{"gene":"PF3D7_1457200","run_date":"2026-09-08T14:19:07","timeline":{"discoveries":[{"year":2000,"finding":"TRX1 (PfTrx, 13 kDa) was cloned, expressed, and biochemically characterized. It has a midpoint redox potential of -270 mV and is reduced by both P. falciparum TrxR (Km = 10.4 µM, kcat = 3100 min⁻¹) and human TrxR (Km = 2 µM, kcat = 3300 min⁻¹). Reduced TRX1 reduces GSSG with a rate constant k2 = 0.039 µM⁻¹ min⁻¹, approximately 5-fold faster than thioredoxins from human, Drosophila, or E. coli, and also reduces S-nitrosoglutathione.","method":"Recombinant protein expression, steady-state enzyme kinetics, redox potential measurement","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro biochemical reconstitution with kinetic parameters, replicated across multiple coupled assay systems in a single rigorous study","pmids":["11013257"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2001,"finding":"TRX1 active-site cysteines (Cys30 and Cys33) are both essential for catalytic activity as shown by mutational analyses. A third cysteine (Cys43) outside the active site is partially responsible for dimer formation; mutating Cys43 to Ala reduces dimerization. All three cysteines are accessible to DTNB modification, with Cys33 more reactive than Cys30. Steady-state kinetics with PfTrxR give Km values of 0.8–2.1 µM for TRX1, ~250-fold lower than for E. coli thioredoxin.","method":"Site-directed mutagenesis, DTNB reactivity assay, steady-state kinetics with recombinant PfTrxR","journal":"Molecular and biochemical parasitology","confidence":"High","confidence_rationale":"Tier 1 / Strong — active-site mutagenesis combined with in vitro enzymatic assays in a single focused study","pmids":["11223129"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2006,"finding":"The mitochondrial peroxiredoxin of P. falciparum strongly prefers the mitochondrial thioredoxin (PfTrx2) over the cytosolic TRX1 as a reducing partner (Km 11.6 µM vs. 130.4 µM for TRX1). Substitution of residues Asn62/Tyr63 and Phe139/Ala140 in the peroxiredoxin reduced the Km for TRX1 but had no effect on Km for PfTrx2, indicating these residues mediate substrate discrimination.","method":"Recombinant protein expression, steady-state kinetics, site-directed mutagenesis of the peroxiredoxin","journal":"Molecular microbiology","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro kinetic reconstitution with mutagenesis, single lab but multiple orthogonal methods","pmids":["16879648"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2009,"finding":"Human peroxiredoxin 2 (hPrx-2), imported into the P. falciparum cytosol, accepts cytosolic TRX1 as a reducing substrate in enzyme kinetic analyses, accounting for roughly 50% of thioredoxin peroxidase activity in parasite extracts.","method":"Enzyme kinetic analysis with recombinant proteins, confocal microscopy, immunogold electron microscopy","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro enzymatic reconstitution with multiple orthogonal validation methods (kinetics, confocal, immunogold EM)","pmids":["19666612"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2009,"finding":"Using an active-site mutant of TRX1 lacking the resolving cysteine (to trap substrates via mixed disulfide), 17 putative redox-regulated target proteins of TRX1 were identified by affinity chromatography and mass spectrometry, including proteins in protein biosynthesis, energy metabolism, and signal transduction. TRX1 binding to S-adenosyl-L-homocysteine hydrolase and ornithine aminotransferase (OAT) was verified by surface plasmon resonance (BIAcore), and TRX1 was shown to enhance OAT enzymatic activity in functional assays.","method":"Active-site mutant affinity chromatography, mass spectrometry, BIAcore surface plasmon resonance, enzymatic activity assay","journal":"PLoS pathogens","confidence":"High","confidence_rationale":"Tier 1–2 / Moderate — trapping strategy with MS plus SPR and enzymatic validation, single lab with multiple orthogonal methods","pmids":["19360125"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2010,"finding":"TRX1 localizes to the cytoplasm of P. falciparum blood-stage parasites. Using alternative translation initiation, thioredoxin reductase (TrxR) achieves dual cytosolic and mitochondrial localization, providing TRX1's electron donor in the cytosol.","method":"Systematic subcellular localization study using GFP fusions and confocal microscopy","journal":"PLoS pathogens","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct GFP-fusion localization experiments; cytosolic localization of TRX1 itself was confirmed, functional consequence inferred from system-level mapping","pmids":["21203490"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2010,"finding":"TRX1 activates P. falciparum OAT activity approximately 10-fold. Crystal structure of OAT and site-directed mutagenesis identified Cys154 and Cys163 (within the substrate-binding