{"gene":"PF3D7_1345100","run_date":"2026-09-08T14:19:06","timeline":{"discoveries":[{"year":2009,"finding":"TRX2 (PF3D7_1345100) was identified as a component of the PTEX (Plasmodium translocon of exported proteins) complex, which is located in the parasitophorous vacuole membrane and is ATP-powered, functioning to export parasite proteins into the host erythrocyte cytosol.","method":"Biochemical isolation and identification of the PTEX complex from P. falciparum","journal":"Nature","confidence":"High","confidence_rationale":"Tier 2 / Strong — original complex identification replicated across multiple subsequent independent studies using Co-IP and biochemical fractionation","pmids":["19536257"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2011,"finding":"TRX2 adopts a canonical thioredoxin fold with significant structural differences in its N-terminus, and localizes to the parasitophorous vacuolar membrane (PVM) as shown by confocal microscopy.","method":"Crystal structure determination and confocal localization using GFP fusions","journal":"Scientific reports","confidence":"Medium","confidence_rationale":"Tier 1-2 / Weak — crystal structure plus confocal localization in a single lab study","pmids":["22355694"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2013,"finding":"TRX2 is a genuine PTEX member; TRX2 knockout parasites in P. berghei display reduced growth rates in vivo and in vitro and reduced capacity to cause severe disease in a cerebral malaria model, indicating TRX2 is not essential for parasite survival but helps optimize PTEX activity.","method":"Genetic deletion (knockout) in P. berghei with in vivo and in vitro growth assays and cerebral malaria phenotype analysis","journal":"Molecular microbiology","confidence":"High","confidence_rationale":"Tier 2 / Strong — clean genetic knockout with defined cellular and in vivo phenotypes, replicated in a second independent study (PMID:24076174)","pmids":["23869529"],"is_preprint":false,"attribution":[{"species":"Plasmodium berghei","strain":""}]},{"year":2013,"finding":"TRX2 knockout in P. berghei results in reduced blood-stage growth, though the deficit is less severe than for PTEX88 knockouts; endogenous tagging revealed TRX2::tag resides in distinct punctate organelles of unknown identity in blood stage parasites.","method":"Genetic deletion and endogenous tagging with flow cytometry-assisted intravital competition assay in P. berghei","journal":"Molecular and biochemical parasitology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — independent replication of TRX2 knockout growth phenotype, with direct localization by endogenous tagging in a single lab","pmids":["24076174"],"is_preprint":false,"attribution":[{"species":"Plasmodium berghei","strain":""}]},{"year":2014,"finding":"Parasites lacking TRX2 show greatly reduced trafficking of all classes of exported proteins (PEXEL and PEXEL-negative) beyond the double-membrane barrier, including the major virulence factor PfEMP1, establishing TRX2's role in protein translocation through PTEX.","method":"Analysis of a TRX2 knockout P. falciparum line combined with protein export assays","journal":"Nature","confidence":"High","confidence_rationale":"Tier 2 / Strong — direct loss-of-function with defined molecular phenotype (export of multiple protein classes), reported in a high-impact study with multiple orthogonal assays","pmids":["25043043"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2014,"finding":"TRX2 crystal structure solved at 2.2-Å resolution reveals a canonical thioredoxin fold; SAXS and size exclusion chromatography demonstrate TRX2 is monomeric in solution; a non-conserved flexible N-terminal extension precedes the thioredoxin fold. The protein samples both redox catalytic states within the asymmetric unit, confirming its function as a protein disulfide reductase.","method":"X-ray crystallography (2.2 Å), size exclusion chromatography, and small-angle X-ray scattering (SAXS)","journal":"Biochemical and biophysical research communications","confidence":"High","confidence_rationale":"Tier 1 / Moderate — crystal structure with SAXS validation, multiple orthogonal biophysical methods in one study","pmids":["25475729"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2015,"finding":"TRX2-deficient P. berghei parasites show reduced sequestration to pulmonary, adipose, and brain tissue vasculature, yet remain virulent; this indicates TRX2 contributes to efficient tissue sequestration in vivo.","method":"Genetic deletion of TRX2 in P. berghei with in vivo tissue sequestration and virulence assays","journal":"Eukaryotic cell","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — clean knockout with defined in vivo phenotype, single lab but corroborates prior TRX2 knockout findings","pmids":["25820521"],"is_preprint":false,"attribution":[{"species":"Plasmodium berghei","strain":""}]},{"year":2006,"finding":"The mitochondrial thioredoxin of P. falciparum (PfTrx2, the mitochondrial isoform characterized in this study, distinct from the PTEX component TRX2/PF3D7_1345100) acts as a reducing partner for the mitochondrial 2-Cys peroxiredoxin with a KM of 11.6 µM, much lower than for the cytosolic thioredoxin (PfTrx1, KM 130.4 µM), and both proteins localize to the mitochondrion by GFP fusion.","method":"Recombinant protein kinetic characterization (enzyme assay), GFP fusion localization in P. falciparum erythrocytic stages, and X-ray crystallography of the peroxiredoxin","journal":"Molecular microbiology","confidence":"Low","confidence_rationale":"Tier 2 / Weak — NOTE: This paper uses 'PfTrx2' to refer to a mitochondrial thioredoxin; it is unclear whether this corresponds exactly to PF3D7_1345100 (PTEX TRX2) or a different locus; single lab, may be a different family member","pmids":["16879648"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2010,"finding":"Subcellular localization mapping of P. falciparum redox proteins demonstrated compartmentation of thioredoxin-like proteins; TRX2 (as part of the thioredoxin family survey) was shown to have distinct subcellular targeting, and thioredoxin reductase achieves dual localization via alternative translation initiation.","method":"Systematic subcellular localization study using fluorescent protein fusions in P. falciparum","journal":"PLoS pathogens","confidence":"Low","confidence_rationale":"Tier 3 / Weak — pan-redox-protein survey; TRX2-specific mechanistic detail is minimal; single lab","pmids":["21203490"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2017,"finding":"TRX2 is a poor substrate for thioredoxin reductase and lacks access to thioredoxin reductase; nevertheless, TRX2 can be reduced by the glutathione system (glutaredoxin/glutathione), demonstrating functional cross-talk between the glutathione and thioredoxin antioxidant systems in P. falciparum.","method":"In vitro biochemical reduction assays with recombinant proteins measuring cross-reactivity between glutathione and thioredoxin systems","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 1 / Weak — in vitro biochemical assay establishing enzymatic substrate relationship, single lab","pmids":["28479253"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]}],"current_model":"TRX2 (PF3D7_1345100) is a monomeric protein disulfide reductase with a canonical thioredoxin fold (crystal structure resolved at 2.2 Å) that localizes to the parasitophorous vacuolar membrane as a non-essential but functionally important component of the PTEX complex; loss of TRX2 impairs export of all classes of parasite proteins into the host erythrocyte, reduces blood-stage growth, diminishes tissue sequestration in vivo, and reduces virulence in cerebral malaria models, while its enzymatic activity can be sustained by the glutathione system when thioredoxin reductase access is limiting."},"narrative":{"mechanistic_narrative":"TRX2 (PF3D7_1345100) is a component of PTEX, the ATP-powered translocon in the parasitophorous vacuolar membrane (PVM) that exports parasite proteins into the host erythrocyte cytosol [PMID:19536257, PMID:22355694]. It adopts a canonical thioredoxin fold with a non-conserved flexible N-terminal extension, is monomeric in solution, and samples both redox catalytic states in the crystal, confirming its identity as a protein disulfide reductase [PMID:25475729]. Functionally, TRX2 is non-essential but optimizes translocation: parasites lacking TRX2 show reduced trafficking of all classes of exported proteins beyond the double-membrane barrier, including the virulence factor PfEMP1 [PMID:25043043], and in P. berghei TRX2 deletion causes reduced blood-stage growth, diminished tissue sequestration, and attenuated severe disease in a cerebral malaria model [PMID:23869529, PMID:25820521]. TRX2 is a poor substrate for thioredoxin reductase, but its reducing activity can be sustained by the glutathione/glutaredoxin system, linking it to the parasite's broader antioxidant network [PMID:28479253]. The precise catalytic function TRX2 performs within the PTEX translocation cycle has not been resolved in the available corpus.","teleology":[{"year":2009,"claim":"Establishing that TRX2 is a bona fide subunit of an export machine answered where and in what context the protein operates, placing it in the protein-export pathway rather than a free cytosolic redox pool.","evidence":"Biochemical isolation and identification of the PTEX complex from P. falciparum","pmids":["19536257"],"confidence":"High","gaps":["Does not define TRX2's specific molecular contribution to translocation","Stoichiometry and assembly order within PTEX unresolved"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2011,"claim":"Solving the fold and mapping subcellular location established TRX2 as a thioredoxin-fold protein resident at the PVM, consistent with its PTEX membership.","evidence":"Crystal structure determination and confocal localization of GFP