{"gene":"PF3D7_0113700","run_date":"2026-09-07T10:55:51","timeline":{"discoveries":[{"year":2016,"finding":"Recombinant PFA0660w (PF3D7_0113700) was found to exist as a monomer in solution and to significantly stimulate the ATPase activity of PfHsp70-x but not that of PfHsp70-1 or human HSPA1A, demonstrating a specific functional co-chaperone partnership with PfHsp70-x. Additionally, PFA0660w alone suppressed rhodanese aggregation in a concentration-dependent manner, demonstrating intrinsic chaperone activity.","method":"Recombinant protein expression, ATPase activity assay, protein aggregation suppression assay, protein binding studies (with and without ATP)","journal":"PloS one","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro biochemical reconstitution with multiple orthogonal assays (ATPase stimulation, aggregation suppression, binding studies) in a single study; first biochemical characterization of this protein","pmids":["26845441"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2010,"finding":"GFP- and HA-Strep-tagged PFA0660w (PF3D7_0113700) localizes to novel punctate mobile structures in the cytosol of P. falciparum-infected erythrocytes, distinct from Maurer's clefts, termed 'J-dots'. These structures are tightly associated with membranes, releasable by cholesterol-disrupting conditions, and are highly mobile, suggesting a role in trafficking parasite-encoded proteins through the host erythrocyte cytosol.","method":"Transfection with GFP/HA-Strep-tagged constructs, fluorescence microscopy, transmission electron microscopy, solubility/fractionation studies, BODIPY-ceramide labeling, cholesterol perturbation assays","journal":"Cellular microbiology","confidence":"High","confidence_rationale":"Tier 2 / Strong — direct live-cell imaging with functional consequence (membrane/cholesterol association linked to localization), replicated across multiple tagged constructs and orthogonal microscopy methods, findings cited and confirmed by subsequent studies","pmids":["20482550"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2019,"finding":"PFA0660w (PF3D7_0113700) directly binds cholesterol via a site distinct from its substrate-binding site, and forms an in vitro complex with PfHsp70-x and the cytoplasmic tail of PfEMP1 simultaneously, suggesting this chaperone pair assists PfEMP1 transport through cholesterol-containing J-dots.","method":"Recombinant protein biochemical assays, cholesterol binding assay, in vitro pulldown/complex formation assay with recombinant PfEMP1 cytoplasmic tail, co-immunoprecipitation","journal":"Scientific reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple in vitro biochemical assays identifying novel cholesterol binding and ternary complex formation; single lab, in vivo validation acknowledged as absent","pmids":["30804381"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2021,"finding":"Inactivation of PFA0660w (PFA66/PF3D7_0113700) in P. falciparum caused severe defects in knob morphology, disrupted surface presentation of PfEMP1, and abolished cytoadherence, while KAHRP was still present. Complementation showed an intact J-domain is required for wild-type phenotype rescue, and ATPase assays on recombinant protein verified a functional interaction between PFA0660w and residual host-cell HSP70, implicating human HSP70 as the relevant partner in this context.","method":"Genetic knockdown/knockout, complementation assay, transmission electron microscopy (knob morphology), cytoadherence assay, immunofluorescence (PfEMP1 surface presentation), ATPase activity assay with recombinant protein","journal":"PLoS pathogens","confidence":"High","confidence_rationale":"Tier 2 / Strong — clean loss-of-function with defined cellular phenotypes (knobs, PfEMP1 display, cytoadherence), complementation with J-domain mutant, and in vitro ATPase validation; multiple orthogonal methods","pmids":["34614006"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2019,"finding":"Computational structural modeling of PFA0660w (PF3D7_0113700) and docking with PfHsp70-x identified specific residues critical for their bipartite interaction. The peptide-binding cleft of PFA0660w was found to be larger than counterparts in yeast, humans, and C. parvum, suggesting structural differences that could be exploited for drug design.","method":"Homology modeling, molecular dynamics simulation, protein-protein docking (HADDOCK), structure verification tools","journal":"Computational