{"gene":"PF3D7_0827900","run_date":"2026-09-08T12:51:27","timeline":{"discoveries":[{"year":2006,"finding":"PDI8 (PfPDI-8, PF3D7_0827900) encodes a protein with two thioredoxin domains containing CGHC active sites and a C-terminal ER retrieval signal (SEEL). Recombinant PDI8 was shown to function as a potent oxido-reductase enzyme that facilitated the disulfide-dependent conformational folding of EBA-175, a malaria vaccine candidate, in biochemical assays.","method":"Gene isolation, sequence and phylogenetic analysis, thioredoxin-domain analysis, in vitro biochemical assay of oxido-reductase activity with EBA-175 as substrate","journal":"International journal for parasitology","confidence":"Medium","confidence_rationale":"Tier 1 / Weak — in vitro enzymatic reconstitution with a defined substrate, but single lab and single study; no mutagenesis of active site reported in the abstract","pmids":["16806221"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""},{"species":"Plasmodium vivax","strain":""},{"species":"Plasmodium knowlesi","strain":""},{"species":"Plasmodium berghei","strain":""},{"species":"Plasmodium yoelii","strain":""}]},{"year":2006,"finding":"A protein corresponding to PDI8 (PF3D7_0827900, referred to as Pf52/PfPDI, mapping to MAL8P1.17) was shown by immunofluorescence to co-localize predominantly with ER-resident proteins PfBIP and PfERC, but not with the Golgi marker PfERD2, establishing its localization in the parasite endoplasmic reticulum. Recombinant PDI8 displayed oxidase/isomerase activity, reductase activity, and chaperone-like activity on denatured rhodanese, comparable to bovine and human PDI.","method":"Immunofluorescence co-localization with ER and Golgi markers; in vitro biochemical assays (oxidase/isomerase, reductase, and chaperone activity on rhodanese)","journal":"Biochimie","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct localization by IFA with multiple ER/Golgi markers combined with multiple in vitro enzymatic activity assays; single lab","pmids":["17166645"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":"3D7"}]},{"year":2000,"finding":"PDI8 (PF3D7_0827900) was isolated from P. falciparum lysate by affinity chromatography using a 1,4-bis(3-aminopropyl)piperazine antiplasmodial compound, then microsequenced and cloned, establishing that the protein bears the hallmark features of a thiol:disulfide oxidoreductase/protein disulfide isomerase and is encoded by a single-copy gene of 453 amino acids.","method":"Affinity chromatography, microsequencing, gene cloning","journal":"FEBS letters","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — direct affinity purification and sequencing establishing identity and interaction with an antiplasmodial compound; single lab, single method","pmids":["11078887"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2003,"finding":"PDI8 (PF3D7_0827900) was identified as a ferriprotoporphyrin IX (FP/heme)-binding protein from P. falciparum lysate by pull-down with FP immobilized on agarose beads followed by mass spectrometry.","method":"FP-agarose affinity pull-down, mass spectrometry identification","journal":"The Journal of biological chemistry","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single pull-down/MS identification; no functional follow-up for PDI8 specifically reported in the abstract","pmids":["12748176"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2005,"finding":"Overproduction of PDI8 (PfPDI, PF3D7_0827900) in P. pastoris increased the proportion of correctly folded Pfs25(A) isoform compared to Pfs25(B), and altered the O-linked glycosylation pattern of Pfs25(A) as detected by mass spectrometry, demonstrating a functional role for PDI8 in mediating disulfide-dependent folding and influencing O-glycosylation of a disulfide-rich substrate in a heterologous system.","method":"Heterologous overexpression in P. pastoris, biochemical purification, mass spectrometry characterization of isoforms","journal":"Journal of biotechnology","confidence":"Low","confidence_rationale":"Tier 3 / Weak — heterologous overexpression system, single lab; effects attributed to PDI8 activity but no direct enzymatic or interaction assay performed","pmids":["16274825"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2021,"finding":"PDI8 (PfPDI8, PF3D7_0827900) was identified as a substrate of the ER chaperone PfJ2 using a redox-active crosslinker (divinyl sulfone) specific for redox-active cysteines, trapping mixed disulfide intermediates between PfJ2 and PDI8 in living parasites. Conditional knockdown of PDI8 