab","pmids":["25662767"],"is_preprint":false,"attribution":[{"species":"Plasmodium yoelii","strain":"17X"},{"species":"Plasmodium berghei","strain":""},{"species":"Plasmodium falciparum","strain":""}]},{"year":2016,"finding":"Constructs of exported proteins arrested during translocation across the PVM were found in complex with EXP2, providing the first functional evidence that EXP2 is part of a translocating entity at the PVM. Clogging of the translocation pore by these stable intermediates prevented export of all exported protein types and inhibited parasite growth. Two successive translocation steps (one at the parasite plasma membrane and one at the PVM) are required for transmembrane protein export.","method":"Conditionally foldable domain (DHFR) constructs, co-immunoprecipitation of translocation intermediates with EXP2, parasite growth assays","journal":"PLoS pathogens","confidence":"High","confidence_rationale":"Tier 2 / Strong — translocation intermediate trapping with Co-IP of intermediates with EXP2, functional growth assay, multiple substrate types tested","pmids":["27168322"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2016,"finding":"Recombinant EXP2 expressed in E. coli (as a GST fusion) forms pores in bilayer lipid membranes. The inner pore diameter is approximately 3.5 nm based on electron microscopy and channel current measurements. The pore comprises approximately 10–12 EXP2 subunits as determined by size exclusion chromatography and blue native PAGE.","method":"Recombinant protein expression, bilayer lipid membrane electrophysiology, electron microscopy, size exclusion chromatography, blue native PAGE","journal":"Biochemical and biophysical research communications","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro reconstitution of pore activity with multiple orthogonal structural and functional methods, single lab","pmids":["27865834"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2018,"finding":"Cryo-electron microscopy structures of the endogenous PTEX core complex at near-atomic resolution showed that EXP2 and PTEX150 interdigitate to form a static, funnel-shaped pseudo-seven-fold-symmetric protein-conducting channel spanning the vacuolar membrane. EXP2 and PTEX150 form the static channel component, while the AAA+ HSP101 hexamer is tethered above this funnel and undergoes conformational changes for cargo threading.","method":"Cryo-electron microscopy, CRISPR-Cas9 epitope tagging for endogenous complex isolation, structural analysis of 'engaged' and 'resetting' states","journal":"Nature","confidence":"High","confidence_rationale":"Tier 1 / Strong — near-atomic cryo-EM structure of endogenous complex in functional states, with CRISPR-validated endogenous tagging","pmids":["30150771"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2018,"finding":"Using regulated gene expression (TetR-aptamer knockdown), mutagenesis, and cell-attached patch-clamp electrophysiology, EXP2 was shown to serve dual roles: as a protein-conducting channel in the context of PTEX and as a channel facilitating nutrient passage across the PVM independent of HSP101.","method":"TetR-aptamer conditional knockdown, patch-clamp electrophysiology, mutagenesis, protein export assays","journal":"Nature microbiology","confidence":"High","confidence_rationale":"Tier 1 / Strong — multiple orthogonal methods including electrophysiology, conditional knockdown, and mutagenesis establishing dual channel function","pmids":["30150733"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2018,"finding":"Inducible knockdown of EXP2 in P. falciparum blood stages strongly reduced parasite growth proportional to degree of knockdown, stalled development midway through the asexual cycle, and caused severe attenuation of protein export of a tracked exported protein. Growth recovered upon restoration of EXP2 expression.","method":"Inducible knockdown (glmS ribozyme system), parasite growth assays, exported protein trafficking assay","journal":"PloS one","confidence":"High","confidence_rationale":"Tier 2 / Strong — conditional knockdown with dose-dependent phenotype and direct export assay, multiple readouts","pmids":["30439948"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2018,"finding":"When cargo proteins were trapped at the parasite surface, loop-like extensions appeared at the PVM containing both trapped cargo and EXP2, but not HSP101 or PTEX150, suggesting EXP2 can be redistributed to these extensions independently of the full PTEX complex.","method":"DHFR-based export block, structured illumination microscopy, immunofluorescence","journal":"Traffic (Copenhagen, Denmark)","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — super-resolution imaging of EXP2 localization under export-blocked conditions, single lab","pmids":["29696751"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2019,"finding":"Biochemical analysis of EXP2 revealed that cysteines C113 and C140 form an intramolecular disulfide bond while C201 is predominantly reduced. EXP2 has a protease-resistant, membrane-associated N-terminal region (~20 kDa) that does not project into the erythrocyte cytosol, while its C-terminus projects into the vacuole space. A transmembrane peptide from the N-terminal region is hemolytic and forms a discrete pore in an osmotic protection assay.","method":"Differential alkylation, protease protection assay, hemolysis assay, osmotic protection assay with synthetic peptide","journal":"Journal of biochemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — multiple in vitro biochemical and functional assays establishing topology and pore-forming activity of EXP2 N-terminus","pmids":["30476118"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2019,"finding":"Loss of EXP1 caused loss of correct localization of EXP2 at the PVM and abolished the nutrient-permeable channel activity of the PVM without affecting protein export, demonstrating that EXP1 is specifically required for functional expression of EXP2 as the nutrient-permeable channel.","method":"Conditional EXP1 knockout, patch-clamp electrophysiology, protein export assays, immunofluorescence","journal":"PLoS biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — conditional KO with electrophysiology and direct export assays, multiple orthogonal methods","pmids":["31568532"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2020,"finding":"EXP1 knockdown substantially altered the distribution of EXP2 within the PVM but did not impact the distribution of HSP101, revealing that EXP1 is required for proper organization of EXP2 within the PVM.","method":"CRISPR/Cpf1-mediated conditional knockdown (TetR-DOZI-aptamers), BioID2 proximity labeling, immunofluorescence, electron microscopy","journal":"Cellular microbiology","confidence":"High","confidence_rationale":"Tier 2 / Strong — conditional knockdown with proximity labeling and ultrastructural analysis, orthogonal methods","pmids":["31990132"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2020,"finding":"EXP2 is excluded from micrometer-sized contact sites of close apposition between the PVM and parasite plasma membrane (contacting domains), while the lipid transporter PfNCR1 is included in these regions, demonstrating spatial segregation of the hydrophilic nutrient/protein channel EXP2 from a hydrophobic substrate transporter.","method":"Super-resolution fluorescence microscopy, electron microscopy, subcellular localization of tagged proteins","journal":"Nature communications","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — direct localization by imaging showing EXP2 exclusion from contact domains, single lab","pmids":["32732874"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2020,"finding":"EXP2 