loop, absent in human OAT) as the residues that mediate interaction with TRX1; the Cys154→Ser mutant shows strongly reduced OAT activity due to impaired ornithine binding.","method":"Crystal structure of OAT (2.3 Å), site-directed mutagenesis of OAT cysteines, enzymatic activity assays with recombinant TRX1","journal":"Journal of molecular biology","confidence":"High","confidence_rationale":"Tier 1 / Moderate — crystal structure combined with mutagenesis and in vitro enzymatic activation assay, single lab with multiple orthogonal methods","pmids":["20673832"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2010,"finding":"Affinity chromatography with a resolving-cysteine mutant of TRX1 (C33S) captured 20 target proteins from P. falciparum extracts, including four glycolytic enzymes (hexokinase, GAPDH, phosphoglycerate mutase, LDH). TRX1 enhanced the enzymatic activity of PfGAPDH and PfLDH in functional assays.","method":"Cysteine-mutant affinity chromatography, LC-MS/MS, enzymatic activity assay","journal":"Parasitology international","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — trapping chromatography with MS plus enzymatic validation, single lab, two orthogonal methods","pmids":["20307687"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2011,"finding":"TRX1 (thioredoxin 1) efficiently catalyzes protein deglutathionylation in P. falciparum, demonstrated by enzymatic deglutathionylation assays. TRX1 was itself identified as a target of S-glutathionylation in the parasite glutathionylome.","method":"Enzymatic deglutathionylation assay, affinity purification with biotin-maleimide, proteomic analysis by mass spectrometry","journal":"Antioxidants & redox signaling","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vitro enzymatic assay plus proteomic identification, single lab, two orthogonal methods","pmids":["21595565"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2013,"finding":"Crystal structure of the P. falciparum TrxR–TRX1 complex was solved, revealing that complex formation induces rearrangements of the TrxR flexible C-terminal arm and an insertion loop. Amino acid residues at the TrxR–TRX1 interface were functionally analyzed by mutagenesis. The structure shows how TRX1 is bound and reduced by PfTrxR, with key differences from the human TrxR–thioredoxin interface.","method":"X-ray crystallography (crystal structure of TrxR–TRX1 complex), active-site mutagenesis, cell biological inhibitor experiments","journal":"Journal of molecular biology","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structure of the protein complex with functional mutagenesis validation in a single rigorous study","pmids":["23845423"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2014,"finding":"TRX1 (PfTrx1) can be S-nitrosylated at its non-active-site cysteine (Cys43). Mechanistic studies demonstrated that TRX1 possesses both denitrosylating activity (mediated by active-site cysteines Cys30/Cys33) and transnitrosylating activity (mediated by Cys43).","method":"Biotin-switch assay, mass spectrometry, mechanistic mutagenesis/functional assays","journal":"Antioxidants & redox signaling","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — biotin-switch plus mechanistic functional analyses distinguishing active-site vs. non-active-site cysteine roles, single lab","pmids":["24256207"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2024,"finding":"Solution structures of TRX1 in both reduced and oxidized forms were determined by high-resolution NMR. The protein adopts an α/β-fold with a mixed five-stranded β-sheet sandwiched between 4 helices (β1α1β2α2β3α3β4β5α4 topology). Oxidation of the CGPC active-site motif (Cys30–Cys33 disulfide) induces significant structural changes in residues Phe25–Ile36, Thr70–Thr74, and Leu88–Asn91. High-pressure NMR identifies at least three coexisting conformational sub-states in both redox forms.","method":"High-resolution NMR (solution structure determination of ¹³C/¹⁵N-labeled protein), high-pressure NMR spectroscopy","journal":"PloS one","confidence":"High","confidence_rationale":"Tier 1 / Moderate — full NMR structure determination in both redox states with pressure-dependent conformational analysis; single lab but comprehensive structural methodology","pmids":["38635664"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]}],"current_model":"P. falciparum TRX1 is a cytosolic 13-kDa thioredoxin with the active-site motif CGPC (Cys30–Cys33) whose structure has been solved by NMR (reduced and oxidized) and in complex with TrxR by X-ray crystallography; it is reduced by PfTrxR (and cross-reacts with human TrxR), reduces GSSG and S-nitrosoglutathione, activates OAT ~10-fold via Cys154/Cys163 on OAT, enhances GAPDH and LDH activity, catalyzes protein deglutathionylation, and mediates both denitrosylation (via active-site cysteines) and transnitrosylation (via non-active-site Cys43), with at least 17–20 redox-regulated target proteins identified by trapping chromatography."