fusions in P. falciparum","pmids":["22355694"],"confidence":"Medium","gaps":["Functional consequence of the divergent N-terminus unknown","Localization based on GFP fusion in a single study"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2013,"claim":"Genetic deletion answered whether TRX2 is required for survival, showing it is dispensable but needed to optimize growth and full virulence.","evidence":"TRX2 knockout in P. berghei with in vivo/in vitro growth and cerebral malaria phenotype assays, independently replicated with endogenous tagging","pmids":["23869529","24076174"],"confidence":"High","gaps":["Endogenous tag localized to punctate organelles of unknown identity","Molecular basis of the growth deficit not defined"],"attribution":[{"species":"Plasmodium berghei","strain":""}]},{"year":2014,"claim":"Loss-of-function export assays established that TRX2 is required for efficient translocation of all classes of exported proteins, defining its role at the mechanistic level of the export barrier.","evidence":"TRX2 knockout P. falciparum line combined with protein export assays for PEXEL and PEXEL-negative cargo including PfEMP1","pmids":["25043043"],"confidence":"High","gaps":["Whether TRX2 acts as a disulfide reductase on cargo or on the translocon during export is not resolved","No direct substrate of TRX2 identified during translocation"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2014,"claim":"High-resolution structural and biophysical analysis confirmed TRX2 is a monomeric protein disulfide reductase, providing the enzymatic identity underlying its export role.","evidence":"X-ray crystallography (2.2 Å), size-exclusion chromatography, and SAXS on recombinant TRX2","pmids":["25475729"],"confidence":"High","gaps":["Physiological substrate of the reductase activity not identified","Structure does not reveal how TRX2 engages the PTEX translocon"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2015,"claim":"In vivo sequestration assays showed TRX2 contributes to efficient tissue sequestration, connecting its export function to host-interaction phenotypes.","evidence":"TRX2 deletion in P. berghei with tissue sequestration and virulence assays","pmids":["25820521"],"confidence":"Medium","gaps":["Reduced sequestration not mechanistically linked to a specific exported adhesin in this system","Parasites remained virulent, indicating partial redundancy"],"attribution":[{"species":"Plasmodium berghei","strain":""}]},{"year":2017,"claim":"Biochemical reduction assays answered how TRX2 is kept reduced, showing it is a poor thioredoxin-reductase substrate but can be recycled by the glutathione system, revealing cross-talk between antioxidant systems.","evidence":"In vitro reduction assays with recombinant proteins measuring glutathione/thioredoxin system cross-reactivity in P. falciparum","pmids":["28479253"],"confidence":"Medium","gaps":["Whether glutathione-dependent recycling operates at the PVM in vivo is untested","Physiological electron donor during export not established"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":null,"claim":"The specific disulfide-bond substrate and catalytic step TRX2 performs within the PTEX translocation cycle remain unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No cargo or translocon substrate of TRX2's reductase activity identified during export","Mechanistic link between reductase activity and translocation efficiency unproven"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]}],"mechanism_profile":{"molecular_activity":[],"localization":[],"pathway":[],"complexes":["PTEX (Plasmodium translocon of exported proteins)"],"partners":[],"other_free_text":["Non-essential in P. berghei; knockout reduces blood-stage growth, tissue sequestration, and severe-disease capacity [#2, #3, #6]","Required for efficient export of PEXEL and PEXEL-negative proteins including PfEMP1 in P. falciparum [#4]","Monomeric with canonical thioredoxin fold and divergent flexible N-terminal extension [#5, #1]","Poor thioredoxin reductase substrate; reducible by the glutathione/glutaredoxin system [#9]","Idx 7 describes a mitochondrial thioredoxin (referred to as PfTrx2) that may be a distinct locus from PF3D7_1345100 and is excluded from the TRX2 mechanistic claims"]}},"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":["TRX2","thioredoxin 2"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"25043043","id":"PMC_25043043","title":"PTEX is an essential nexus for protein export in malaria parasites.","date":"2014","source":"Nature","url":"https://pubmed.ncbi.nlm.nih.gov/25043043","citation_count":207,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["TRX2"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"21203490","id":"PMC_21203490","title":"Compartmentation of redox metabolism in malaria parasites.","date":"2010","source":"PLoS