is a pore-forming protein secreted from sporozoites upon contact with the host cell milieu, and EXP2 is critical for hepatocyte invasion. EXP2-deficient sporozoites are impaired in invasion, rescued by exogenous recombinant EXP2 or alpha-hemolysin (a pore-forming protein), and by acid sphingomyelinase, indicating that EXP2's pore-forming activity induces hepatocyte membrane repair, which facilitates parasite invasion.","method":"Genetic deletion, recombinant protein rescue, chemical inhibition and genetic knockdown of acid sphingomyelinase, invasion assays","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic deletion with rescue by exogenous EXP2 and functional analog, multiple orthogonal approaches","pmids":["33159090"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2021,"finding":"EXP2 forms part of a translocation intermediate complex with core PTEX components (HSP101 and PTEX150) during export of the integral membrane protein SURFIN4.1 (mini-SURFIN4.1). A processed form of Pf113 also associates with EXP2 in stable translocation intermediates at the parasite plasma membrane.","method":"Co-immunoprecipitation of translocation intermediates, structured illumination microscopy","journal":"Parasitology international","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — Co-IP of translocation intermediates, single lab, single method","pmids":["33901679"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2022,"finding":"EXP2 and PTEX150 form a stable subcomplex that facilitates HSP101 docking onto PTEX. This EXP2-PTEX150 subcomplex is a functional assembly unit within the translocon.","method":"Biochemical fractionation, co-immunoprecipitation, immunofluorescence showing HSP101 in parasite ER and PV","journal":"PLoS pathogens","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — Co-IP demonstrating EXP2-PTEX150 subcomplex, single lab, partially supported by localization data","pmids":["35192672"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2022,"finding":"Postinvasion knockdown of EXP2 using the glmS ribozyme in P. berghei reduced parasite size during intrahepatic development and largely abolished expression of the mid-to-late liver-stage marker LISP2, demonstrating that EXP2 is important for intrahepatic parasite development independently of its role in invasion.","method":"glmS ribozyme-mediated conditional knockdown after hepatocyte invasion, immunofluorescence, nanoluciferase reporter assays","journal":"mBio","confidence":"High","confidence_rationale":"Tier 2 / Strong — conditional knockdown with temporal separation from invasion, multiple orthogonal readouts (size, marker expression, luciferase)","pmids":["36445080"],"is_preprint":false,"attribution":[{"species":"Plasmodium berghei","strain":""}]},{"year":2023,"finding":"ER sequestration (knockER) of EXP2 using inducible KDEL fusion demonstrated that EXP2 can be redistributed from the PV to the ER, establishing EXP2's secretory pathway trafficking and enabling loss-of-function studies for vacuolar EXP2.","method":"DiCre-mediated inducible KDEL ER-retrieval (knockER), fluorescence microscopy, parasite growth assays","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — novel conditional ER-sequestration approach applied to EXP2, single lab, functional consequence of redistribution established","pmids":["37552754"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2024,"finding":"Complementation assays in EXP2 knockdown P. falciparum parasites showed that T. gondii GRA17 (a structural ortholog) cannot complement EXP2's protein export function even when supplemented with EXP2's assembly strand and linker helix. The body region of EXP2 is critical for PTEX assembly and/or EXP2 insertion efficiency into the PVM. Altering timing and abundance of EXP2 expression did not affect protein export but affected parasite viability, indicating EXP2's unique transcriptional profile enables its additional nutrient exchange role.","method":"Transgenic complementation with truncations, hybrids, and heterologous GRA17; protein export assays; parasite growth assays","journal":"Frontiers in cellular and infection microbiology","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vivo complementation with multiple truncation and hybrid constructs, functional export and growth readouts, single lab","pmids":["38282616"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2024,"finding":"FlpL/FRT-mediated disruption of exp2 in P. falciparum sporozoites did not affect sporozoite development in mosquitoes or infectivity of hepatocytes but caused 100% loss of liver parasites by day 6 post-infection, demonstrating that EXP2 is essential for intrahepatic liver-stage growth. Expression of some PEXEL proteins (LISP2, CSP but not LSA3) was reduced in exp2-FRT liver stages.","method":"FlpL/FRT conditional gene excision in sporozoites, humanized mouse liver-stage infection model, immunofluorescence of PEXEL reporter proteins","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 / Strong — conditional genetic disruption in sporozoites with in vivo liver-stage readout, 100% penetrant phenotype, multiple PEXEL protein readouts","pmids":["38968107"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2026,"finding":"An EXP2-fluorescent reporter was used to track PVM integrity during egress, showing that the PVM ruptures at a single site and the rupture rapidly expands from that initial site, releasing merozoites. EXP2 localization allowed real-time monitoring of PVM breakdown relative to exocytosis and RBC membrane rupture.","method":"Live fluorescence imaging of EXP2-fluorescent fusion during egress, conditional mutants of PfERC","journal":"PLoS pathogens","confidence":"Low","confidence_rationale":"Tier 3 / Weak — EXP2 used as a PVM reporter, single lab, single method; finding is about PVM dynamics rather than a mechanistic role of EXP2 itself","pmids":["42113900"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]}],"current_model":"EXP2 (PF3D7_1471100) is the membrane-spanning, pore-forming component of the PTEX translocon at the parasitophorous vacuole membrane (PVM), forming a static funnel-shaped pseudo-seven-fold-symmetric channel together with PTEX150 (as revealed by near-atomic cryo-EM), through which HSP101 threads exported proteins; EXP2 also independently functions as a nutrient-permeable channel across the PVM (dependent on EXP1 for correct localization), forms the pore via its N-terminal ~20 kDa membrane-associated region (with an intramolecular C113–C140 disulfide bond), is essential for blood-stage parasite survival, intrahepatic development, and blood-stage infection establishment, and additionally mediates hepatocyte invasion by sporozoites through its pore-forming activity inducing host membrane repair."