demonstrated it is required for asexual parasite growth, and the data suggest PDI8 functions in a complex with PfJ2 and other ER chaperones. Redox interactions between PDI8 and its substrates were sensitive to small-molecule inhibition.","method":"Activity-based divinyl sulfone crosslinking in intact parasites, immunoprecipitation-mass spectrometry (to identify substrates), conditional knockdown (DiCre-based), asexual growth assays, small-molecule inhibition assays","journal":"PLoS pathogens","confidence":"High","confidence_rationale":"Tier 2 / Moderate — activity-based crosslinking with IP-MS (trapping covalent intermediates) combined with conditional KD growth phenotype and small-molecule inhibition; multiple orthogonal methods in a single rigorous study","pmids":["33534803"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2009,"finding":"Protein disulfide isomerase (PDI) was identified in a microneme-enriched subcellular fraction from P. berghei ookinetes by gel LC-MS/MS and MudPIT proteomics, and micronemal localization was confirmed by immunofluorescence assay (IFA). Note: the abstract does not specify which PDI family member was identified; this finding is attributed tentatively but may reflect another PDI paralogue.","method":"Subcellular fractionation (microneme enrichment), electron microscopy confirmation, gel LC-MS/MS, MudPIT shotgun proteomics, IFA","journal":"Proteomics","confidence":"Low","confidence_rationale":"Tier 3 / Weak — localization by IFA and proteomics, but the specific PDI paralogue is not identified in the abstract, making attribution to PF3D7_0827900 uncertain","pmids":["19206106"],"is_preprint":false,"attribution":[{"species":"Plasmodium berghei","strain":""}]},{"year":2009,"finding":"The gene encoding a protein disulfide isomerase from P. chabaudi was sequenced and the protein modelled based on crystallographic structure 2B5E. A recombinant P. chabaudi PDI was produced and used to generate monoclonal antibodies, which were then used for immunolocalization of the enzyme in P. chabaudi.","method":"Gene sequencing, homology modelling, recombinant protein production, monoclonal antibody generation, immunolocalization","journal":"International journal of biological macromolecules","confidence":"Low","confidence_rationale":"Tier 3 / Weak — immunolocalization with recombinant-protein-raised antibodies in a single Plasmodium species; no functional enzymatic assay reported in the abstract; limited mechanistic depth","pmids":["19615402"],"is_preprint":false,"attribution":[{"species":"Plasmodium chabaudi","strain":""}]}],"current_model":"PDI8 (PF3D7_0827900) is an ER-resident protein disulfide isomerase in P. falciparum with two CGHC-containing thioredoxin domains and a C-terminal SEEL ER-retrieval signal; it exhibits oxidase/isomerase, reductase, and chaperone activities in vitro, can facilitate disulfide-dependent folding of substrates such as EBA-175, is trapped as a covalent mixed-disulfide intermediate with the ER chaperone PfJ2 via activity-based crosslinking in intact parasites, and is essential for asexual parasite growth, suggesting it functions as a key component of a PfJ2-containing oxidative folding network in the parasite ER whose redox activity is targetable by small molecules."},"narrative":{"mechanistic_narrative":"PDI8 (PF3D7_0827900) is an endoplasmic reticulum-resident protein disulfide isomerase of P. falciparum that catalyzes disulfide-dependent oxidative protein folding [PMID:16806221, PMID:17166645]. It carries two thioredoxin domains bearing CGHC active sites and a C-terminal SEEL ER-retrieval signal, and recombinant enzyme exhibits oxidase/isomerase, reductase, and chaperone-like activities in vitro, comparable to mammalian PDI [PMID:16806221, PMID:17166645]. Its ER localization was confirmed by co-localization with the ER markers PfBIP and PfERC but not the Golgi marker PfERD2 [PMID:17166645]. Functionally, PDI8 drives disulfide-dependent folding of parasite substrates, including the vaccine candidate EBA-175 [PMID:16806221]. In intact parasites, PDI8 is trapped as a covalent mixed-disulfide intermediate with the ER chaperone PfJ2 by activity-based crosslinking, placing it within a PfJ2-containing oxidative folding network, and conditional knockdown establishes that PDI8 is required for asexual growth; its redox interactions are sensitive to small-molecule inhibition [PMID:33534803]. PDI8 was originally purified through affinity for an antiplasmodial piperazine compound and separately identified as a heme (ferriprotoporphyrin IX)-binding protein, though the