biology and chemistry","confidence":"Low","confidence_rationale":"Tier 4 / Weak — purely computational prediction; no experimental structural validation or mutagenesis performed","pmids":["31430682"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2019,"finding":"Crystallographic determination of the J-domain structure of the stimulatory Hsp40 co-chaperone of PfHsp70-x was reported; the abstract describes this as the J-domain of its 'stimulatory Hsp40 cochaperone' in the context of PfHsp70-x biology. The abstract does not specify which Hsp40 gene this J-domain structure corresponds to.","method":"X-ray crystallography","journal":"FASEB journal","confidence":"Low","confidence_rationale":"Tier 1 / Weak — crystal structure reported but the abstract does not unambiguously identify the Hsp40 as PFA0660w/PF3D7_0113700 specifically; identity of the Hsp40 cannot be confirmed from abstract alone","pmids":["31690116"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]}],"current_model":"PFA0660w (PF3D7_0113700) is a monomeric, exported type II Hsp40/J-domain protein that functions both as an intrinsic chaperone (suppressing substrate aggregation) and as a specific co-chaperone that stimulates the ATPase activity of the exported P. falciparum Hsp70, PfHsp70-x, but not other Hsp70s; it binds cholesterol and localizes to highly mobile, cholesterol-rich membrane structures in the host erythrocyte cytosol called J-dots, where it forms a ternary complex with PfHsp70-x and the cytoplasmic tail of the virulence factor PfEMP1 to facilitate its trafficking; loss of PFA0660w, specifically its J-domain, abolishes knob biogenesis, PfEMP1 surface display, and cytoadherence, with functional evidence also implicating host-cell HSP70 as a relevant partner in host-cell remodeling."},"narrative":{"mechanistic_narrative":"PFA0660w (PF3D7_0113700) is an exported type II Hsp40/J-domain protein of Plasmodium falciparum that operates at the interface of host-cell remodeling, functioning both as an intrinsic chaperone and as a specific co-chaperone that drives trafficking of the virulence factor PfEMP1 to the infected erythrocyte surface [PMID:26845441, PMID:34614006]. As a monomer in solution, it suppresses substrate aggregation on its own and specifically stimulates the ATPase activity of the exported PfHsp70-x, but not PfHsp70-1 or human HSPA1A, establishing a dedicated chaperone partnership [PMID:26845441]. Within the host erythrocyte cytosol it localizes to mobile, membrane- and cholesterol-associated punctate structures termed J-dots, distinct from Maurer's clefts [PMID:20482550]; it binds cholesterol at a site separate from its substrate-binding cleft and assembles a ternary complex with PfHsp70-x and the cytoplasmic tail of PfEMP1, coupling its chaperone activity to cargo transport through these cholesterol-rich compartments [PMID:30804381]. Functionally, inactivation of PFA0660w abolishes knob biogenesis, PfEMP1 surface presentation, and cytoadherence while sparing KAHRP, and rescue requires an intact J-domain, demonstrating that its J-domain-dependent Hsp70 stimulation is essential for host-cell remodeling; in this loss-of-function context residual host-cell HSP70 was implicated as a functional partner [PMID:34614006].","teleology":[{"year":2010,"claim":"Where an exported parasite Hsp40 resides in the host cell was unknown; localizing PFA0660w to novel mobile membrane structures established a candidate trafficking platform in the erythrocyte cytosol.","evidence":"Live-cell imaging of GFP/HA-Strep-tagged PFA0660w with electron microscopy, fractionation, and cholesterol perturbation in infected erythrocytes","pmids":["20482550"],"confidence":"High","gaps":["Did not identify the trafficked cargo","Did not define the molecular basis of membrane/cholesterol association","Did not establish the co-chaperone Hsp70 partner"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2016,"claim":"Whether PFA0660w had defined chaperone biochemistry was unresolved; in vitro reconstitution showed it is a monomeric intrinsic chaperone and a specific co-chaperone that stimulates PfHsp70-x but not other Hsp70s, defining its molecular partnership.","evidence":"Recombinant protein ATPase stimulation, rhodanese aggregation-suppression, and binding assays comparing PfHsp70-x, PfHsp70-1, and human HSPA1A","pmids":["26845441"],"confidence":"High","gaps":["Did not connect ATPase stimulation to a physiological substrate","No structural