},"narrative":{"mechanistic_narrative":"EXP2 (PF3D7_1471100) is the membrane-spanning, pore-forming subunit of the Plasmodium translocon of exported proteins (PTEX) at the parasitophorous vacuole membrane (PVM), where it forms a core complex with PTEX150 and the AAA+ ATPase HSP101 that drives export of parasite proteins into the host erythrocyte [PMID:19536257, PMID:30150771]. Near-atomic cryo-EM of the endogenous complex shows that EXP2 and PTEX150 interdigitate into a static, funnel-shaped pseudo-seven-fold-symmetric protein-conducting channel spanning the vacuolar membrane, over which the HSP101 hexamer is tethered and undergoes conformational cycling to thread cargo [PMID:30150771]; consistent with this, exported proteins arrested during translocation are trapped in complex with EXP2 at the PVM, clogging the pore and blocking export [PMID:27168322, PMID:23361006]. Recombinant EXP2 self-assembles into ~10–12-subunit pores in lipid bilayers, and its protease-resistant, membrane-associated N-terminal ~20 kDa region (bearing a C113–C140 intramolecular disulfide bond) forms the transmembrane, pore-forming element with the C-terminus projecting into the vacuolar space [PMID:27865834, PMID:30476118]. Beyond protein export, EXP2 independently serves as a nutrient-permeable channel across the PVM, a function that requires EXP1 for its correct localization and organization but is separable from HSP101-dependent export [PMID:30150733, PMID:31568532, PMID:31990132]. EXP2 is essential across the life cycle: it is required for blood-stage growth and protein export [PMID:30439948], for intrahepatic liver-stage development [PMID:26347246, PMID:36445080, PMID:38968107], and for hepatocyte invasion by sporozoites, where its pore-forming activity triggers host membrane repair that facilitates entry [PMID:33159090].","teleology":[{"year":1994,"claim":"Establishing that EXP2 is a bona fide PVM-associated membrane protein was the prerequisite for any functional role at the host-parasite interface.","evidence":"Monoclonal antibody characterization, biochemical fractionation, and immunolocalization in P. falciparum","pmids":["8058359"],"confidence":"Medium","gaps":["Function of the PVM association not addressed","No oligomeric or channel activity tested"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":1998,"claim":"Cloning showed EXP2 is a single-copy, ring-stage gene with a cleaved signal sequence and no canonical transmembrane domain, raising the question of how it inserts into the PVM.","evidence":"Gene cloning, sequencing, N-terminal microsequencing, and hydrophobicity analysis in P. falciparum","pmids":["9574909"],"confidence":"Medium","gaps":["Membrane-association mode inferred (amphipathic helix), not experimentally demonstrated","No functional assay of the protein"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2009,"claim":"Discovery of PTEX defined EXP2 as the membrane-associated component of an ATP-powered export machine, placing it at the center of protein trafficking into the host cell.","evidence":"Co-IP, mass spectrometry, biochemical fractionation, and immunolocalization identifying the EXP2–PTEX150–HSP101 core in P. falciparum","pmids":["19536257"],"confidence":"High","gaps":["Whether EXP2 itself conducts cargo not yet shown","Stoichiometry and structure of the channel unknown"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2012,"claim":"Tracing EXP2's biogenesis showed it is made early, stored in merozoite dense granules, and forms a stable ~600 kDa homo-oligomer at the PVM upstream of the other PTEX subunits, defining an assembly order.","evidence":"Pulse-chase, fractionation, native PAGE, and detergent separation in P. falciparum","pmids":["22253438"],"confidence":"High","gaps":["Homo-oligomer architecture not resolved","Nature of EXP2–PTEX150–HSP101 coupling not defined at molecular level"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2013,"claim":"Failure to delete exp2 in P. berghei established that EXP2 is essential for blood-stage development, motivating conditional approaches.","evidence":"Repeated failed gene knockout attempts in P. berghei (two independent studies)","pmids":["23869529","24076174"],"confidence":"Medium","gaps":["Essentiality is a negative genetic result without mechanistic cause","Life-cycle stages beyond blood not addressed here"],"attribution":[{"species":"Plasmodium berghei","strain":""}]},{"year":2013,"claim":"Super-resolution imaging placed protein export spatially at PVM foci containing EXP2, providing direct cellular evidence that translocation occurs where PTEX resides.","evidence":"3D-SIM, live merozoite imaging, and translocation intermediate generation in P. falciparum","pmids":["23361006"],"confidence":"High","gaps":["Does not show EXP2 physically conducting cargo","Dynamics of foci formation not mechanistically explained"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2015,"claim":"Conditional deletion and tagging in P. berghei extended EXP2's essential role beyond blood stage to liver growth and transition to blood-stage infection, and revealed dynamic tubular PVM extensions consistent with pore activity.","evidence":"FLP/FRT conditional mutagenesis, mouse infection, and endogenous fluorescent tagging with CLEM in P. berghei; vesicle localization noted in P. yoelii reticulocytes","pmids":["26347246","26219962","25662767"],"confidence":"High","gaps":["Molecular basis of liver-stage requirement not defined","Species-divergent cytoplasmic vesicle localization in P. yoelii reticulocytes not mechanistically explained"],"attribution":[{"species":"Plasmodium berghei","strain":""},{"species":"Plasmodium yoelii","strain":"17X"},{"species":"Plasmodium falciparum","strain":""}]},{"year":2016,"claim":"Trapping stalled cargo in complex with EXP2 gave the first functional proof that EXP2 is part of the translocating entity, and reconstitution showed EXP2 alone forms a defined pore.","evidence":"DHFR conditional-fold constructs with Co-IP of intermediates and growth assays; recombinant EXP2 pore reconstitution by bilayer electrophysiology, EM, SEC, and BN-PAGE in P. falciparum","pmids":["27168322","27865834"],"confidence":"High","gaps":["Recombinant pore stoichiometry (~10–12) differs from later cryo-EM channel; reconciliation not resolved","Two-step export across PPM and PVM mechanistically defined only in outline"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2018,"claim":"Cryo-EM, conditional knockdown, and electrophysiology together defined the channel architecture and split EXP2's activities into an HSP101-dependent protein-export channel and an HSP101-independent nutrient channel.","evidence":"Near-atomic cryo-EM of endogenous PTEX; TetR-aptamer/glmS knockdown, patch-clamp, mutagenesis, and export assays; SIM of EXP2 loop extensions in P. falciparum","pmids":["30150771","30150733","30439948","29696751"],"confidence":"High","gaps":["How the same channel switches between nutrient and protein conduction not resolved","Gating and selectivity mechanisms not defined"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2019,"claim":"Biochemical topology mapping and EXP1 knockout dissected which part of EXP2 forms the pore and which partner controls its nutrient-channel function.","evidence":"Differential alkylation, protease protection, hemolysis and osmotic protection with synthetic peptide; conditional EXP1 KO with patch-clamp and export assays in P. falciparum","pmids":["30476118","31568532"],"confidence":"High","gaps":["Molecular mechanism by which EXP1 organizes EXP2 not defined","Whether EXP1 acts stoichiometrically or as a chaperone unclear"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2020,"claim":"Localization studies refined EXP2's PVM organization—dependent on EXP1 and excluded from PVM/PPM contact domains—while a new role emerged in sporozoite invasion via pore-induced host membrane repair.","evidence":"CRISPR/Cpf1 EXP1 knockdown with BioID2 and EM; super-resolution imaging of contact domains; sporozoite deletion with recombinant EXP2/alpha-hemolysin/acid sphingomyelinase rescue in P. falciparum","pmids":["31990132","32732874","33159090"],"confidence":"High","gaps":["Mechanistic link between EXP2 pore activity and membrane-repair signaling at hepatocyte surface incompletely defined","Functional consequence of EXP2 exclusion from contact domains unknown"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2022,"claim":"Further studies defined an EXP2–PTEX150 subcomplex as the HSP101 docking platform and demonstrated a liver-stage requirement for EXP2 separable from invasion.","evidence":"Fractionation and Co-IP of the EXP2–PTEX150 