},"narrative":{"mechanistic_narrative":"PF3D7_1457200 (TRX1) is a cytosolic ~13-kDa thioredoxin that serves as a central electron-shuttling hub of the P. falciparum redox network, coupling the NADPH-dependent reductase system to a broad set of downstream target proteins [PMID:11013257, PMID:19360125]. It carries a CGPC active-site motif (Cys30–Cys33) whose two cysteines are both essential for catalysis, plus a non-active-site Cys43 that mediates dimer formation [PMID:11223129, PMID:38635664]. TRX1 is reduced with high efficiency by P. falciparum TrxR and also cross-reacts with human TrxR; the crystal structure of the PfTrxR–TRX1 complex shows that binding induces rearrangements of the reductase C-terminal arm and insertion loop, with an interface distinct from the human counterpart [PMID:11013257, PMID:23845423]. Once reduced, TRX1 reduces GSSG (roughly five-fold faster than orthologous thioredoxins) and S-nitrosoglutathione, and hands electrons to peroxiredoxin partners, including an imported human peroxiredoxin 2 [PMID:11013257, PMID:19666612]. Beyond canonical disulfide reduction, TRX1 acts as a redox regulator of metabolic enzymes: trapping chromatography with resolving-cysteine mutants captured ~17–20 target proteins spanning protein biosynthesis, energy metabolism, and signal transduction, and TRX1 activates ornithine aminotransferase ~10-fold (via OAT Cys154/Cys163) and enhances GAPDH and LDH activity [PMID:19360125, PMID:20673832, PMID:20307687]. TRX1 additionally catalyzes protein deglutathionylation, is itself a glutathionylation target, and mediates both denitrosylation (via Cys30/Cys33) and transnitrosylation (via Cys43) [PMID:21595565, PMID:24256207]. Solution NMR structures of both redox states reveal a canonical thioredoxin α/β-fold with oxidation-coupled conformational changes and multiple coexisting sub-states [PMID:38635664].","teleology":[{"year":2000,"claim":"Establishing that TRX1 is a bona fide, kinetically efficient thioredoxin was the necessary first step to place it within the parasite's NADPH-driven redox chain.","evidence":"Recombinant expression, steady-state kinetics, and redox potential measurement with both P. falciparum and human TrxR","pmids":["11013257"],"confidence":"High","gaps":["Physiological in vivo substrates not yet defined","Cellular role during infection not addressed"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2001,"claim":"Mutational dissection defined which cysteines drive catalysis versus oligomerization, mapping the functional chemistry onto specific residues.","evidence":"Site-directed mutagenesis, DTNB reactivity assay, and steady-state kinetics with recombinant PfTrxR","pmids":["11223129"],"confidence":"High","gaps":["Functional significance of Cys43-mediated dimerization in vivo unresolved"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2006,"claim":"Comparing peroxiredoxin preference resolved the compartmental division of labor between cytosolic TRX1 and mitochondrial PfTrx2 as reducing partners.","evidence":"Recombinant kinetics and peroxiredoxin mutagenesis showing weak preference of mitochondrial Prx for TRX1","pmids":["16879648"],"confidence":"High","gaps":["Physiological flux through TRX1-Prx couple in living parasites not quantified"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2009,"claim":"Trapping-based target capture transformed TRX1 from a generic disulfide reductase into a defined regulator by naming ~17 candidate substrates and validating direct binding and functional activation.","evidence":"Active-site-trap affinity chromatography, mass spectrometry, BIAcore SPR, and OAT enzymatic assay","pmids":["19360125"],"confidence":"High","gaps":["Most captured targets lack functional validation","In vivo redox regulation of these targets untested"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2009,"claim":"Demonstrating that imported human Prx-2 uses TRX1 tied the parasite thioredoxin system to host-derived peroxidase capacity.","evidence":"Enzyme kinetics with recombinant proteins plus confocal and immunogold EM","pmids":["19666612"],"confidence":"High","gaps":["Contribution to parasite survival under oxidative stress not measured"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2010,"claim":"Localizing TRX1 to the cytosol and mapping TrxR's dual targeting confirmed where TRX1 acts and how its electron donor reaches it.","evidence":"GFP-fusion subcellular localization by confocal microscopy","pmids":["21203490"],"confidence":"Medium","gaps":["Functional consequence of TrxR dual localization inferred, not directly demonstrated for TRX1"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2010,"claim":"Structural and mutational work on OAT provided the mechanistic basis for TRX1-dependent activation of a metabolic enzyme via parasite-specific cysteines absent in the human ortholog.","evidence":"OAT crystal