basis for the specificity toward PfHsp70-x","No in-cell validation of the partnership"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2019,"claim":"How PFA0660w links chaperone activity to J-dot membranes and to a specific cargo was unknown; demonstrating direct cholesterol binding and simultaneous ternary complex formation with PfHsp70-x and the PfEMP1 cytoplasmic tail connected localization to a trafficking function.","evidence":"Recombinant cholesterol-binding assay and in vitro pulldown/co-immunoprecipitation with the PfEMP1 cytoplasmic tail and PfHsp70-x","pmids":["30804381"],"confidence":"Medium","gaps":["Ternary complex shown only in vitro; in vivo validation absent","Stoichiometry and geometry of the complex undefined","Cholesterol-binding site not mapped to specific residues experimentally"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2019,"claim":"The residue-level interface with PfHsp70-x was uncharacterized; computational modeling proposed contact residues and an enlarged peptide-binding cleft relative to other species, offering candidate drug-target features.","evidence":"Homology modeling, molecular dynamics, and HADDOCK protein-protein docking","pmids":["31430682"],"confidence":"Low","gaps":["Purely computational; no experimental structural or mutagenesis validation","Predicted interface residues untested functionally"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2019,"claim":"A crystal structure of the J-domain of a stimulatory Hsp40 co-chaperone of PfHsp70-x was reported, but the abstract does not unambiguously assign this J-domain to PFA0660w.","evidence":"X-ray crystallography of a PfHsp70-x-associated Hsp40 J-domain","pmids":["31690116"],"confidence":"Low","gaps":["Identity of the Hsp40 cannot be confirmed as PFA0660w from the available evidence","No structural data for regions beyond the J-domain"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2021,"claim":"Whether PFA0660w is functionally required for virulence-related host-cell remodeling was untested; loss-of-function with J-domain-dependent complementation established it is essential for knob biogenesis, PfEMP1 surface display, and cytoadherence.","evidence":"Genetic inactivation with complementation (J-domain mutant), electron microscopy of knobs, PfEMP1 surface immunofluorescence, cytoadherence assays, and recombinant ATPase assay with host HSP70","pmids":["34614006"],"confidence":"High","gaps":["Relative in vivo contributions of PfHsp70-x versus host HSP70 not resolved","Mechanism linking chaperone action to knob assembly not defined at molecular resolution","Whether cholesterol binding is required for the in-cell phenotype untested"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":null,"claim":"How PFA0660w mechanistically couples ATP-driven PfHsp70-x cycling, cholesterol-dependent J-dot localization, and PfEMP1 cargo handoff into knob assembly at the erythrocyte membrane remains unresolved.","evidence":"","pmids":[],"confidence":"Low","gaps":["No experimental full-length structure of PFA0660w","In-cell requirement of cholesterol binding and the ternary complex not demonstrated","Directionality and site of PfEMP1 delivery from J-dots to knobs unknown"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]}],"mechanism_profile":{"molecular_activity":[],"localization":[],"pathway":[],"complexes":["Ternary complex of PFA0660w, PfHsp70-x, and the PfEMP1 cytoplasmic tail (in vitro) [#2]"],"partners":["PFHSP70-X (SPECIFIC CO-CHAPERONE PARTNER; ATPASE STIMULATION) [#0, #2]","PFEMP1 CYTOPLASMIC TAIL (CARGO/BINDING PARTNER) [#2]","HOST-CELL HSP70 (FUNCTIONAL PARTNER IMPLICATED IN LOSS-OF-FUNCTION CONTEXT) [#3]","CHOLESTEROL (DIRECT LIGAND AT A SITE DISTINCT FROM SUBSTRATE-BINDING SITE) [#2]"],"other_free_text":["Monomeric in solution [#0]","Exported type II Hsp40/J-domain protein; intact J-domain required for function [#3]","Localizes to mobile, membrane- and cholesterol-associated J-dots distinct from Maurer's clefts [#1]","Inactivation abolishes knob biogenesis, PfEMP1 surface display, and cytoadherence while KAHRP is retained [#3]","Stimulates PfHsp70-x but not PfHsp70-1 or human HSPA1A [#0]"]}},"prefetch_data":{},"corpus_meta":[{"pmid":"17428722","id":"PMC_17428722","title":"The Hsp40 proteins of Plasmodium falciparum and other apicomplexa: regulating chaperone power in the parasite and the host.","date":"2007","source":"The international journal of biochemistry & cell