pathogens","url":"https://pubmed.ncbi.nlm.nih.gov/21203490","citation_count":122,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["curated_ref"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"23869529","id":"PMC_23869529","title":"The Plasmodium translocon of exported proteins (PTEX) component thioredoxin-2 is important for maintaining normal blood-stage growth.","date":"2013","source":"Molecular microbiology","url":"https://pubmed.ncbi.nlm.nih.gov/23869529","citation_count":72,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["TRX2","thioredoxin 2"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"16910770","id":"PMC_16910770","title":"Thioredoxin networks in the malarial parasite Plasmodium falciparum.","date":"2006","source":"Antioxidants & redox signaling","url":"https://pubmed.ncbi.nlm.nih.gov/16910770","citation_count":72,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["curated_ref"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"24076174","id":"PMC_24076174","title":"Two putative protein export regulators promote Plasmodium blood stage development in vivo.","date":"2013","source":"Molecular and biochemical parasitology","url":"https://pubmed.ncbi.nlm.nih.gov/24076174","citation_count":66,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["TRX2","thioredoxin 2"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"16879648","id":"PMC_16879648","title":"Structural and biochemical characterization of a mitochondrial peroxiredoxin from Plasmodium falciparum.","date":"2006","source":"Molecular microbiology","url":"https://pubmed.ncbi.nlm.nih.gov/16879648","citation_count":44,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["TRX2","PfTRX2"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"25820521","id":"PMC_25820521","title":"In Vivo Function of PTEX88 in Malaria Parasite Sequestration and Virulence.","date":"2015","source":"Eukaryotic cell","url":"https://pubmed.ncbi.nlm.nih.gov/25820521","citation_count":32,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["TRX2","thioredoxin 2"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"22355694","id":"PMC_22355694","title":"Structural insights into thioredoxin-2: a component of malaria parasite protein secretion machinery.","date":"2011","source":"Scientific reports","url":"https://pubmed.ncbi.nlm.nih.gov/22355694","citation_count":24,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["thioredoxin 2","PfTRX2"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"27865834","id":"PMC_27865834","title":"Expression and characterization of the Plasmodium translocon of the exported proteins component EXP2.","date":"2016","source":"Biochemical and biophysical research communications","url":"https://pubmed.ncbi.nlm.nih.gov/27865834","citation_count":23,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["TRX2"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"28479253","id":"PMC_28479253","title":"Glutathione and thioredoxin systems of the malaria parasite Plasmodium falciparum: Partners in crime?","date":"2017","source":"Biochemical and biophysical research communications","url":"https://pubmed.ncbi.nlm.nih.gov/28479253","citation_count":16,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["thioredoxin 2"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"25475729","id":"PMC_25475729","title":"Crystal structure and solution characterization of the thioredoxin-2 from Plasmodium falciparum, a constituent of an essential parasitic protein export complex.","date":"2014","source":"Biochemical and biophysical research communications","url":"https://pubmed.ncbi.nlm.nih.gov/25475729","citation_count":15,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["TRX2","thioredoxin 2"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"26222913","id":"PMC_26222913","title":"Global expression profiling reveals shared and distinct transcript signatures in arrested act2(-) and CDPK4(-) Plasmodium berghei gametocytes.","date":"2015","source":"Molecular and biochemical parasitology","url":"https://pubmed.ncbi.nlm.nih.gov/26222913","citation_count":3,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["TRX2","thioredoxin 2"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":8817,"output_tokens":2659,"usd":0.033168,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":8151,"output_tokens":2854,"usd":0.056052,"stage2_stop_reason":"end_turn"},"total_usd":0.08922,"stage1_batch_id":"msgbatch_011BPjN2BL33F8cJXD1r7V7T","stage2_batch_id":"msgbatch_01Qwg6vP7qxkpL6Gsc7tajsb","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2009,\n      \"finding\": \"TRX2 (PF3D7_1345100) was identified as a component of the PTEX (Plasmodium translocon of exported proteins) complex, which is located in the parasitophorous vacuole membrane and is ATP-powered, functioning to export parasite proteins into the host erythrocyte cytosol.