significance of heme binding has not been characterized in the available corpus [PMID:11078887, PMID:12748176].","teleology":[{"year":2000,"claim":"The question of whether P. falciparum encodes a druggable thiol:disulfide oxidoreductase was addressed by capturing the protein on an antiplasmodial small molecule, establishing PDI8 as a target-relevant enzyme.","evidence":"Affinity chromatography on a 1,4-bis(3-aminopropyl)piperazine antiplasmodial compound, microsequencing and cloning of the 453-aa single-copy gene","pmids":["11078887"],"confidence":"Medium","gaps":["Did not demonstrate catalytic activity or in-cell function","Mode of compound binding and whether it inhibits catalysis not resolved"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2003,"claim":"Whether PDI8 physically associates with heme was tested, adding a candidate ligand to its biochemistry.","evidence":"FP-agarose affinity pull-down from parasite lysate with mass spectrometry identification","pmids":["12748176"],"confidence":"Low","gaps":["Single pull-down/MS with no functional follow-up for PDI8","Functional consequence of heme binding unknown","Binding not validated with recombinant protein"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2005,"claim":"The functional consequence of PDI8 activity on a disulfide-rich substrate was probed by testing its effect on folding of a heterologous transmission-blocking antigen.","evidence":"Heterologous overexpression of PDI8 in P. pastoris with mass spectrometry analysis of Pfs25 folding isoforms and O-glycosylation","pmids":["16274825"],"confidence":"Low","gaps":["Heterologous system, not native parasite ER","No direct enzymatic or interaction assay linking effect to PDI8 catalysis","Relevance to native substrates unestablished"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2006,"claim":"The domain architecture and catalytic identity of PDI8 were defined, and its ability to fold a real parasite substrate was demonstrated, establishing it as a bona fide oxidative-folding enzyme.","evidence":"Gene isolation, thioredoxin-domain/phylogenetic analysis, and in vitro oxido-reductase assay with EBA-175 as folding substrate","pmids":["16806221"],"confidence":"Medium","gaps":["No active-site mutagenesis to confirm CGHC dependence","Single lab","In vivo relevance of EBA-175 folding not shown"],"attribution":[{"species":"Plasmodium falciparum","strain":""},{"species":"Plasmodium vivax","strain":""},{"species":"Plasmodium knowlesi","strain":""},{"species":"Plasmodium berghei","strain":""},{"species":"Plasmodium yoelii","strain":""}]},{"year":2006,"claim":"Where PDI8 acts in the cell and the breadth of its enzymatic repertoire were resolved by combining ER/Golgi co-localization with parallel activity assays.","evidence":"Immunofluorescence co-localization with PfBIP, PfERC (ER) and PfERD2 (Golgi); in vitro oxidase/isomerase, reductase, and chaperone assays on rhodanese","pmids":["17166645"],"confidence":"Medium","gaps":["Single lab","Native substrate spectrum in the ER not defined","Chaperone role in vivo not tested"],"attribution":[{"species":"Plasmodium falciparum","strain":"3D7"}]},{"year":2021,"claim":"Whether PDI8 acts within a defined ER folding network and is essential was established by trapping its covalent redox intermediates in living parasites and testing genetic requirement.","evidence":"Divinyl sulfone activity-based crosslinking with IP-MS trapping PfJ2–PDI8 mixed disulfides, DiCre conditional knockdown with asexual growth assays, and small-molecule inhibition assays","pmids":["33534803"],"confidence":"High","gaps":["Full substrate set of the PfJ2–PDI8 network not enumerated","Stoichiometry and architecture of the complex undefined","Molecular target/selectivity of the inhibitors not resolved"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":null,"claim":"It remains unresolved what the complete native substrate repertoire of PDI8 is in the parasite ER and how its heme-binding and small-molecule sensitivity connect to catalysis and druggability.