subcomplex; postinvasion glmS knockdown in P. berghei with LISP2 marker and luciferase readouts","pmids":["35192672","36445080"],"confidence":"Medium","gaps":["Subcomplex assembly demonstrated by Co-IP only","Liver-stage export cargo dependence not fully enumerated"],"attribution":[{"species":"Plasmodium falciparum","strain":""},{"species":"Plasmodium berghei","strain":""}]},{"year":2024,"claim":"Complementation and conditional sporozoite disruption defined EXP2's body region as critical for PTEX assembly, showed a heterologous ortholog cannot substitute, and confirmed EXP2 is essential for intrahepatic growth after successful invasion.","evidence":"Transgenic complementation with truncations/hybrids/GRA17 and export/growth assays; FlpL/FRT sporozoite disruption with humanized-mouse liver-stage model in P. falciparum; knockER ER-sequestration","pmids":["38282616","38968107","37552754"],"confidence":"High","gaps":["Why GRA17 fails to complement despite structural orthology not fully explained","Precise cargo set required for liver-stage growth incomplete"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":null,"claim":"How EXP2 mechanistically toggles between HSP101-driven protein translocation and HSP101-independent nutrient conduction within a single static channel, and how EXP1 physically organizes it, remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No structure of the nutrient-conducting (HSP101-free) state","Gating/selectivity switch between the two modes undefined","Molecular mechanism of EXP1-dependent organization of EXP2 unknown"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]}],"mechanism_profile":{"molecular_activity":[],"localization":[],"pathway":[],"complexes":["PTEX translocon core complex (EXP2–PTEX150–HSP101)","EXP2–PTEX150 static channel subcomplex","EXP2 ~600 kDa homo-oligomer"],"partners":["PTEX150","HSP101","EXP1 (REQUIRED FOR EXP2 PVM ORGANIZATION AND NUTRIENT-CHANNEL ACTIVITY)"],"other_free_text":["N-terminal ~20 kDa membrane-associated region forms the transmembrane pore; C-terminus projects into the vacuolar space [#16].","Intramolecular C113–C140 disulfide bond, with C201 predominantly reduced [#16].","Recombinant EXP2 forms ~3.5 nm pores of ~10–12 subunits in lipid bilayers [#11].","Cryo-EM defines a static funnel-shaped pseudo-seven-fold-symmetric channel with HSP101 tethered above [#12].","Dual function: HSP101-dependent protein-export channel and HSP101-independent nutrient-permeable channel [#13].","Essential for blood-stage growth/export, intrahepatic liver-stage development, and sporozoite hepatocyte invasion via pore-induced host membrane repair [#14, #23, #26, #20].","Heterologous T. gondii GRA17 cannot complement EXP2's export function; the body region is critical for PTEX assembly/PVM insertion [#25].","Species divergence: in P. yoelii reticulocytes EXP2 also localizes to cytoplasmic vesicles, unlike exclusive PVM localization in P. falciparum mature RBCs [#9]."]}},"prefetch_data":{},"corpus_meta":[{"pmid":"19536257","id":"PMC_19536257","title":"A newly discovered protein export machine in malaria parasites.","date":"2009","source":"Nature","url":"https://pubmed.ncbi.nlm.nih.gov/19536257","citation_count":381,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["EXP2","exported protein 2"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"25043010","id":"PMC_25043010","title":"PTEX 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ATP-powered. EXP2 forms part of a core complex with HSP101 and PTEX150.\",\n      \"method\": \"Co-immunoprecipitation, mass spectrometry, biochemical fractionation, and immunolocalization\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal Co-IP and MS identification of complex, replicated across multiple subsequent studies\",\n      \"pmids\": [\"19536257\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 1994,\n      \"finding\": \"EXP2 (35 kDa protein) was identified as a membrane protein tightly associated with the parasitophorous vacuole membrane and membrane-bound compartments in the infected erythrocyte cytoplasm, resistant to alkali extraction but soluble in detergent, and co-localizing with EXP1.\",\n      \"method\": \"Monoclonal antibody characterization, biochemical fractionation, immunolocalization\",\n      \"journal\": \"Parasitology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — biochemical fractionation and immunolocalization with functional characterization, single lab\",\n      \"pmids\": [\"8058359\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"EXP2 gene was cloned and characterized: it is encoded by a single-copy gene on chromosome 14, transcribed during the ring stage, contains an N-terminal signal sequence that is cleaved from the mature protein, and lacks a typical hydrophobic transmembrane domain. EXP2 may associate with the vacuolar membrane via an amphipathic helix in the N-terminal half.\",\n      \"method\": \"Gene cloning, PCR, cDNA/genomic sequencing, N-terminal microsequencing, hydrophobicity analysis\",\n      \"journal\": \"Molecular and biochemical parasitology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct cloning and sequencing with structural inference from sequence analysis, single lab\",\n      \"pmids\": [\"9574909\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"EXP2 is synthesized earlier in the life cycle than other PTEX components (HSP101 and PTEX150), resides in dense granules of invasive merozoites, and is released into the host cell upon invasion to reside in the PVM with little turnover. EXP2 forms an ~600 kDa apparently homo-oligomeric complex that can be separated from HSP101 and PTEX150 using non-ionic detergents, and biochemical evidence supports an EXP2–PTEX150–HSP101 association order with EXP2 at the vacuolar membrane.\",\n      \"method\": \"Pulse-chase labeling, immunofluorescence, subcellular fractionation, native gel electrophoresis, non-ionic detergent separation\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal biochemical methods (pulse-chase, fractionation, native PAGE, detergent separation) in single focused study with rigorous controls\",\n      \"pmids\": [\"22253438\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"EXP2, PTEX150, and HSP101 could not be genetically deleted in Plasmodium berghei, consistent with essential roles during blood-stage development.\",\n      \"method\": \"Repeated gene deletion attempts (genetic knockout) in P. berghei\",\n      \"journal\": \"Molecular microbiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple independent failed deletion attempts in P. berghei, negative result establishing essentiality\",\n      \"pmids\": [\"23869529\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium berghei\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Repeated attempts to delete exp2 in Plasmodium berghei failed, suggesting EXP2 performs an essential function during blood-stage development.\",\n      \"method\": \"Gene deletion attempts in P. berghei\",\n      \"journal\": \"Molecular and biochemical parasitology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — repeated failed gene deletion, independent replication of essentiality finding\",\n      \"pmids\": [\"24076174\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium berghei\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Three-dimensional structured illumination microscopy showed that EXP2, as part of PTEX complexes, localizes in dynamic foci at the PVM and that exported proteins spatially associate with EXP2 during both native conditions and upon generation of translocation intermediates, providing direct cellular evidence that protein export occurs at PVM regions housing PTEX.