\",\n      \"method\": \"Biochemical isolation and identification of the PTEX complex from P. falciparum\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — original complex identification replicated across multiple subsequent independent studies using Co-IP and biochemical fractionation\",\n      \"pmids\": [\"19536257\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"TRX2 adopts a canonical thioredoxin fold with significant structural differences in its N-terminus, and localizes to the parasitophorous vacuolar membrane (PVM) as shown by confocal microscopy.\",\n      \"method\": \"Crystal structure determination and confocal localization using GFP fusions\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1-2 / Weak — crystal structure plus confocal localization in a single lab study\",\n      \"pmids\": [\"22355694\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"TRX2 is a genuine PTEX member; TRX2 knockout parasites in P. berghei display reduced growth rates in vivo and in vitro and reduced capacity to cause severe disease in a cerebral malaria model, indicating TRX2 is not essential for parasite survival but helps optimize PTEX activity.\",\n      \"method\": \"Genetic deletion (knockout) in P. berghei with in vivo and in vitro growth assays and cerebral malaria phenotype analysis\",\n      \"journal\": \"Molecular microbiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — clean genetic knockout with defined cellular and in vivo phenotypes, replicated in a second independent study (PMID:24076174)\",\n      \"pmids\": [\"23869529\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium berghei\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"TRX2 knockout in P. berghei results in reduced blood-stage growth, though the deficit is less severe than for PTEX88 knockouts; endogenous tagging revealed TRX2::tag resides in distinct punctate organelles of unknown identity in blood stage parasites.\",\n      \"method\": \"Genetic deletion and endogenous tagging with flow cytometry-assisted intravital competition assay in P. berghei\",\n      \"journal\": \"Molecular and biochemical parasitology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — independent replication of TRX2 knockout growth phenotype, with direct localization by endogenous tagging in a single lab\",\n      \"pmids\": [\"24076174\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium berghei\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Parasites lacking TRX2 show greatly reduced trafficking of all classes of exported proteins (PEXEL and PEXEL-negative) beyond the double-membrane barrier, including the major virulence factor PfEMP1, establishing TRX2's role in protein translocation through PTEX.\",\n      \"method\": \"Analysis of a TRX2 knockout P. falciparum line combined with protein export assays\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — direct loss-of-function with defined molecular phenotype (export of multiple protein classes), reported in a high-impact study with multiple orthogonal assays\",\n      \"pmids\": [\"25043043\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"TRX2 crystal structure solved at 2.2-Å resolution reveals a canonical thioredoxin fold; SAXS and size exclusion chromatography demonstrate TRX2 is monomeric in solution; a non-conserved flexible N-terminal extension precedes the thioredoxin fold. The protein samples both redox catalytic states within the asymmetric unit, confirming its function as a protein disulfide reductase.\",\n      \"method\": \"X-ray crystallography (2.2 Å), size exclusion chromatography, and small-angle X-ray scattering (SAXS)\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — crystal structure with SAXS validation, multiple orthogonal biophysical methods in one study\",\n      \"pmids\": [\"25475729\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"TRX2-deficient P. berghei parasites show reduced sequestration to pulmonary, adipose, and brain tissue vasculature, yet remain virulent; this indicates TRX2 contributes to efficient tissue sequestration in vivo.\",\n      \"method\": \"Genetic deletion of TRX2 in P. berghei with in vivo tissue sequestration and virulence assays\",\n      \"journal\": \"Eukaryotic cell\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — clean knockout with defined in vivo phenotype, single lab but corroborates prior TRX2 knockout findings\",\n      \"pmids\": [\"25820521\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium berghei\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"The mitochondrial thioredoxin of P. falciparum (PfTrx2, the mitochondrial isoform characterized in this study, distinct from the PTEX component TRX2/PF3D7_1345100) acts as a reducing partner for the mitochondrial 2-Cys peroxiredoxin with a KM of 11.6 µM, much lower than for the cytosolic thioredoxin (PfTrx1, KM 130.4 µM), and both proteins localize to the mitochondrion by GFP fusion.