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No comprehensive in-cell substrate map beyond EBA-175 and the PfJ2 interaction","Functional role of heme binding unknown","No structural model of PDI8 active-site chemistry from the corpus"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]}],"mechanism_profile":{"molecular_activity":[],"localization":[],"pathway":[],"complexes":["PfJ2-containing ER oxidative folding network [#5]"],"partners":["PFJ2 (ER CHAPERONE; COVALENT MIXED-DISULFIDE INTERMEDIATE) [#5]","EBA-175 (FOLDING SUBSTRATE) [#0]"],"other_free_text":["Two thioredoxin domains with CGHC active sites and C-terminal SEEL ER-retrieval signal; 453 aa single-copy gene [#0, #2]","Required for asexual parasite growth by conditional knockdown [#5]","Redox interactions sensitive to small-molecule inhibition; originally purified via an antiplasmodial piperazine compound [#2, #5]","A PDI localized to micronemes was reported in P. berghei ookinetes but the specific paralogue was not identified, so attribution to PF3D7_0827900 is uncertain [#6]"]}},"prefetch_data":{},"corpus_meta":[{"pmid":"16274825","id":"PMC_16274825","title":"Overproduction of Pichia pastoris or Plasmodium falciparum protein disulfide isomerase affects expression, folding and O-linked glycosylation of a malaria vaccine candidate expressed in P. pastoris.","date":"2005","source":"Journal of biotechnology","url":"https://pubmed.ncbi.nlm.nih.gov/16274825","citation_count":71,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["protein disulfide-isomerase"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"19206106","id":"PMC_19206106","title":"Characterisation of Plasmodium invasive organelles; an ookinete microneme proteome.","date":"2009","source":"Proteomics","url":"https://pubmed.ncbi.nlm.nih.gov/19206106","citation_count":64,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["curated_ref"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"12748176","id":"PMC_12748176","title":"Identification and characterization of heme-interacting proteins in the malaria parasite, Plasmodium falciparum.","date":"2003","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/12748176","citation_count":58,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["protein disulfide-isomerase"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"16806221","id":"PMC_16806221","title":"Protein disulfide isomerase assisted protein folding in malaria parasites.","date":"2006","source":"International journal for parasitology","url":"https://pubmed.ncbi.nlm.nih.gov/16806221","citation_count":39,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["protein disulfide-isomerase","PfPDI8"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"17166645","id":"PMC_17166645","title":"Biochemical properties and cellular localization of Plasmodium falciparum protein disulfide isomerase.","date":"2006","source":"Biochimie","url":"https://pubmed.ncbi.nlm.nih.gov/17166645","citation_count":29,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["protein disulfide-isomerase"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"11078887","id":"PMC_11078887","title":"Cloning of Plasmodium falciparum protein disulfide isomerase homologue by affinity purification using the antiplasmodial inhibitor 1,4-bis[3-[N-(cyclohexyl methyl)amino]propyl]piperazine.","date":"2000","source":"FEBS letters","url":"https://pubmed.ncbi.nlm.nih.gov/11078887","citation_count":25,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["protein disulfide-isomerase"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"33534803","id":"PMC_33534803","title":"A redox-active crosslinker reveals an essential and inhibitable oxidative folding network in the endoplasmic reticulum of malaria parasites.","date":"2021","source":"PLoS pathogens","url":"https://pubmed.ncbi.nlm.nih.gov/33534803","citation_count":14,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["PfPDI8"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"19294420","id":"PMC_19294420","title":"Return to sender: use of Plasmodium ER retrieval sequences to study protein transport in the infected erythrocyte and predict putative ER protein families.","date":"2009","source":"Parasitology research","url":"https://pubmed.ncbi.nlm.nih.gov/19294420","citation_count":13,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["curated_ref"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"22658767","id":"PMC_22658767","title":"Plasmodium yoelii blood-stage antigens newly identified by immunoaffinity using purified IgG antibodies from malaria-resistant mice.","date":"2012","source":"Immunobiology","url":"https://pubmed.ncbi.nlm.nih.gov/22658767","citation_count":10,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["protein disulfide-isomerase"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"32523082","id":"PMC_32523082","title":"Plasmodium falciparum immunodominant IgG epitopes in subclinical malaria.","date":"2020","source":"Scientific reports","url":"https://pubmed.ncbi.nlm.nih.gov/32523082","citation_count":8,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["PDI8","protein