structure, cysteine mutagenesis, and enzymatic activation assays with recombinant TRX1","pmids":["20673832"],"confidence":"High","gaps":["In vivo relevance of TRX1-OAT activation to polyamine/proline metabolism untested"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2010,"claim":"A second trapping screen extended TRX1's regulatory reach to central glycolysis, showing it enhances GAPDH and LDH activity.","evidence":"C33S-mutant affinity chromatography, LC-MS/MS, and enzymatic activity assays","pmids":["20307687"],"confidence":"Medium","gaps":["Whether these targets are redox-regulated under physiological conditions unknown","Overlap/redundancy among captured targets not resolved"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2011,"claim":"Identifying deglutathionylase activity and TRX1's own glutathionylation broadened its function to reversible protein S-glutathionylation control.","evidence":"Enzymatic deglutathionylation assays and glutathionylome proteomics by mass spectrometry","pmids":["21595565"],"confidence":"Medium","gaps":["Physiological deglutathionylation substrates not defined","Regulatory role of TRX1 self-glutathionylation unclear"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2014,"claim":"Distinguishing active-site-mediated denitrosylation from Cys43-mediated transnitrosylation established TRX1 as a bidirectional player in nitrosative signaling.","evidence":"Biotin-switch assay, mass spectrometry, and mechanistic mutagenesis of active-site versus Cys43","pmids":["24256207"],"confidence":"Medium","gaps":["Cellular targets of TRX1 trans-/denitrosylation unidentified","In vivo balance of the two activities unknown"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2024,"claim":"High-resolution NMR structures in both redox states provided an atomic and dynamic framework linking active-site oxidation to defined conformational transitions.","evidence":"Solution NMR structure determination and high-pressure NMR of reduced and oxidized TRX1","pmids":["38635664"],"confidence":"High","gaps":["Structural basis of target selectivity not addressed","Conformational sub-states not linked to specific catalytic steps"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":null,"claim":"The in vivo essentiality of TRX1 and the physiological relevance of its captured metabolic and nitrosative targets during infection remain open.","evidence":"","pmids":[],"confidence":"Low","gaps":["No genetic knockout/knockdown phenotype in the corpus","Which captured targets are regulated by TRX1 in living parasites is unresolved"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]}],"mechanism_profile":{"molecular_activity":[],"localization":[],"pathway":[],"complexes":["PfTrxR–TRX1 reductase complex [#9]"],"partners":["THIOREDOXIN REDUCTASE / PFTRXR [#0, #9]","HUMAN THIOREDOXIN REDUCTASE (CROSS-REACTIVE) [#0]","MITOCHONDRIAL PEROXIREDOXIN (WEAK PARTNER, PREFERS PFTRX2) [#2]","HUMAN PEROXIREDOXIN 2 (IMPORTED) [#3]","ORNITHINE AMINOTRANSFERASE (OAT) [#4, #6]","S-ADENOSYL-L-HOMOCYSTEINE HYDROLASE [#4]","GAPDH [#7]","LDH [#7]","HEXOKINASE [#7]","PHOSPHOGLYCERATE MUTASE [#7]"],"other_free_text":["Active-site motif CGPC (Cys30–Cys33); both cysteines essential for catalysis [#1, #11]","Non-active-site Cys43 mediates dimerization and transnitrosylation [#1, #10]","Midpoint redox potential -270 mV; reduces GSSG ~5-fold faster than human/Drosophila/E. coli thioredoxins [#0]","Activates OAT ~10-fold via OAT Cys154/Cys163 [#6]","~17–20 redox-regulated targets identified by resolving-cysteine trapping chromatography [#4, #7]","Canonical thioredoxin α/β-fold; oxidation-coupled conformational changes and multiple sub-states by NMR [#11]"]}},"prefetch_data":{},"corpus_meta":[{"pmid":"11013257","id":"PMC_11013257","title":"The thioredoxin system of the malaria parasite Plasmodium falciparum. Glutathione reduction revisited.","date":"2000","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/11013257","citation_count":201,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["curated_ref"],"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":"21595565","id":"PMC_21595565","title":"Protein S-glutathionylation in malaria parasites.","date":"2011","source":"Antioxidants & redox 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1","PfTRX1"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":11438,"output_tokens":3711,"usd":0.04499,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":9581,"output_tokens":4237,"usd":0.076915,"stage2_stop_reason":"end_turn"},"total_usd":0.121905,"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\": 2000,\n      \"finding\": \"TRX1 (PfTrx, 13 kDa) was cloned, expressed, and biochemically characterized. It has a midpoint redox potential of -270 mV and is reduced by both P. falciparum TrxR (Km = 10.4 µM, kcat = 3100 min⁻¹) and human TrxR (Km = 2 µM, kcat = 3300 min⁻¹). Reduced TRX1 reduces GSSG with a rate constant k2 = 0.039 µM⁻¹ min⁻¹, approximately 5-fold faster than thioredoxins from human, Drosophila, or E. coli, and also reduces S-nitrosoglutathione.