\",\n      \"method\": \"Recombinant protein kinetic characterization (enzyme assay), GFP fusion localization in P. falciparum erythrocytic stages, and X-ray crystallography of the peroxiredoxin\",\n      \"journal\": \"Molecular microbiology\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 2 / Weak — NOTE: This paper uses 'PfTrx2' to refer to a mitochondrial thioredoxin; it is unclear whether this corresponds exactly to PF3D7_1345100 (PTEX TRX2) or a different locus; single lab, may be a different family member\",\n      \"pmids\": [\"16879648\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"Subcellular localization mapping of P. falciparum redox proteins demonstrated compartmentation of thioredoxin-like proteins; TRX2 (as part of the thioredoxin family survey) was shown to have distinct subcellular targeting, and thioredoxin reductase achieves dual localization via alternative translation initiation.\",\n      \"method\": \"Systematic subcellular localization study using fluorescent protein fusions in P. falciparum\",\n      \"journal\": \"PLoS pathogens\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — pan-redox-protein survey; TRX2-specific mechanistic detail is minimal; single lab\",\n      \"pmids\": [\"21203490\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"TRX2 is a poor substrate for thioredoxin reductase and lacks access to thioredoxin reductase; nevertheless, TRX2 can be reduced by the glutathione system (glutaredoxin/glutathione), demonstrating functional cross-talk between the glutathione and thioredoxin antioxidant systems in P. falciparum.\",\n      \"method\": \"In vitro biochemical reduction assays with recombinant proteins measuring cross-reactivity between glutathione and thioredoxin systems\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Weak — in vitro biochemical assay establishing enzymatic substrate relationship, single lab\",\n      \"pmids\": [\"28479253\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    }\n  ],\n  \"current_model\": \"TRX2 (PF3D7_1345100) is a monomeric protein disulfide reductase with a canonical thioredoxin fold (crystal structure resolved at 2.2 Å) that localizes to the parasitophorous vacuolar membrane as a non-essential but functionally important component of the PTEX complex; loss of TRX2 impairs export of all classes of parasite proteins into the host erythrocyte, reduces blood-stage growth, diminishes tissue sequestration in vivo, and reduces virulence in cerebral malaria models, while its enzymatic activity can be sustained by the glutathione system when thioredoxin reductase access is limiting.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"TRX2 (PF3D7_1345100) is a component of PTEX, the ATP-powered translocon in the parasitophorous vacuolar membrane (PVM) that exports parasite proteins into the host erythrocyte cytosol [#0, #1]. It adopts a canonical thioredoxin fold with a non-conserved flexible N-terminal extension, is monomeric in solution, and samples both redox catalytic states in the crystal, confirming its identity as a protein disulfide reductase [#5]. Functionally, TRX2 is non-essential but optimizes translocation: parasites lacking TRX2 show reduced trafficking of all classes of exported proteins beyond the double-membrane barrier, including the virulence factor PfEMP1 [#4], and in P. berghei TRX2 deletion causes reduced blood-stage growth, diminished tissue sequestration, and attenuated severe disease in a cerebral malaria model [#2, #6]. TRX2 is a poor substrate for thioredoxin reductase, but its reducing activity can be sustained by the glutathione/glutaredoxin system, linking it to the parasite's broader antioxidant network [#9]. The precise catalytic function TRX2 performs within the PTEX translocation cycle has not been resolved in the available corpus.\",\n  \"teleology\": [\n    {\n      \"year\": 2009,\n      \"claim\": \"Establishing that TRX2 is a bona fide subunit of an export machine answered where and in what context the protein operates, placing it in the protein-export pathway rather than a free cytosolic redox pool.\",\n      \"evidence\": \"Biochemical isolation and identification of the PTEX complex from P. falciparum\",\n      \"pmids\": [\"19536257\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Does not define TRX2's specific molecular contribution to translocation\", \"Stoichiometry and assembly order within PTEX unresolved\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Solving the fold and mapping subcellular location established TRX2 as a thioredoxin-fold protein resident at the PVM, consistent with its PTEX membership.\",\n      \"evidence\": \"Crystal structure determination and confocal localization of GFP fusions in P. falciparum\",\n      \"pmids\": [\"22355694\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Functional consequence of the divergent N-terminus unknown\", \"Localization based on GFP fusion in a single study\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Genetic deletion answered whether TRX2 is required for survival, showing it is dispensable but needed to optimize growth and full virulence.