disulfide-isomerase"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"19615402","id":"PMC_19615402","title":"Gene sequencing, modelling and immunolocalization of the protein disulfide isomerase from Plasmodium chabaudi.","date":"2009","source":"International journal of biological macromolecules","url":"https://pubmed.ncbi.nlm.nih.gov/19615402","citation_count":7,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["protein disulfide-isomerase"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"37302957","id":"PMC_37302957","title":"Protein disulfide isomerases - a way to tackle malaria.","date":"2023","source":"Trends in parasitology","url":"https://pubmed.ncbi.nlm.nih.gov/37302957","citation_count":3,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["protein disulfide-isomerase"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"35340291","id":"PMC_35340291","title":"Activity-based Crosslinking to Identify Substrates of Thioredoxin-domain Proteinsin Malaria Parasites.","date":"2022","source":"Bio-protocol","url":"https://pubmed.ncbi.nlm.nih.gov/35340291","citation_count":3,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["protein disulfide-isomerase"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":8703,"output_tokens":2673,"usd":0.033102,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":8067,"output_tokens":3075,"usd":0.058605,"stage2_stop_reason":"end_turn"},"total_usd":0.091707,"stage1_batch_id":"msgbatch_01DisAaTypwmC8QwdMBuePHo","stage2_batch_id":"msgbatch_0184zxZTqxiEfdYYfPMfkqjb","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2006,\n      \"finding\": \"PDI8 (PfPDI-8, PF3D7_0827900) encodes a protein with two thioredoxin domains containing CGHC active sites and a C-terminal ER retrieval signal (SEEL). Recombinant PDI8 was shown to function as a potent oxido-reductase enzyme that facilitated the disulfide-dependent conformational folding of EBA-175, a malaria vaccine candidate, in biochemical assays.\",\n      \"method\": \"Gene isolation, sequence and phylogenetic analysis, thioredoxin-domain analysis, in vitro biochemical assay of oxido-reductase activity with EBA-175 as substrate\",\n      \"journal\": \"International journal for parasitology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Weak — in vitro enzymatic reconstitution with a defined substrate, but single lab and single study; no mutagenesis of active site reported in the abstract\",\n      \"pmids\": [\"16806221\"],\n      \"is_preprint\": false,\n      \"attribution\": [\n        {\"species\": \"Plasmodium falciparum\", \"strain\": \"\"},\n        {\"species\": \"Plasmodium vivax\", \"strain\": \"\"},\n        {\"species\": \"Plasmodium knowlesi\", \"strain\": \"\"},\n        {\"species\": \"Plasmodium berghei\", \"strain\": \"\"},\n        {\"species\": \"Plasmodium yoelii\", \"strain\": \"\"}\n      ]\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"A protein corresponding to PDI8 (PF3D7_0827900, referred to as Pf52/PfPDI, mapping to MAL8P1.17) was shown by immunofluorescence to co-localize predominantly with ER-resident proteins PfBIP and PfERC, but not with the Golgi marker PfERD2, establishing its localization in the parasite endoplasmic reticulum. Recombinant PDI8 displayed oxidase/isomerase activity, reductase activity, and chaperone-like activity on denatured rhodanese, comparable to bovine and human PDI.\",\n      \"method\": \"Immunofluorescence co-localization with ER and Golgi markers; in vitro biochemical assays (oxidase/isomerase, reductase, and chaperone activity on rhodanese)\",\n      \"journal\": \"Biochimie\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct localization by IFA with multiple ER/Golgi markers combined with multiple in vitro enzymatic activity assays; single lab\",\n      \"pmids\": [\"17166645\"],\n      \"is_preprint\": false,\n      \"attribution\": [\n        {\"species\": \"Plasmodium falciparum\", \"strain\": \"3D7\"}\n      ]\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"PDI8 (PF3D7_0827900) was isolated from P. falciparum lysate by affinity chromatography using a 1,4-bis(3-aminopropyl)piperazine antiplasmodial compound, then microsequenced and cloned, establishing that the protein bears the hallmark features of a thiol:disulfide oxidoreductase/protein disulfide isomerase and is encoded by a single-copy gene of 453 amino acids.