\",\n      \"method\": \"Recombinant protein expression, steady-state enzyme kinetics, redox potential measurement\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro biochemical reconstitution with kinetic parameters, replicated across multiple coupled assay systems in a single rigorous study\",\n      \"pmids\": [\"11013257\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"TRX1 active-site cysteines (Cys30 and Cys33) are both essential for catalytic activity as shown by mutational analyses. A third cysteine (Cys43) outside the active site is partially responsible for dimer formation; mutating Cys43 to Ala reduces dimerization. All three cysteines are accessible to DTNB modification, with Cys33 more reactive than Cys30. Steady-state kinetics with PfTrxR give Km values of 0.8–2.1 µM for TRX1, ~250-fold lower than for E. coli thioredoxin.\",\n      \"method\": \"Site-directed mutagenesis, DTNB reactivity assay, steady-state kinetics with recombinant PfTrxR\",\n      \"journal\": \"Molecular and biochemical parasitology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — active-site mutagenesis combined with in vitro enzymatic assays in a single focused study\",\n      \"pmids\": [\"11223129\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"The mitochondrial peroxiredoxin of P. falciparum strongly prefers the mitochondrial thioredoxin (PfTrx2) over the cytosolic TRX1 as a reducing partner (Km 11.6 µM vs. 130.4 µM for TRX1). Substitution of residues Asn62/Tyr63 and Phe139/Ala140 in the peroxiredoxin reduced the Km for TRX1 but had no effect on Km for PfTrx2, indicating these residues mediate substrate discrimination.\",\n      \"method\": \"Recombinant protein expression, steady-state kinetics, site-directed mutagenesis of the peroxiredoxin\",\n      \"journal\": \"Molecular microbiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro kinetic reconstitution with mutagenesis, single lab but multiple orthogonal methods\",\n      \"pmids\": [\"16879648\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Human peroxiredoxin 2 (hPrx-2), imported into the P. falciparum cytosol, accepts cytosolic TRX1 as a reducing substrate in enzyme kinetic analyses, accounting for roughly 50% of thioredoxin peroxidase activity in parasite extracts.\",\n      \"method\": \"Enzyme kinetic analysis with recombinant proteins, confocal microscopy, immunogold electron microscopy\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro enzymatic reconstitution with multiple orthogonal validation methods (kinetics, confocal, immunogold EM)\",\n      \"pmids\": [\"19666612\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Using an active-site mutant of TRX1 lacking the resolving cysteine (to trap substrates via mixed disulfide), 17 putative redox-regulated target proteins of TRX1 were identified by affinity chromatography and mass spectrometry, including proteins in protein biosynthesis, energy metabolism, and signal transduction. TRX1 binding to S-adenosyl-L-homocysteine hydrolase and ornithine aminotransferase (OAT) was verified by surface plasmon resonance (BIAcore), and TRX1 was shown to enhance OAT enzymatic activity in functional assays.\",\n      \"method\": \"Active-site mutant affinity chromatography, mass spectrometry, BIAcore surface plasmon resonance, enzymatic activity assay\",\n      \"journal\": \"PLoS pathogens\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — trapping strategy with MS plus SPR and enzymatic validation, single lab with multiple orthogonal methods\",\n      \"pmids\": [\"19360125\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"TRX1 localizes to the cytoplasm of P. falciparum blood-stage parasites. Using alternative translation initiation, thioredoxin reductase (TrxR) achieves dual cytosolic and mitochondrial localization, providing TRX1's electron donor in the cytosol.\",\n      \"method\": \"Systematic subcellular localization study using GFP fusions and confocal microscopy\",\n      \"journal\": \"PLoS pathogens\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct GFP-fusion localization experiments; cytosolic localization of TRX1 itself was confirmed, functional consequence inferred from system-level mapping\",\n      \"pmids\": [\"21203490\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"TRX1 activates P. falciparum OAT activity approximately 10-fold. Crystal structure of OAT and site-directed mutagenesis identified Cys154 and Cys163 (within the substrate-binding loop, absent in human OAT) as the residues that mediate interaction with TRX1; the Cys154→Ser mutant shows strongly reduced OAT activity due to impaired ornithine binding.