biology","url":"https://pubmed.ncbi.nlm.nih.gov/17428722","citation_count":111,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["curated_ref"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"20482550","id":"PMC_20482550","title":"Parasite-encoded Hsp40 proteins define novel mobile structures in the cytosol of the P. falciparum-infected erythrocyte.","date":"2010","source":"Cellular microbiology","url":"https://pubmed.ncbi.nlm.nih.gov/20482550","citation_count":108,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["curated_ref"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"31690116","id":"PMC_31690116","title":"The Plasmodium falciparum Hsp70-x chaperone assists the heat stress response of the malaria parasite.","date":"2019","source":"FASEB journal : official publication of the Federation of American Societies for Experimental Biology","url":"https://pubmed.ncbi.nlm.nih.gov/31690116","citation_count":52,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["curated_ref"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"30804381","id":"PMC_30804381","title":"Cholesterol bound Plasmodium falciparum co-chaperone 'PFA0660w' complexes with major virulence factor 'PfEMP1' via chaperone 'PfHsp70-x'.","date":"2019","source":"Scientific reports","url":"https://pubmed.ncbi.nlm.nih.gov/30804381","citation_count":37,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["PFA0660w"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"26845441","id":"PMC_26845441","title":"The Malarial Exported PFA0660w Is an Hsp40 Co-Chaperone of PfHsp70-x.","date":"2016","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/26845441","citation_count":31,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["PFA0660w"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"33236291","id":"PMC_33236291","title":"Exported plasmodial J domain protein, PFE0055c, and PfHsp70-x form a specific co-chaperone-chaperone partnership.","date":"2020","source":"Cell stress & chaperones","url":"https://pubmed.ncbi.nlm.nih.gov/33236291","citation_count":21,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["PFA0660w"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"34614006","id":"PMC_34614006","title":"Co-chaperone involvement in knob biogenesis implicates host-derived chaperones in malaria virulence.","date":"2021","source":"PLoS pathogens","url":"https://pubmed.ncbi.nlm.nih.gov/34614006","citation_count":20,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["curated_ref"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"34569022","id":"PMC_34569022","title":"Role of the J Domain Protein Family in the Survival and Pathogenesis of Plasmodium falciparum.","date":"2021","source":"Advances in experimental medicine and biology","url":"https://pubmed.ncbi.nlm.nih.gov/34569022","citation_count":16,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["PFA0660w"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"31430682","id":"PMC_31430682","title":"Structural insights into the binding mechanism of Plasmodium falciparum exported Hsp40-Hsp70 chaperone pair.","date":"2019","source":"Computational biology and chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/31430682","citation_count":11,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["PFA0660w"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":7719,"output_tokens":2036,"usd":0.026849,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":7195,"output_tokens":3357,"usd":0.05995,"stage2_stop_reason":"end_turn"},"total_usd":0.086799,"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\": 2016,\n      \"finding\": \"Recombinant PFA0660w (PF3D7_0113700) was found to exist as a monomer in solution and to significantly stimulate the ATPase activity of PfHsp70-x but not that of PfHsp70-1 or human HSPA1A, demonstrating a specific functional co-chaperone partnership with PfHsp70-x. Additionally, PFA0660w alone suppressed rhodanese aggregation in a concentration-dependent manner, demonstrating intrinsic chaperone activity.