\",\n      \"method\": \"Affinity chromatography, microsequencing, gene cloning\",\n      \"journal\": \"FEBS letters\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — direct affinity purification and sequencing establishing identity and interaction with an antiplasmodial compound; single lab, single method\",\n      \"pmids\": [\"11078887\"],\n      \"is_preprint\": false,\n      \"attribution\": [\n        {\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}\n      ]\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"PDI8 (PF3D7_0827900) was identified as a ferriprotoporphyrin IX (FP/heme)-binding protein from P. falciparum lysate by pull-down with FP immobilized on agarose beads followed by mass spectrometry.\",\n      \"method\": \"FP-agarose affinity pull-down, mass spectrometry identification\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single pull-down/MS identification; no functional follow-up for PDI8 specifically reported in the abstract\",\n      \"pmids\": [\"12748176\"],\n      \"is_preprint\": false,\n      \"attribution\": [\n        {\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}\n      ]\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Overproduction of PDI8 (PfPDI, PF3D7_0827900) in P. pastoris increased the proportion of correctly folded Pfs25(A) isoform compared to Pfs25(B), and altered the O-linked glycosylation pattern of Pfs25(A) as detected by mass spectrometry, demonstrating a functional role for PDI8 in mediating disulfide-dependent folding and influencing O-glycosylation of a disulfide-rich substrate in a heterologous system.\",\n      \"method\": \"Heterologous overexpression in P. pastoris, biochemical purification, mass spectrometry characterization of isoforms\",\n      \"journal\": \"Journal of biotechnology\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — heterologous overexpression system, single lab; effects attributed to PDI8 activity but no direct enzymatic or interaction assay performed\",\n      \"pmids\": [\"16274825\"],\n      \"is_preprint\": false,\n      \"attribution\": [\n        {\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}\n      ]\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"PDI8 (PfPDI8, PF3D7_0827900) was identified as a substrate of the ER chaperone PfJ2 using a redox-active crosslinker (divinyl sulfone) specific for redox-active cysteines, trapping mixed disulfide intermediates between PfJ2 and PDI8 in living parasites. Conditional knockdown of PDI8 demonstrated it is required for asexual parasite growth, and the data suggest PDI8 functions in a complex with PfJ2 and other ER chaperones. Redox interactions between PDI8 and its substrates were sensitive to small-molecule inhibition.\",\n      \"method\": \"Activity-based divinyl sulfone crosslinking in intact parasites, immunoprecipitation-mass spectrometry (to identify substrates), conditional knockdown (DiCre-based), asexual growth assays, small-molecule inhibition assays\",\n      \"journal\": \"PLoS pathogens\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — activity-based crosslinking with IP-MS (trapping covalent intermediates) combined with conditional KD growth phenotype and small-molecule inhibition; multiple orthogonal methods in a single rigorous study\",\n      \"pmids\": [\"33534803\"],\n      \"is_preprint\": false,\n      \"attribution\": [\n        {\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}\n      ]\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Protein disulfide isomerase (PDI) was identified in a microneme-enriched subcellular fraction from P. berghei ookinetes by gel LC-MS/MS and MudPIT proteomics, and micronemal localization was confirmed by immunofluorescence assay (IFA). Note: the abstract does not specify which PDI family member was identified; this finding is attributed tentatively but may reflect another PDI paralogue.\",\n      \"method\": \"Subcellular fractionation (microneme enrichment), electron microscopy confirmation, gel LC-MS/MS, MudPIT shotgun proteomics, IFA\",\n      \"journal\": \"Proteomics\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — localization by IFA and proteomics, but the specific PDI paralogue is not identified in the abstract, making attribution to PF3D7_0827900 uncertain\",\n      \"pmids\": [\"19206106\"],\n      \"is_preprint\": false,\n      \"attribution\": [\n        {\"species\": \"Plasmodium berghei\", \"strain\": \"\"}\n      ]\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"The gene encoding a protein disulfide isomerase from P. chabaudi was sequenced and the protein modelled based on crystallographic structure 2B5E. A recombinant P. chabaudi PDI was produced and used to generate monoclonal antibodies, which were then used for immunolocalization of the enzyme in P. chabaudi.