\",\n      \"method\": \"Crystal structure of OAT (2.3 Å), site-directed mutagenesis of OAT cysteines, enzymatic activity assays with recombinant TRX1\",\n      \"journal\": \"Journal of molecular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — crystal structure combined with mutagenesis and in vitro enzymatic activation assay, single lab with multiple orthogonal methods\",\n      \"pmids\": [\"20673832\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"Affinity chromatography with a resolving-cysteine mutant of TRX1 (C33S) captured 20 target proteins from P. falciparum extracts, including four glycolytic enzymes (hexokinase, GAPDH, phosphoglycerate mutase, LDH). TRX1 enhanced the enzymatic activity of PfGAPDH and PfLDH in functional assays.\",\n      \"method\": \"Cysteine-mutant affinity chromatography, LC-MS/MS, enzymatic activity assay\",\n      \"journal\": \"Parasitology international\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — trapping chromatography with MS plus enzymatic validation, single lab, two orthogonal methods\",\n      \"pmids\": [\"20307687\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"TRX1 (thioredoxin 1) efficiently catalyzes protein deglutathionylation in P. falciparum, demonstrated by enzymatic deglutathionylation assays. TRX1 was itself identified as a target of S-glutathionylation in the parasite glutathionylome.\",\n      \"method\": \"Enzymatic deglutathionylation assay, affinity purification with biotin-maleimide, proteomic analysis by mass spectrometry\",\n      \"journal\": \"Antioxidants & redox signaling\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vitro enzymatic assay plus proteomic identification, single lab, two orthogonal methods\",\n      \"pmids\": [\"21595565\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Crystal structure of the P. falciparum TrxR–TRX1 complex was solved, revealing that complex formation induces rearrangements of the TrxR flexible C-terminal arm and an insertion loop. Amino acid residues at the TrxR–TRX1 interface were functionally analyzed by mutagenesis. The structure shows how TRX1 is bound and reduced by PfTrxR, with key differences from the human TrxR–thioredoxin interface.\",\n      \"method\": \"X-ray crystallography (crystal structure of TrxR–TRX1 complex), active-site mutagenesis, cell biological inhibitor experiments\",\n      \"journal\": \"Journal of molecular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structure of the protein complex with functional mutagenesis validation in a single rigorous study\",\n      \"pmids\": [\"23845423\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"TRX1 (PfTrx1) can be S-nitrosylated at its non-active-site cysteine (Cys43). Mechanistic studies demonstrated that TRX1 possesses both denitrosylating activity (mediated by active-site cysteines Cys30/Cys33) and transnitrosylating activity (mediated by Cys43).\",\n      \"method\": \"Biotin-switch assay, mass spectrometry, mechanistic mutagenesis/functional assays\",\n      \"journal\": \"Antioxidants & redox signaling\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — biotin-switch plus mechanistic functional analyses distinguishing active-site vs. non-active-site cysteine roles, single lab\",\n      \"pmids\": [\"24256207\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Solution structures of TRX1 in both reduced and oxidized forms were determined by high-resolution NMR. The protein adopts an α/β-fold with a mixed five-stranded β-sheet sandwiched between 4 helices (β1α1β2α2β3α3β4β5α4 topology). Oxidation of the CGPC active-site motif (Cys30–Cys33 disulfide) induces significant structural changes in residues Phe25–Ile36, Thr70–Thr74, and Leu88–Asn91. High-pressure NMR identifies at least three coexisting conformational sub-states in both redox forms.\",\n      \"method\": \"High-resolution NMR (solution structure determination of ¹³C/¹⁵N-labeled protein), high-pressure NMR spectroscopy\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — full NMR structure determination in both redox states with pressure-dependent conformational analysis; single lab but comprehensive structural methodology\",\n      \"pmids\": [\"38635664\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    }\n  ],\n  \"current_model\": \"P. falciparum TRX1 is a cytosolic 13-kDa thioredoxin with the active-site motif CGPC (Cys30–Cys33) whose structure has been solved by NMR (reduced and oxidized) and in complex with TrxR by X-ray crystallography; it is reduced by PfTrxR (and cross-reacts with human TrxR), reduces GSSG and S-nitrosoglutathione, activates OAT ~10-fold via Cys154/Cys163 on OAT, enhances GAPDH and LDH activity, catalyzes protein deglutathionylation, and mediates both denitrosylation (via active-site cysteines) and transnitrosylation (via non-active-site Cys43), with at least 17–20 redox-regulated target proteins identified by trapping chromatography.