\",\n      \"method\": \"3D structured illumination microscopy (3D-SIM), live imaging of purified merozoites, translocation intermediate generation\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — super-resolution live imaging with functional translocation intermediate assay, multiple orthogonal approaches\",\n      \"pmids\": [\"23361006\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Conditional deletion of EXP2 using the FLP/FRT system in P. berghei showed that EXP2 is important for parasite growth in the liver and critical for transition to blood-stage infection. EXP2-deficient parasites were severely impaired in generating patent blood-stage infection.\",\n      \"method\": \"FLP/FRT conditional mutagenesis, mouse infection experiments\",\n      \"journal\": \"Cellular microbiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — conditional genetic knockout with in vivo phenotypic characterization across liver and blood stages\",\n      \"pmids\": [\"26347246\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium berghei\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"In P. berghei, fluorescent tagging of EXP2 revealed its prominent presence at the parasite periphery and in motile, tubular extensions of the parasitophorous vacuole that protrude far into the red blood cell, consistent with EXP2's proposed role in pore formation.\",\n      \"method\": \"Endogenous fluorescent tagging, live cell imaging, correlative light and electron microscopy\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — direct localization by live imaging with endogenous tagging, single lab\",\n      \"pmids\": [\"26219962\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium berghei\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"In P. yoelii-infected reticulocytes, EXP2 localizes not only to the PVM but also to distinct membrane-bound vesicles in the reticulocyte cytoplasm, in contrast to P. falciparum in mature RBCs where EXP2 is exclusively at the PVM. This cytoplasmic vesicle localization was primarily seen in CD71+ reticulocytes versus mature RBCs, and the pyexp2 gene was refractory to deletion.\",\n      \"method\": \"Immunofluorescence, proteomic screen, transgenic HA-tagging, conditional deletion attempts\",\n      \"journal\": \"Eukaryotic cell\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — direct localization experiments in multiple species with host-cell context comparison, single lab\",\n      \"pmids\": [\"25662767\"],\n      \"is_preprint\": false,\n      \"attribution\": [\n        {\"species\": \"Plasmodium yoelii\", \"strain\": \"17X\"},\n        {\"species\": \"Plasmodium berghei\", \"strain\": \"\"},\n        {\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}\n      ]\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Constructs of exported proteins arrested during translocation across the PVM were found in complex with EXP2, providing the first functional evidence that EXP2 is part of a translocating entity at the PVM. Clogging of the translocation pore by these stable intermediates prevented export of all exported protein types and inhibited parasite growth. Two successive translocation steps (one at the parasite plasma membrane and one at the PVM) are required for transmembrane protein export.\",\n      \"method\": \"Conditionally foldable domain (DHFR) constructs, co-immunoprecipitation of translocation intermediates with EXP2, parasite growth assays\",\n      \"journal\": \"PLoS pathogens\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — translocation intermediate trapping with Co-IP of intermediates with EXP2, functional growth assay, multiple substrate types tested\",\n      \"pmids\": [\"27168322\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Recombinant EXP2 expressed in E. coli (as a GST fusion) forms pores in bilayer lipid membranes. The inner pore diameter is approximately 3.5 nm based on electron microscopy and channel current measurements. The pore comprises approximately 10–12 EXP2 subunits as determined by size exclusion chromatography and blue native PAGE.\",\n      \"method\": \"Recombinant protein expression, bilayer lipid membrane electrophysiology, electron microscopy, size exclusion chromatography, blue native PAGE\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro reconstitution of pore activity with multiple orthogonal structural and functional methods, single lab\",\n      \"pmids\": [\"27865834\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Cryo-electron microscopy structures of the endogenous PTEX core complex at near-atomic resolution showed that EXP2 and PTEX150 interdigitate to form a static, funnel-shaped pseudo-seven-fold-symmetric protein-conducting channel spanning the vacuolar membrane. EXP2 and PTEX150 form the static channel component, while the AAA+ HSP101 hexamer is tethered above this funnel and undergoes conformational changes for cargo threading.\",\n      \"method\": \"Cryo-electron microscopy, CRISPR-Cas9 epitope tagging for endogenous complex isolation, structural analysis of 'engaged' and 'resetting' states\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — near-atomic cryo-EM structure of endogenous complex in functional states, with CRISPR-validated endogenous tagging\",\n      \"pmids\": [\"30150771\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Using regulated gene expression (TetR-aptamer knockdown), mutagenesis, and cell-attached patch-clamp electrophysiology, EXP2 was shown to serve dual roles: as a protein-conducting channel in the context of PTEX and as a channel facilitating nutrient passage across the PVM independent of HSP101.\",\n      \"method\": \"TetR-aptamer conditional knockdown, patch-clamp electrophysiology, mutagenesis, protein export assays\",\n      \"journal\": \"Nature microbiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — multiple orthogonal methods including electrophysiology, conditional knockdown, and mutagenesis establishing dual channel function\",\n      \"pmids\": [\"30150733\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Inducible knockdown of EXP2 in P. falciparum blood stages strongly reduced parasite growth proportional to degree of knockdown, stalled development midway through the asexual cycle, and caused severe attenuation of protein export of a tracked exported protein. Growth recovered upon restoration of EXP2 expression.\",\n      \"method\": \"Inducible knockdown (glmS ribozyme system), parasite growth assays, exported protein trafficking assay\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — conditional knockdown with dose-dependent phenotype and direct export assay, multiple readouts\",\n      \"pmids\": [\"30439948\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"When cargo proteins were trapped at the parasite surface, loop-like extensions appeared at the PVM containing both trapped cargo and EXP2, but not HSP101 or PTEX150, suggesting EXP2 can be redistributed to these extensions independently of the full PTEX complex.\",\n      \"method\": \"DHFR-based export block, structured illumination microscopy, immunofluorescence\",\n      \"journal\": \"Traffic (Copenhagen, Denmark)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — super-resolution imaging of EXP2 localization under export-blocked conditions, single lab\",\n      \"pmids\": [\"29696751\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Biochemical analysis of EXP2 revealed that cysteines C113 and C140 form an intramolecular disulfide bond while C201 is predominantly reduced. EXP2 has a protease-resistant, membrane-associated N-terminal region (~20 kDa) that does not project into the erythrocyte cytosol, while its C-terminus projects into the vacuole space. A transmembrane peptide from the N-terminal region is hemolytic and forms a discrete pore in an osmotic protection assay.