\",\n      \"method\": \"Gene sequencing, homology modelling, recombinant protein production, monoclonal antibody generation, immunolocalization\",\n      \"journal\": \"International journal of biological macromolecules\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — immunolocalization with recombinant-protein-raised antibodies in a single Plasmodium species; no functional enzymatic assay reported in the abstract; limited mechanistic depth\",\n      \"pmids\": [\"19615402\"],\n      \"is_preprint\": false,\n      \"attribution\": [\n        {\"species\": \"Plasmodium chabaudi\", \"strain\": \"\"}\n      ]\n    }\n  ],\n  \"current_model\": \"PDI8 (PF3D7_0827900) is an ER-resident protein disulfide isomerase in P. falciparum with two CGHC-containing thioredoxin domains and a C-terminal SEEL ER-retrieval signal; it exhibits oxidase/isomerase, reductase, and chaperone activities in vitro, can facilitate disulfide-dependent folding of substrates such as EBA-175, is trapped as a covalent mixed-disulfide intermediate with the ER chaperone PfJ2 via activity-based crosslinking in intact parasites, and is essential for asexual parasite growth, suggesting it functions as a key component of a PfJ2-containing oxidative folding network in the parasite ER whose redox activity is targetable by small molecules.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"PDI8 (PF3D7_0827900) is an endoplasmic reticulum-resident protein disulfide isomerase of P. falciparum that catalyzes disulfide-dependent oxidative protein folding [#0, #1]. It carries two thioredoxin domains bearing CGHC active sites and a C-terminal SEEL ER-retrieval signal, and recombinant enzyme exhibits oxidase/isomerase, reductase, and chaperone-like activities in vitro, comparable to mammalian PDI [#0, #1]. Its ER localization was confirmed by co-localization with the ER markers PfBIP and PfERC but not the Golgi marker PfERD2 [#1]. Functionally, PDI8 drives disulfide-dependent folding of parasite substrates, including the vaccine candidate EBA-175 [#0]. In intact parasites, PDI8 is trapped as a covalent mixed-disulfide intermediate with the ER chaperone PfJ2 by activity-based crosslinking, placing it within a PfJ2-containing oxidative folding network, and conditional knockdown establishes that PDI8 is required for asexual growth; its redox interactions are sensitive to small-molecule inhibition [#5]. PDI8 was originally purified through affinity for an antiplasmodial piperazine compound and separately identified as a heme (ferriprotoporphyrin IX)-binding protein, though the significance of heme binding has not been characterized in the available corpus [#2, #3].\",\n  \"teleology\": [\n    {\n      \"year\": 2000,\n      \"claim\": \"The question of whether P. falciparum encodes a druggable thiol:disulfide oxidoreductase was addressed by capturing the protein on an antiplasmodial small molecule, establishing PDI8 as a target-relevant enzyme.\",\n      \"evidence\": \"Affinity chromatography on a 1,4-bis(3-aminopropyl)piperazine antiplasmodial compound, microsequencing and cloning of the 453-aa single-copy gene\",\n      \"pmids\": [\"11078887\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Did not demonstrate catalytic activity or in-cell function\", \"Mode of compound binding and whether it inhibits catalysis not resolved\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Whether PDI8 physically associates with heme was tested, adding a candidate ligand to its biochemistry.\",\n      \"evidence\": \"FP-agarose affinity pull-down from parasite lysate with mass spectrometry identification\",\n      \"pmids\": [\"12748176\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"Single pull-down/MS with no functional follow-up for PDI8\", \"Functional consequence of heme binding unknown\", \"Binding not validated with recombinant protein\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"The functional consequence of PDI8 activity on a disulfide-rich substrate was probed by testing its effect on folding of a heterologous transmission-blocking antigen.\",\n      \"evidence\": \"Heterologous overexpression of PDI8 in P. pastoris with mass spectrometry analysis of Pfs25 folding isoforms and O-glycosylation\",\n      \"pmids\": [\"16274825\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"Heterologous system, not native parasite ER\", \"No direct enzymatic or interaction assay linking effect to PDI8 catalysis\", \"Relevance to native substrates unestablished\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"The domain architecture and catalytic identity of PDI8 were defined, and its ability to fold a real parasite substrate was demonstrated, establishing it as a bona fide oxidative-folding enzyme.