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"PF3D7_1457200 (TRX1) is a cytosolic ~13-kDa thioredoxin that serves as a central electron-shuttling hub of the P. falciparum redox network, coupling the NADPH-dependent reductase system to a broad set of downstream target proteins [#0, #4]. It carries a CGPC active-site motif (Cys30\\u2013Cys33) whose two cysteines are both essential for catalysis, plus a non-active-site Cys43 that mediates dimer formation [#1, #11]. TRX1 is reduced with high efficiency by P. falciparum TrxR and also cross-reacts with human TrxR; the crystal structure of the PfTrxR\\u2013TRX1 complex shows that binding induces rearrangements of the reductase C-terminal arm and insertion loop, with an interface distinct from the human counterpart [#0, #9]. Once reduced, TRX1 reduces GSSG (roughly five-fold faster than orthologous thioredoxins) and S-nitrosoglutathione, and hands electrons to peroxiredoxin partners, including an imported human peroxiredoxin 2 [#0, #3]. Beyond canonical disulfide reduction, TRX1 acts as a redox regulator of metabolic enzymes: trapping chromatography with resolving-cysteine mutants captured ~17\\u201320 target proteins spanning protein biosynthesis, energy metabolism, and signal transduction, and TRX1 activates ornithine aminotransferase ~10-fold (via OAT Cys154/Cys163) and enhances GAPDH and LDH activity [#4, #6, #7]. TRX1 additionally catalyzes protein deglutathionylation, is itself a glutathionylation target, and mediates both denitrosylation (via Cys30/Cys33) and transnitrosylation (via Cys43) [#8, #10]. Solution NMR structures of both redox states reveal a canonical thioredoxin \\u03b1/\\u03b2-fold with oxidation-coupled conformational changes and multiple coexisting sub-states [#11].\",\n  \"teleology\": [\n    {\n      \"year\": 2000,\n      \"claim\": \"Establishing that TRX1 is a bona fide, kinetically efficient thioredoxin was the necessary first step to place it within the parasite's NADPH-driven redox chain.\",\n      \"evidence\": \"Recombinant expression, steady-state kinetics, and redox potential measurement with both P. falciparum and human TrxR\",\n      \"pmids\": [\"11013257\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Physiological in vivo substrates not yet defined\", \"Cellular role during infection not addressed\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2001,\n      \"claim\": \"Mutational dissection defined which cysteines drive catalysis versus oligomerization, mapping the functional chemistry onto specific residues.\",\n      \"evidence\": \"Site-directed mutagenesis, DTNB reactivity assay, and steady-state kinetics with recombinant PfTrxR\",\n      \"pmids\": [\"11223129\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Functional significance of Cys43-mediated dimerization in vivo unresolved\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Comparing peroxiredoxin preference resolved the compartmental division of labor between cytosolic TRX1 and mitochondrial PfTrx2 as reducing partners.\",\n      \"evidence\": \"Recombinant kinetics and peroxiredoxin mutagenesis showing weak preference of mitochondrial Prx for TRX1\",\n      \"pmids\": [\"16879648\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Physiological flux through TRX1-Prx couple in living parasites not quantified\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Trapping-based target capture transformed TRX1 from a generic disulfide reductase into a defined regulator by naming ~17 candidate substrates and validating direct binding and functional activation.\",\n      \"evidence\": \"Active-site-trap affinity chromatography, mass spectrometry, BIAcore SPR, and OAT enzymatic assay\",\n      \"pmids\": [\"19360125\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Most captured targets lack functional validation\", \"In vivo redox regulation of these targets untested\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Demonstrating that imported human Prx-2 uses TRX1 tied the parasite thioredoxin system to host-derived peroxidase capacity.\",\n      \"evidence\": \"Enzyme kinetics with recombinant proteins plus confocal and immunogold EM\",\n      \"pmids\": [\"19666612\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Contribution to parasite survival under oxidative stress not measured\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Localizing TRX1 to the cytosol and mapping TrxR's dual targeting confirmed where TRX1 acts and how its electron donor reaches it.\",\n      \"evidence\": \"GFP-fusion subcellular localization by confocal microscopy\",\n      \"pmids\": [\"21203490\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Functional consequence of TrxR dual localization inferred, not directly demonstrated for TRX1\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Structural and mutational work on OAT provided the mechanistic basis for TRX1-dependent activation of a metabolic enzyme via parasite-specific cysteines absent in the human ortholog.