\",\n      \"method\": \"Differential alkylation, protease protection assay, hemolysis assay, osmotic protection assay with synthetic peptide\",\n      \"journal\": \"Journal of biochemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — multiple in vitro biochemical and functional assays establishing topology and pore-forming activity of EXP2 N-terminus\",\n      \"pmids\": [\"30476118\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Loss of EXP1 caused loss of correct localization of EXP2 at the PVM and abolished the nutrient-permeable channel activity of the PVM without affecting protein export, demonstrating that EXP1 is specifically required for functional expression of EXP2 as the nutrient-permeable channel.\",\n      \"method\": \"Conditional EXP1 knockout, patch-clamp electrophysiology, protein export assays, immunofluorescence\",\n      \"journal\": \"PLoS biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — conditional KO with electrophysiology and direct export assays, multiple orthogonal methods\",\n      \"pmids\": [\"31568532\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"EXP1 knockdown substantially altered the distribution of EXP2 within the PVM but did not impact the distribution of HSP101, revealing that EXP1 is required for proper organization of EXP2 within the PVM.\",\n      \"method\": \"CRISPR/Cpf1-mediated conditional knockdown (TetR-DOZI-aptamers), BioID2 proximity labeling, immunofluorescence, electron microscopy\",\n      \"journal\": \"Cellular microbiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — conditional knockdown with proximity labeling and ultrastructural analysis, orthogonal methods\",\n      \"pmids\": [\"31990132\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"EXP2 is excluded from micrometer-sized contact sites of close apposition between the PVM and parasite plasma membrane (contacting domains), while the lipid transporter PfNCR1 is included in these regions, demonstrating spatial segregation of the hydrophilic nutrient/protein channel EXP2 from a hydrophobic substrate transporter.\",\n      \"method\": \"Super-resolution fluorescence microscopy, electron microscopy, subcellular localization of tagged proteins\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — direct localization by imaging showing EXP2 exclusion from contact domains, single lab\",\n      \"pmids\": [\"32732874\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"EXP2 is a pore-forming protein secreted from sporozoites upon contact with the host cell milieu, and EXP2 is critical for hepatocyte invasion. EXP2-deficient sporozoites are impaired in invasion, rescued by exogenous recombinant EXP2 or alpha-hemolysin (a pore-forming protein), and by acid sphingomyelinase, indicating that EXP2's pore-forming activity induces hepatocyte membrane repair, which facilitates parasite invasion.\",\n      \"method\": \"Genetic deletion, recombinant protein rescue, chemical inhibition and genetic knockdown of acid sphingomyelinase, invasion assays\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic deletion with rescue by exogenous EXP2 and functional analog, multiple orthogonal approaches\",\n      \"pmids\": [\"33159090\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"EXP2 forms part of a translocation intermediate complex with core PTEX components (HSP101 and PTEX150) during export of the integral membrane protein SURFIN4.1 (mini-SURFIN4.1). A processed form of Pf113 also associates with EXP2 in stable translocation intermediates at the parasite plasma membrane.\",\n      \"method\": \"Co-immunoprecipitation of translocation intermediates, structured illumination microscopy\",\n      \"journal\": \"Parasitology international\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — Co-IP of translocation intermediates, single lab, single method\",\n      \"pmids\": [\"33901679\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"EXP2 and PTEX150 form a stable subcomplex that facilitates HSP101 docking onto PTEX. This EXP2-PTEX150 subcomplex is a functional assembly unit within the translocon.\",\n      \"method\": \"Biochemical fractionation, co-immunoprecipitation, immunofluorescence showing HSP101 in parasite ER and PV\",\n      \"journal\": \"PLoS pathogens\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — Co-IP demonstrating EXP2-PTEX150 subcomplex, single lab, partially supported by localization data\",\n      \"pmids\": [\"35192672\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Postinvasion knockdown of EXP2 using the glmS ribozyme in P. berghei reduced parasite size during intrahepatic development and largely abolished expression of the mid-to-late liver-stage marker LISP2, demonstrating that EXP2 is important for intrahepatic parasite development independently of its role in invasion.\",\n      \"method\": \"glmS ribozyme-mediated conditional knockdown after hepatocyte invasion, immunofluorescence, nanoluciferase reporter assays\",\n      \"journal\": \"mBio\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — conditional knockdown with temporal separation from invasion, multiple orthogonal readouts (size, marker expression, luciferase)\",\n      \"pmids\": [\"36445080\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium berghei\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"ER sequestration (knockER) of EXP2 using inducible KDEL fusion demonstrated that EXP2 can be redistributed from the PV to the ER, establishing EXP2's secretory pathway trafficking and enabling loss-of-function studies for vacuolar EXP2.\",\n      \"method\": \"DiCre-mediated inducible KDEL ER-retrieval (knockER), fluorescence microscopy, parasite growth assays\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — novel conditional ER-sequestration approach applied to EXP2, single lab, functional consequence of redistribution established\",\n      \"pmids\": [\"37552754\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Complementation assays in EXP2 knockdown P. falciparum parasites showed that T. gondii GRA17 (a structural ortholog) cannot complement EXP2's protein export function even when supplemented with EXP2's assembly strand and linker helix. The body region of EXP2 is critical for PTEX assembly and/or EXP2 insertion efficiency into the PVM. Altering timing and abundance of EXP2 expression did not affect protein export but affected parasite viability, indicating EXP2's unique transcriptional profile enables its additional nutrient exchange role.\",\n      \"method\": \"Transgenic complementation with truncations, hybrids, and heterologous GRA17; protein export assays; parasite growth assays\",\n      \"journal\": \"Frontiers in cellular and infection microbiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vivo complementation with multiple truncation and hybrid constructs, functional export and growth readouts, single lab\",\n      \"pmids\": [\"38282616\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"FlpL/FRT-mediated disruption of exp2 in P. falciparum sporozoites did not affect sporozoite development in mosquitoes or infectivity of hepatocytes but caused 100% loss of liver parasites by day 6 post-infection, demonstrating that EXP2 is essential for intrahepatic liver-stage growth. Expression of some PEXEL proteins (LISP2, CSP but not LSA3) was reduced in exp2-FRT liver stages.