\",\n      \"method\": \"Recombinant protein expression, ATPase activity assay, protein aggregation suppression assay, protein binding studies (with and without ATP)\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro biochemical reconstitution with multiple orthogonal assays (ATPase stimulation, aggregation suppression, binding studies) in a single study; first biochemical characterization of this protein\",\n      \"pmids\": [\"26845441\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"GFP- and HA-Strep-tagged PFA0660w (PF3D7_0113700) localizes to novel punctate mobile structures in the cytosol of P. falciparum-infected erythrocytes, distinct from Maurer's clefts, termed 'J-dots'. These structures are tightly associated with membranes, releasable by cholesterol-disrupting conditions, and are highly mobile, suggesting a role in trafficking parasite-encoded proteins through the host erythrocyte cytosol.\",\n      \"method\": \"Transfection with GFP/HA-Strep-tagged constructs, fluorescence microscopy, transmission electron microscopy, solubility/fractionation studies, BODIPY-ceramide labeling, cholesterol perturbation assays\",\n      \"journal\": \"Cellular microbiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — direct live-cell imaging with functional consequence (membrane/cholesterol association linked to localization), replicated across multiple tagged constructs and orthogonal microscopy methods, findings cited and confirmed by subsequent studies\",\n      \"pmids\": [\"20482550\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"PFA0660w (PF3D7_0113700) directly binds cholesterol via a site distinct from its substrate-binding site, and forms an in vitro complex with PfHsp70-x and the cytoplasmic tail of PfEMP1 simultaneously, suggesting this chaperone pair assists PfEMP1 transport through cholesterol-containing J-dots.\",\n      \"method\": \"Recombinant protein biochemical assays, cholesterol binding assay, in vitro pulldown/complex formation assay with recombinant PfEMP1 cytoplasmic tail, co-immunoprecipitation\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple in vitro biochemical assays identifying novel cholesterol binding and ternary complex formation; single lab, in vivo validation acknowledged as absent\",\n      \"pmids\": [\"30804381\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Inactivation of PFA0660w (PFA66/PF3D7_0113700) in P. falciparum caused severe defects in knob morphology, disrupted surface presentation of PfEMP1, and abolished cytoadherence, while KAHRP was still present. Complementation showed an intact J-domain is required for wild-type phenotype rescue, and ATPase assays on recombinant protein verified a functional interaction between PFA0660w and residual host-cell HSP70, implicating human HSP70 as the relevant partner in this context.\",\n      \"method\": \"Genetic knockdown/knockout, complementation assay, transmission electron microscopy (knob morphology), cytoadherence assay, immunofluorescence (PfEMP1 surface presentation), ATPase activity assay with recombinant protein\",\n      \"journal\": \"PLoS pathogens\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — clean loss-of-function with defined cellular phenotypes (knobs, PfEMP1 display, cytoadherence), complementation with J-domain mutant, and in vitro ATPase validation; multiple orthogonal methods\",\n      \"pmids\": [\"34614006\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Computational structural modeling of PFA0660w (PF3D7_0113700) and docking with PfHsp70-x identified specific residues critical for their bipartite interaction. The peptide-binding cleft of PFA0660w was found to be larger than counterparts in yeast, humans, and C. parvum, suggesting structural differences that could be exploited for drug design.\",\n      \"method\": \"Homology modeling, molecular dynamics simulation, protein-protein docking (HADDOCK), structure verification tools\",\n      \"journal\": \"Computational biology and chemistry\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 4 / Weak — purely computational prediction; no experimental structural validation or mutagenesis performed\",\n      \"pmids\": [\"31430682\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Crystallographic determination of the J-domain structure of the stimulatory Hsp40 co-chaperone of PfHsp70-x was reported; the abstract describes this as the J-domain of its 'stimulatory Hsp40 cochaperone' in the context of PfHsp70-x biology. The abstract does not specify which Hsp40 gene this J-domain structure corresponds to.