\",\n      \"evidence\": \"OAT crystal structure, cysteine mutagenesis, and enzymatic activation assays with recombinant TRX1\",\n      \"pmids\": [\"20673832\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"In vivo relevance of TRX1-OAT activation to polyamine/proline metabolism untested\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"A second trapping screen extended TRX1's regulatory reach to central glycolysis, showing it enhances GAPDH and LDH activity.\",\n      \"evidence\": \"C33S-mutant affinity chromatography, LC-MS/MS, and enzymatic activity assays\",\n      \"pmids\": [\"20307687\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether these targets are redox-regulated under physiological conditions unknown\", \"Overlap/redundancy among captured targets not resolved\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Identifying deglutathionylase activity and TRX1's own glutathionylation broadened its function to reversible protein S-glutathionylation control.\",\n      \"evidence\": \"Enzymatic deglutathionylation assays and glutathionylome proteomics by mass spectrometry\",\n      \"pmids\": [\"21595565\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Physiological deglutathionylation substrates not defined\", \"Regulatory role of TRX1 self-glutathionylation unclear\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Distinguishing active-site-mediated denitrosylation from Cys43-mediated transnitrosylation established TRX1 as a bidirectional player in nitrosative signaling.\",\n      \"evidence\": \"Biotin-switch assay, mass spectrometry, and mechanistic mutagenesis of active-site versus Cys43\",\n      \"pmids\": [\"24256207\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Cellular targets of TRX1 trans-/denitrosylation unidentified\", \"In vivo balance of the two activities unknown\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"High-resolution NMR structures in both redox states provided an atomic and dynamic framework linking active-site oxidation to defined conformational transitions.\",\n      \"evidence\": \"Solution NMR structure determination and high-pressure NMR of reduced and oxidized TRX1\",\n      \"pmids\": [\"38635664\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of target selectivity not addressed\", \"Conformational sub-states not linked to specific catalytic steps\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The in vivo essentiality of TRX1 and the physiological relevance of its captured metabolic and nitrosative targets during infection remain open.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No genetic knockout/knockdown phenotype in the corpus\", \"Which captured targets are regulated by TRX1 in living parasites is unresolved\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0015035\", \"supporting_discovery_ids\": [0, 1, 9]},\n      {\"term_id\": \"GO:0045454\", \"supporting_discovery_ids\": [0, 3, 8]},\n      {\"term_id\": \"GO:0035595\", \"supporting_discovery_ids\": [8]},\n      {\"term_id\": \"GO:0035605\", \"supporting_discovery_ids\": [10]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [5]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"GO:0034599\", \"supporting_discovery_ids\": [0, 3]},\n      {\"term_id\": \"GO:0006979\", \"supporting_discovery_ids\": [0, 8, 10]}\n    ],\n    \"complexes\": [\n      \"PfTrxR\\u2013TRX1 reductase complex [#9]\"\n    ],\n    \"partners\": [\n      \"Thioredoxin reductase / PfTrxR [#0, #9]\",\n      \"Human thioredoxin reductase (cross-reactive) [#0]\",\n      \"Mitochondrial peroxiredoxin (weak partner, prefers PfTrx2) [#2]\",\n      \"Human peroxiredoxin 2 (imported) [#3]\",\n      \"Ornithine aminotransferase (OAT) [#4, #6]\",\n      \"S-adenosyl-L-homocysteine hydrolase [#4]\",\n      \"GAPDH [#7]\",\n      \"LDH [#7]\",\n      \"Hexokinase [#7]\",\n      \"Phosphoglycerate mutase [#7]\"\n    ],\n    \"other_free_text\": [\n      \"Active-site motif CGPC (Cys30\\u2013Cys33); both cysteines essential for catalysis [#1, #11]\",\n      \"Non-active-site Cys43 mediates dimerization and transnitrosylation [#1, #10]\",\n      \"Midpoint redox potential -270 mV; reduces GSSG ~5-fold faster than human/Drosophila/E. coli thioredoxins [#0]\",\n      \"Activates OAT ~10-fold via OAT Cys154/Cys163 [#6]\",\n      \"~17\\u201320 redox-regulated targets identified by resolving-cysteine trapping chromatography [#4, #7]\",\n      \"Canonical thioredoxin \\u03b1/\\u03b2-fold; oxidation-coupled conformational changes and multiple sub-states by NMR [#11]\"\n    ]\n  }\n}","audit_flag":null,"strains":[{"strain":"Pf3D7","gene_id":"PF3D7_1457200","name":null,"product":"thioredoxin 1","uniprot_acc":null,"chromosome":null,"start_pos":null},{"strain":"PbANKA","gene_id":"PBANKA_1320900","name":null,"product":"thioredoxin 1, putative","uniprot_acc":null,"chromosome":null,"start_pos":null},{"strain":"PkH","gene_id":"PKNH_1224600","name":null,"product":"thioredoxin 1, putative","uniprot_acc":null,"chromosome":null,"start_pos":null}],"gene_symbol":"TRX1","evaluation":null}