\",\n      \"method\": \"FlpL/FRT conditional gene excision in sporozoites, humanized mouse liver-stage infection model, immunofluorescence of PEXEL reporter proteins\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — conditional genetic disruption in sporozoites with in vivo liver-stage readout, 100% penetrant phenotype, multiple PEXEL protein readouts\",\n      \"pmids\": [\"38968107\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"An EXP2-fluorescent reporter was used to track PVM integrity during egress, showing that the PVM ruptures at a single site and the rupture rapidly expands from that initial site, releasing merozoites. EXP2 localization allowed real-time monitoring of PVM breakdown relative to exocytosis and RBC membrane rupture.\",\n      \"method\": \"Live fluorescence imaging of EXP2-fluorescent fusion during egress, conditional mutants of PfERC\",\n      \"journal\": \"PLoS pathogens\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — EXP2 used as a PVM reporter, single lab, single method; finding is about PVM dynamics rather than a mechanistic role of EXP2 itself\",\n      \"pmids\": [\"42113900\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    }\n  ],\n  \"current_model\": \"EXP2 (PF3D7_1471100) is the membrane-spanning, pore-forming component of the PTEX translocon at the parasitophorous vacuole membrane (PVM), forming a static funnel-shaped pseudo-seven-fold-symmetric channel together with PTEX150 (as revealed by near-atomic cryo-EM), through which HSP101 threads exported proteins; EXP2 also independently functions as a nutrient-permeable channel across the PVM (dependent on EXP1 for correct localization), forms the pore via its N-terminal ~20 kDa membrane-associated region (with an intramolecular C113–C140 disulfide bond), is essential for blood-stage parasite survival, intrahepatic development, and blood-stage infection establishment, and additionally mediates hepatocyte invasion by sporozoites through its pore-forming activity inducing host membrane repair.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"EXP2 (PF3D7_1471100) is the membrane-spanning, pore-forming subunit of the Plasmodium translocon of exported proteins (PTEX) at the parasitophorous vacuole membrane (PVM), where it forms a core complex with PTEX150 and the AAA+ ATPase HSP101 that drives export of parasite proteins into the host erythrocyte [#0, #12]. Near-atomic cryo-EM of the endogenous complex shows that EXP2 and PTEX150 interdigitate into a static, funnel-shaped pseudo-seven-fold-symmetric protein-conducting channel spanning the vacuolar membrane, over which the HSP101 hexamer is tethered and undergoes conformational cycling to thread cargo [#12]; consistent with this, exported proteins arrested during translocation are trapped in complex with EXP2 at the PVM, clogging the pore and blocking export [#10, #6]. Recombinant EXP2 self-assembles into ~10\\u201312-subunit pores in lipid bilayers, and its protease-resistant, membrane-associated N-terminal ~20 kDa region (bearing a C113\\u2013C140 intramolecular disulfide bond) forms the transmembrane, pore-forming element with the C-terminus projecting into the vacuolar space [#11, #16]. Beyond protein export, EXP2 independently serves as a nutrient-permeable channel across the PVM, a function that requires EXP1 for its correct localization and organization but is separable from HSP101-dependent export [#13, #17, #18]. EXP2 is essential across the life cycle: it is required for blood-stage growth and protein export [#14], for intrahepatic liver-stage development [#7, #23, #26], and for hepatocyte invasion by sporozoites, where its pore-forming activity triggers host membrane repair that facilitates entry [#20].\",\n  \"teleology\": [\n    {\n      \"year\": 1994,\n      \"claim\": \"Establishing that EXP2 is a bona fide PVM-associated membrane protein was the prerequisite for any functional role at the host-parasite interface.\",\n      \"evidence\": \"Monoclonal antibody characterization, biochemical fractionation, and immunolocalization in P. falciparum\",\n      \"pmids\": [\"8058359\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Function of the PVM association not addressed\", \"No oligomeric or channel activity tested\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 1998,\n      \"claim\": \"Cloning showed EXP2 is a single-copy, ring-stage gene with a cleaved signal sequence and no canonical transmembrane domain, raising the question of how it inserts into the PVM.\",\n      \"evidence\": \"Gene cloning, sequencing, N-terminal microsequencing, and hydrophobicity analysis in P. falciparum\",\n      \"pmids\": [\"9574909\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Membrane-association mode inferred (amphipathic helix), not experimentally demonstrated\", \"No functional assay of the protein\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Discovery of PTEX defined EXP2 as the membrane-associated component of an ATP-powered export machine, placing it at the center of protein trafficking into the host cell.\",\n      \"evidence\": \"Co-IP, mass spectrometry, biochemical fractionation, and immunolocalization identifying the EXP2\\u2013PTEX150\\u2013HSP101 core in P. falciparum\",\n      \"pmids\": [\"19536257\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether EXP2 itself conducts cargo not yet shown\", \"Stoichiometry and structure of the channel unknown\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Tracing EXP2's biogenesis showed it is made early, stored in merozoite dense granules, and forms a stable ~600 kDa homo-oligomer at the PVM upstream of the other PTEX subunits, defining an assembly order.\",\n      \"evidence\": \"Pulse-chase, fractionation, native PAGE, and detergent separation in P. falciparum\",\n      \"pmids\": [\"22253438\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Homo-oligomer architecture not resolved\", \"Nature of EXP2\\u2013PTEX150\\u2013HSP101 coupling not defined at molecular level\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Failure to delete exp2 in P. berghei established that EXP2 is essential for blood-stage development, motivating conditional approaches.\",\n      \"evidence\": \"Repeated failed gene knockout attempts in P. berghei (two independent studies)\",\n      \"pmids\": [\"23869529\", \"24076174\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Essentiality is a negative genetic result without mechanistic cause\", \"Life-cycle stages beyond blood not addressed here\"],\n      \"attribution\": [{\"species\": \"Plasmodium berghei\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Super-resolution imaging placed protein export spatially at PVM foci containing EXP2, providing direct cellular evidence that translocation occurs where PTEX resides.\",\n      \"evidence\": \"3D-SIM, live merozoite imaging, and translocation intermediate generation in P. falciparum\",\n      \"pmids\": [\"23361006\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Does not show EXP2 physically conducting cargo\", \"Dynamics of foci formation not mechanistically explained\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Conditional deletion and tagging in P. berghei extended EXP2's essential role beyond blood stage to liver growth and transition to blood-stage infection, and revealed dynamic tubular PVM extensions consistent with pore activity.\",\n      \"evidence\": \"FLP/FRT conditional mutagenesis, mouse infection, and endogenous fluorescent tagging with CLEM in P. berghei; vesicle localization noted in P. yoelii reticulocytes\",\n      \"pmids\": [\"26347246\", \"26219962\", \"25662767\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular basis of liver-stage requirement not defined\", \"Species-divergent cytoplasmic vesicle localization in P. yoelii reticulocytes not mechanistically explained\"],\n      \"attribution\": [{\"species\": \"Plasmodium berghei\", \"strain\": \"\"}, {\"species\": \"Plasmodium yoelii\", \"strain\": \"17X\"}, {\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Trapping stalled cargo in complex with EXP2 gave the first functional proof that EXP2 is part of the translocating entity, and reconstitution showed EXP2 alone forms a defined pore.