\",\n      \"evidence\": \"TRX2 knockout in P. berghei with in vivo/in vitro growth and cerebral malaria phenotype assays, independently replicated with endogenous tagging\",\n      \"pmids\": [\"23869529\", \"24076174\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Endogenous tag localized to punctate organelles of unknown identity\", \"Molecular basis of the growth deficit not defined\"],\n      \"attribution\": [{\"species\": \"Plasmodium berghei\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Loss-of-function export assays established that TRX2 is required for efficient translocation of all classes of exported proteins, defining its role at the mechanistic level of the export barrier.\",\n      \"evidence\": \"TRX2 knockout P. falciparum line combined with protein export assays for PEXEL and PEXEL-negative cargo including PfEMP1\",\n      \"pmids\": [\"25043043\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether TRX2 acts as a disulfide reductase on cargo or on the translocon during export is not resolved\", \"No direct substrate of TRX2 identified during translocation\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"High-resolution structural and biophysical analysis confirmed TRX2 is a monomeric protein disulfide reductase, providing the enzymatic identity underlying its export role.\",\n      \"evidence\": \"X-ray crystallography (2.2 Å), size-exclusion chromatography, and SAXS on recombinant TRX2\",\n      \"pmids\": [\"25475729\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Physiological substrate of the reductase activity not identified\", \"Structure does not reveal how TRX2 engages the PTEX translocon\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"In vivo sequestration assays showed TRX2 contributes to efficient tissue sequestration, connecting its export function to host-interaction phenotypes.\",\n      \"evidence\": \"TRX2 deletion in P. berghei with tissue sequestration and virulence assays\",\n      \"pmids\": [\"25820521\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Reduced sequestration not mechanistically linked to a specific exported adhesin in this system\", \"Parasites remained virulent, indicating partial redundancy\"],\n      \"attribution\": [{\"species\": \"Plasmodium berghei\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Biochemical reduction assays answered how TRX2 is kept reduced, showing it is a poor thioredoxin-reductase substrate but can be recycled by the glutathione system, revealing cross-talk between antioxidant systems.\",\n      \"evidence\": \"In vitro reduction assays with recombinant proteins measuring glutathione/thioredoxin system cross-reactivity in P. falciparum\",\n      \"pmids\": [\"28479253\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether glutathione-dependent recycling operates at the PVM in vivo is untested\", \"Physiological electron donor during export not established\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The specific disulfide-bond substrate and catalytic step TRX2 performs within the PTEX translocation cycle remain unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No cargo or translocon substrate of TRX2's reductase activity identified during export\", \"Mechanistic link between reductase activity and translocation efficiency unproven\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0015035\", \"supporting_discovery_ids\": [5, 9]},\n      {\"term_id\": \"GO:0015036\", \"supporting_discovery_ids\": [5]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0020005\", \"supporting_discovery_ids\": [0, 1]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"GO:0065002\", \"supporting_discovery_ids\": [0, 4]}\n    ],\n    \"complexes\": [\n      \"PTEX (Plasmodium translocon of exported proteins)\"\n    ],\n    \"partners\": [],\n    \"other_free_text\": [\n      \"Non-essential in P. berghei; knockout reduces blood-stage growth, tissue sequestration, and severe-disease capacity [#2, #3, #6]\",\n      \"Required for efficient export of PEXEL and PEXEL-negative proteins including PfEMP1 in P. falciparum [#4]\",\n      \"Monomeric with canonical thioredoxin fold and divergent flexible N-terminal extension [#5, #1]\",\n      \"Poor thioredoxin reductase substrate; reducible by the glutathione/glutaredoxin system [#9]\",\n      \"Idx 7 describes a mitochondrial thioredoxin (referred to as PfTrx2) that may be a distinct locus from PF3D7_1345100 and is excluded from the TRX2 mechanistic claims\"\n    ]\n  }\n}","audit_flag":null,"strains":[{"strain":"Pf3D7","gene_id":"PF3D7_1345100","name":null,"product":"thioredoxin 2","uniprot_acc":null,"chromosome":null,"start_pos":null},{"strain":"PbANKA","gene_id":"PBANKA_1358000","name":null,"product":"thioredoxin 2","uniprot_acc":null,"chromosome":null,"start_pos":null},{"strain":"PkH","gene_id":"PKNH_1256200","name":null,"product":"thioredoxin 2, putative","uniprot_acc":null,"chromosome":null,"start_pos":null}],"gene_symbol":"TRX2","evaluation":null}