\",\n      \"method\": \"X-ray crystallography\",\n      \"journal\": \"FASEB journal\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 1 / Weak — crystal structure reported but the abstract does not unambiguously identify the Hsp40 as PFA0660w/PF3D7_0113700 specifically; identity of the Hsp40 cannot be confirmed from abstract alone\",\n      \"pmids\": [\"31690116\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    }\n  ],\n  \"current_model\": \"PFA0660w (PF3D7_0113700) is a monomeric, exported type II Hsp40/J-domain protein that functions both as an intrinsic chaperone (suppressing substrate aggregation) and as a specific co-chaperone that stimulates the ATPase activity of the exported P. falciparum Hsp70, PfHsp70-x, but not other Hsp70s; it binds cholesterol and localizes to highly mobile, cholesterol-rich membrane structures in the host erythrocyte cytosol called J-dots, where it forms a ternary complex with PfHsp70-x and the cytoplasmic tail of the virulence factor PfEMP1 to facilitate its trafficking; loss of PFA0660w, specifically its J-domain, abolishes knob biogenesis, PfEMP1 surface display, and cytoadherence, with functional evidence also implicating host-cell HSP70 as a relevant partner in host-cell remodeling.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"PFA0660w (PF3D7_0113700) is an exported type II Hsp40/J-domain protein of Plasmodium falciparum that operates at the interface of host-cell remodeling, functioning both as an intrinsic chaperone and as a specific co-chaperone that drives trafficking of the virulence factor PfEMP1 to the infected erythrocyte surface [#0, #3]. As a monomer in solution, it suppresses substrate aggregation on its own and specifically stimulates the ATPase activity of the exported PfHsp70-x, but not PfHsp70-1 or human HSPA1A, establishing a dedicated chaperone partnership [#0]. Within the host erythrocyte cytosol it localizes to mobile, membrane- and cholesterol-associated punctate structures termed J-dots, distinct from Maurer's clefts [#1]; it binds cholesterol at a site separate from its substrate-binding cleft and assembles a ternary complex with PfHsp70-x and the cytoplasmic tail of PfEMP1, coupling its chaperone activity to cargo transport through these cholesterol-rich compartments [#2]. Functionally, inactivation of PFA0660w abolishes knob biogenesis, PfEMP1 surface presentation, and cytoadherence while sparing KAHRP, and rescue requires an intact J-domain, demonstrating that its J-domain-dependent Hsp70 stimulation is essential for host-cell remodeling; in this loss-of-function context residual host-cell HSP70 was implicated as a functional partner [#3].\",\n  \"teleology\": [\n    {\n      \"year\": 2010,\n      \"claim\": \"Where an exported parasite Hsp40 resides in the host cell was unknown; localizing PFA0660w to novel mobile membrane structures established a candidate trafficking platform in the erythrocyte cytosol.\",\n      \"evidence\": \"Live-cell imaging of GFP/HA-Strep-tagged PFA0660w with electron microscopy, fractionation, and cholesterol perturbation in infected erythrocytes\",\n      \"pmids\": [\"20482550\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not identify the trafficked cargo\", \"Did not define the molecular basis of membrane/cholesterol association\", \"Did not establish the co-chaperone Hsp70 partner\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Whether PFA0660w had defined chaperone biochemistry was unresolved; in vitro reconstitution showed it is a monomeric intrinsic chaperone and a specific co-chaperone that stimulates PfHsp70-x but not other Hsp70s, defining its molecular partnership.\",\n      \"evidence\": \"Recombinant protein ATPase stimulation, rhodanese aggregation-suppression, and binding assays comparing PfHsp70-x, PfHsp70-1, and human HSPA1A\",\n      \"pmids\": [\"26845441\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not connect ATPase stimulation to a physiological substrate\", \"No structural basis for the specificity toward PfHsp70-x\", \"No in-cell validation of the partnership\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"How PFA0660w links chaperone activity to J-dot membranes and to a specific cargo was unknown; demonstrating direct cholesterol binding and simultaneous ternary complex formation with PfHsp70-x and the PfEMP1 cytoplasmic tail connected localization to a trafficking function.\",\n      \"evidence\": \"Recombinant cholesterol-binding assay and in vitro pulldown/co-immunoprecipitation with the PfEMP1 cytoplasmic tail and PfHsp70-x\",\n      \"pmids\": [\"30804381\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Ternary complex shown only in vitro; in vivo validation absent\", \"Stoichiometry and geometry of the complex undefined\", \"Cholesterol-binding site not mapped to specific residues experimentally\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"The residue-level interface with PfHsp70-x was uncharacterized; computational modeling proposed contact residues and an enlarged peptide-binding cleft relative to other species, offering candidate drug-target features.