\",\n      \"evidence\": \"DHFR conditional-fold constructs with Co-IP of intermediates and growth assays; recombinant EXP2 pore reconstitution by bilayer electrophysiology, EM, SEC, and BN-PAGE in P. falciparum\",\n      \"pmids\": [\"27168322\", \"27865834\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Recombinant pore stoichiometry (~10\\u201312) differs from later cryo-EM channel; reconciliation not resolved\", \"Two-step export across PPM and PVM mechanistically defined only in outline\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Cryo-EM, conditional knockdown, and electrophysiology together defined the channel architecture and split EXP2's activities into an HSP101-dependent protein-export channel and an HSP101-independent nutrient channel.\",\n      \"evidence\": \"Near-atomic cryo-EM of endogenous PTEX; TetR-aptamer/glmS knockdown, patch-clamp, mutagenesis, and export assays; SIM of EXP2 loop extensions in P. falciparum\",\n      \"pmids\": [\"30150771\", \"30150733\", \"30439948\", \"29696751\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How the same channel switches between nutrient and protein conduction not resolved\", \"Gating and selectivity mechanisms not defined\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Biochemical topology mapping and EXP1 knockout dissected which part of EXP2 forms the pore and which partner controls its nutrient-channel function.\",\n      \"evidence\": \"Differential alkylation, protease protection, hemolysis and osmotic protection with synthetic peptide; conditional EXP1 KO with patch-clamp and export assays in P. falciparum\",\n      \"pmids\": [\"30476118\", \"31568532\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular mechanism by which EXP1 organizes EXP2 not defined\", \"Whether EXP1 acts stoichiometrically or as a chaperone unclear\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Localization studies refined EXP2's PVM organization\\u2014dependent on EXP1 and excluded from PVM/PPM contact domains\\u2014while a new role emerged in sporozoite invasion via pore-induced host membrane repair.\",\n      \"evidence\": \"CRISPR/Cpf1 EXP1 knockdown with BioID2 and EM; super-resolution imaging of contact domains; sporozoite deletion with recombinant EXP2/alpha-hemolysin/acid sphingomyelinase rescue in P. falciparum\",\n      \"pmids\": [\"31990132\", \"32732874\", \"33159090\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanistic link between EXP2 pore activity and membrane-repair signaling at hepatocyte surface incompletely defined\", \"Functional consequence of EXP2 exclusion from contact domains unknown\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Further studies defined an EXP2\\u2013PTEX150 subcomplex as the HSP101 docking platform and demonstrated a liver-stage requirement for EXP2 separable from invasion.\",\n      \"evidence\": \"Fractionation and Co-IP of the EXP2\\u2013PTEX150 subcomplex; postinvasion glmS knockdown in P. berghei with LISP2 marker and luciferase readouts\",\n      \"pmids\": [\"35192672\", \"36445080\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Subcomplex assembly demonstrated by Co-IP only\", \"Liver-stage export cargo dependence not fully enumerated\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}, {\"species\": \"Plasmodium berghei\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Complementation and conditional sporozoite disruption defined EXP2's body region as critical for PTEX assembly, showed a heterologous ortholog cannot substitute, and confirmed EXP2 is essential for intrahepatic growth after successful invasion.\",\n      \"evidence\": \"Transgenic complementation with truncations/hybrids/GRA17 and export/growth assays; FlpL/FRT sporozoite disruption with humanized-mouse liver-stage model in P. falciparum; knockER ER-sequestration\",\n      \"pmids\": [\"38282616\", \"38968107\", \"37552754\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Why GRA17 fails to complement despite structural orthology not fully explained\", \"Precise cargo set required for liver-stage growth incomplete\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How EXP2 mechanistically toggles between HSP101-driven protein translocation and HSP101-independent nutrient conduction within a single static channel, and how EXP1 physically organizes it, remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No structure of the nutrient-conducting (HSP101-free) state\", \"Gating/selectivity switch between the two modes undefined\", \"Molecular mechanism of EXP1-dependent organization of EXP2 unknown\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0015288\", \"supporting_discovery_ids\": [11, 16]},\n      {\"term_id\": \"GO:0022829\", \"supporting_discovery_ids\": [13, 17]},\n      {\"term_id\": \"GO:0015450\", \"supporting_discovery_ids\": [0, 10, 12]},\n      {\"term_id\": \"GO:0042802\", \"supporting_discovery_ids\": [3, 11]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0020005\", \"supporting_discovery_ids\": [0, 1, 2, 8]},\n      {\"term_id\": \"GO:0020003\", \"supporting_discovery_ids\": [1, 16]},\n      {\"term_id\": \"GO:0020026\", \"supporting_discovery_ids\": [3]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"GO:0065002\", \"supporting_discovery_ids\": [0, 10, 12, 14]},\n      {\"term_id\": \"GO:0015893\", \"supporting_discovery_ids\": [13, 17]},\n      {\"term_id\": \"GO:0044409\", \"supporting_discovery_ids\": [20]}\n    ],\n    \"complexes\": [\n      \"PTEX translocon core complex (EXP2\\u2013PTEX150\\u2013HSP101)\",\n      \"EXP2\\u2013PTEX150 static channel subcomplex\",\n      \"EXP2 ~600 kDa homo-oligomer\"\n    ],\n    \"partners\": [\n      \"PTEX150\",\n      \"HSP101\",\n      \"EXP1 (required for EXP2 PVM organization and nutrient-channel activity)\"\n    ],\n    \"other_free_text\": [\n      \"N-terminal ~20 kDa membrane-associated region forms the transmembrane pore; C-terminus projects into the vacuolar space [#16].\",\n      \"Intramolecular C113\\u2013C140 disulfide bond, with C201 predominantly reduced [#16].\",\n      \"Recombinant EXP2 forms ~3.5 nm pores of ~10\\u201312 subunits in lipid bilayers [#11].\",\n      \"Cryo-EM defines a static funnel-shaped pseudo-seven-fold-symmetric channel with HSP101 tethered above [#12].\",\n      \"Dual function: HSP101-dependent protein-export channel and HSP101-independent nutrient-permeable channel [#13].\",\n      \"Essential for blood-stage growth/export, intrahepatic liver-stage development, and sporozoite hepatocyte invasion via pore-induced host membrane repair [#14, #23, #26, #20].\",\n      \"Heterologous T. gondii GRA17 cannot complement EXP2's export function; the body region is critical for PTEX assembly/PVM insertion [#25].\",\n      \"Species divergence: in P. yoelii reticulocytes EXP2 also localizes to cytoplasmic vesicles, unlike exclusive PVM localization in P. falciparum mature RBCs [#9].\"\n    ]\n  }\n}","audit_flag":null,"strains":[{"strain":"Pf3D7","gene_id":"PF3D7_1471100","name":null,"product":"exported protein 2","uniprot_acc":null,"chromosome":null,"start_pos":null},{"strain":"PbANKA","gene_id":"PBANKA_1334300","name":null,"product":"exported protein 2","uniprot_acc":null,"chromosome":null,"start_pos":null},{"strain":"PkH","gene_id":"PKNH_1209900","name":null,"product":"exported protein 2, putative","uniprot_acc":null,"chromosome":null,"start_pos":null}],"gene_symbol":"EXP2","evaluation":null}