\",\n      \"evidence\": \"Gene isolation, thioredoxin-domain/phylogenetic analysis, and in vitro oxido-reductase assay with EBA-175 as folding substrate\",\n      \"pmids\": [\"16806221\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No active-site mutagenesis to confirm CGHC dependence\", \"Single lab\", \"In vivo relevance of EBA-175 folding not shown\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}, {\"species\": \"Plasmodium vivax\", \"strain\": \"\"}, {\"species\": \"Plasmodium knowlesi\", \"strain\": \"\"}, {\"species\": \"Plasmodium berghei\", \"strain\": \"\"}, {\"species\": \"Plasmodium yoelii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Where PDI8 acts in the cell and the breadth of its enzymatic repertoire were resolved by combining ER/Golgi co-localization with parallel activity assays.\",\n      \"evidence\": \"Immunofluorescence co-localization with PfBIP, PfERC (ER) and PfERD2 (Golgi); in vitro oxidase/isomerase, reductase, and chaperone assays on rhodanese\",\n      \"pmids\": [\"17166645\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single lab\", \"Native substrate spectrum in the ER not defined\", \"Chaperone role in vivo not tested\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"3D7\"}]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Whether PDI8 acts within a defined ER folding network and is essential was established by trapping its covalent redox intermediates in living parasites and testing genetic requirement.\",\n      \"evidence\": \"Divinyl sulfone activity-based crosslinking with IP-MS trapping PfJ2–PDI8 mixed disulfides, DiCre conditional knockdown with asexual growth assays, and small-molecule inhibition assays\",\n      \"pmids\": [\"33534803\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Full substrate set of the PfJ2–PDI8 network not enumerated\", \"Stoichiometry and architecture of the complex undefined\", \"Molecular target/selectivity of the inhibitors not resolved\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"It remains unresolved what the complete native substrate repertoire of PDI8 is in the parasite ER and how its heme-binding and small-molecule sensitivity connect to catalysis and druggability.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No comprehensive in-cell substrate map beyond EBA-175 and the PfJ2 interaction\", \"Functional role of heme binding unknown\", \"No structural model of PDI8 active-site chemistry from the corpus\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0003756\", \"supporting_discovery_ids\": [0, 1, 2]},\n      {\"term_id\": \"GO:0015035\", \"supporting_discovery_ids\": [1]},\n      {\"term_id\": \"GO:0051082\", \"supporting_discovery_ids\": [1]},\n      {\"term_id\": \"GO:0020037\", \"supporting_discovery_ids\": [3]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005788\", \"supporting_discovery_ids\": [0, 1]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"GO:0006457\", \"supporting_discovery_ids\": [0, 1, 4]},\n      {\"term_id\": \"GO:0034976\", \"supporting_discovery_ids\": [5]}\n    ],\n    \"complexes\": [\"PfJ2-containing ER oxidative folding network [#5]\"],\n    \"partners\": [\"PfJ2 (ER chaperone; covalent mixed-disulfide intermediate) [#5]\", \"EBA-175 (folding substrate) [#0]\"],\n    \"other_free_text\": [\n      \"Two thioredoxin domains with CGHC active sites and C-terminal SEEL ER-retrieval signal; 453 aa single-copy gene [#0, #2]\",\n      \"Required for asexual parasite growth by conditional knockdown [#5]\",\n      \"Redox interactions sensitive to small-molecule inhibition; originally purified via an antiplasmodial piperazine compound [#2, #5]\",\n      \"A PDI localized to micronemes was reported in P. berghei ookinetes but the specific paralogue was not identified, so attribution to PF3D7_0827900 is uncertain [#6]\"\n    ]\n  }\n}","audit_flag":null,"strains":[{"strain":"Pf3D7","gene_id":"PF3D7_0827900","name":null,"product":"protein disulfide-isomerase","uniprot_acc":null,"chromosome":null,"start_pos":null},{"strain":"PbANKA","gene_id":"PBANKA_0702800","name":null,"product":"protein disulfide-isomerase, putative","uniprot_acc":null,"chromosome":null,"start_pos":null},{"strain":"PkH","gene_id":"PKNH_1322000","name":null,"product":"protein disulfide-isomerase, putative","uniprot_acc":null,"chromosome":null,"start_pos":null}],"gene_symbol":"PDI8","evaluation":null}