\",\n      \"evidence\": \"Homology modeling, molecular dynamics, and HADDOCK protein-protein docking\",\n      \"pmids\": [\"31430682\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"Purely computational; no experimental structural or mutagenesis validation\", \"Predicted interface residues untested functionally\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"A crystal structure of the J-domain of a stimulatory Hsp40 co-chaperone of PfHsp70-x was reported, but the abstract does not unambiguously assign this J-domain to PFA0660w.\",\n      \"evidence\": \"X-ray crystallography of a PfHsp70-x-associated Hsp40 J-domain\",\n      \"pmids\": [\"31690116\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"Identity of the Hsp40 cannot be confirmed as PFA0660w from the available evidence\", \"No structural data for regions beyond the J-domain\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Whether PFA0660w is functionally required for virulence-related host-cell remodeling was untested; loss-of-function with J-domain-dependent complementation established it is essential for knob biogenesis, PfEMP1 surface display, and cytoadherence.\",\n      \"evidence\": \"Genetic inactivation with complementation (J-domain mutant), electron microscopy of knobs, PfEMP1 surface immunofluorescence, cytoadherence assays, and recombinant ATPase assay with host HSP70\",\n      \"pmids\": [\"34614006\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Relative in vivo contributions of PfHsp70-x versus host HSP70 not resolved\", \"Mechanism linking chaperone action to knob assembly not defined at molecular resolution\", \"Whether cholesterol binding is required for the in-cell phenotype untested\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How PFA0660w mechanistically couples ATP-driven PfHsp70-x cycling, cholesterol-dependent J-dot localization, and PfEMP1 cargo handoff into knob assembly at the erythrocyte membrane remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No experimental full-length structure of PFA0660w\", \"In-cell requirement of cholesterol binding and the ternary complex not demonstrated\", \"Directionality and site of PfEMP1 delivery from J-dots to knobs unknown\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0001671\", \"supporting_discovery_ids\": [0, 3]},\n      {\"term_id\": \"GO:0051082\", \"supporting_discovery_ids\": [0]},\n      {\"term_id\": \"GO:0031072\", \"supporting_discovery_ids\": [0, 2]},\n      {\"term_id\": \"GO:0015485\", \"supporting_discovery_ids\": [2]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0020030\", \"supporting_discovery_ids\": [1]},\n      {\"term_id\": \"GO:0020036\", \"supporting_discovery_ids\": [1, 3]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"GO:0006457\", \"supporting_discovery_ids\": [0]},\n      {\"term_id\": \"GO:0072583\", \"supporting_discovery_ids\": [1, 2]},\n      {\"term_id\": \"GO:0052572\", \"supporting_discovery_ids\": [3]}\n    ],\n    \"complexes\": [\n      \"Ternary complex of PFA0660w, PfHsp70-x, and the PfEMP1 cytoplasmic tail (in vitro) [#2]\"\n    ],\n    \"partners\": [\n      \"PfHsp70-x (specific co-chaperone partner; ATPase stimulation) [#0, #2]\",\n      \"PfEMP1 cytoplasmic tail (cargo/binding partner) [#2]\",\n      \"Host-cell HSP70 (functional partner implicated in loss-of-function context) [#3]\",\n      \"Cholesterol (direct ligand at a site distinct from substrate-binding site) [#2]\"\n    ],\n    \"other_free_text\": [\n      \"Monomeric in solution [#0]\",\n      \"Exported type II Hsp40/J-domain protein; intact J-domain required for function [#3]\",\n      \"Localizes to mobile, membrane- and cholesterol-associated J-dots distinct from Maurer's clefts [#1]\",\n      \"Inactivation abolishes knob biogenesis, PfEMP1 surface display, and cytoadherence while KAHRP is retained [#3]\",\n      \"Stimulates PfHsp70-x but not PfHsp70-1 or human HSPA1A [#0]\"\n    ]\n  }\n}","audit_flag":null,"strains":[{"strain":"Pf3D7","gene_id":"PF3D7_0113700","name":null,"product":"heat shock protein 40, type II","uniprot_acc":null,"chromosome":null,"start_pos":null}],"gene_symbol":"","evaluation":null}