{"gene":"PF3D7_0303600","run_date":"2026-09-07T10:55:51","timeline":{"discoveries":[{"year":2003,"finding":"Plrx (plasmoredoxin) was identified as a novel 22 kDa redox-active protein unique to malarial parasites. It is a member of the thioredoxin superfamily with a conserved CxxC active-site motif. Purified recombinant Plrx can be reduced by glutathione and more rapidly by dithiols including thioredoxin, glutaredoxin, trypanothione, and tryparedoxin. Reduced Plrx is active in an insulin-reduction assay and reduces glutathione disulfide (rate constant 640 M⁻¹·s⁻¹ at pH 6.9, 25°C). Plrx also provides electrons for ribonucleotide reductase. Glutathione-dependent reduction of H₂O₂ and hydroxyethyl disulfide by Plrx is negligible. The protein is present in blood-stage forms.","method":"Recombinant protein overexpression in E. coli, insulin-reduction assay, kinetic measurements, Western blotting, in silico sequence/phylogenetic analysis","journal":"European journal of biochemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro enzymatic characterization with multiple substrates, kinetic measurements, and functional assays in a single focused study","pmids":["12631266"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2005,"finding":"Plrx was identified as a reducing substrate (electron donor) for P. falciparum thioredoxin peroxidase 1 (TPx1), a 2-Cys peroxiredoxin, in addition to thioredoxin. This establishes Plrx's position in the antioxidant cascade upstream of TPx1.","method":"In vitro enzymatic assay with recombinant proteins; site-directed mutagenesis of TPx1 cysteines; stopped-flow kinetics","journal":"Biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro reconstitution with recombinant proteins and mutagenesis of the acceptor enzyme in a single rigorous study","pmids":["16307478"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2009,"finding":"Using an active-site mutant trap approach (resolving-cysteine mutants bound to affinity columns), 21 potential target proteins of Plrx were identified from P. falciparum cell extracts by mass spectrometry, including proteins involved in protein biosynthesis, energy metabolism, signal transduction, and S-adenosylmethionine (SAM) metabolism.","method":"Affinity chromatography with active-site Cys mutants, DTT elution, mass spectrometry identification of trapped interactors","journal":"PLoS pathogens","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — systematic interactome screen with active-site mutant trapping and MS in a single lab; individual interactions not independently validated for Plrx","pmids":["19360125"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2009,"finding":"Plrx interacts with ornithine aminotransferase (OAT) and S-adenosyl-L-homocysteine hydrolase, as verified by BIAcore surface plasmon resonance binding assays.","method":"BIAcore surface plasmon resonance (SPR)","journal":"PLoS pathogens","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct binding verified by SPR for two substrates in a single lab study","pmids":["19360125"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2011,"finding":"Plrx was identified as a target of protein S-glutathionylation in P. falciparum (i.e., it appears in the glutathionylome). Additionally, Plrx was shown to efficiently catalyze protein deglutathionylation, similarly to P. falciparum glutaredoxin 1 and thioredoxin 1.","method":"Enzymatic deglutathionylation assay, affinity purification of biotin-maleimide-tagged proteins, proteomic analysis","journal":"Antioxidants & redox signaling","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — functional deglutathionylation activity demonstrated in vitro; single lab with two orthogonal methods (proteomics + enzymatic assay)","pmids":["21595565"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2008,"finding":"Disruption of the P. berghei plasmoredoxin gene generated viable knockout parasites that completed full life cycle progression without a detectable phenotype, demonstrating that Plrx is dispensable in vivo in the rodent malaria model.","method":"Gene disruption (knockout) in P. berghei, phenotypic analysis across life cycle stages","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — clean genetic KO with life cycle phenotypic analysis; single lab, rodent model only","pmids":["18575607"],"is_preprint":false,"attribution":[{"species":"Plasmodium berghei","strain":""}]},{"year":2022,"finding":"The 1.6 Å crystal structure of Plrx shows a modified thioredoxin fold with a distinct C-terminal domain and absence of a proline residue within the CxxC redox motif (unlike most thioredoxin superfamily members). Plrx forms monomers and dimers structurally similar to human thioredoxin dimers, and is inactive as a dimer. Monomer-dimer equilibrium depends on redox conditions. The dimer interface carries a cluster of positively charged (lysine) residues absent from other family members, which may mediate binding to cellular membranes or plasminogen.","method":"X-ray crystallography at 1.6 Å resolution; structural analysis of monomer/dimer forms and redox-dependent equilibrium","journal":"Current research in structural biology","confidence":"High","confidence_rationale":"Tier 1 / Moderate — high-resolution crystal structure with structural-functional analysis in a focused single study; activity tied to oligomeric state","pmids":["35434650"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2010,"finding":"Plrx was shown to interact with P. falciparum ornithine δ-aminotransferase (OAT), consistent with its identification as an upstream redox regulator. The interaction was part of a broader study showing that thioredoxin (not Plrx specifically) activates OAT via Cys154 and Cys163; Plrx's role in OAT activation was noted as interaction-level without specific activation kinetics reported for Plrx itself.","method":"Previously established by BIAcore SPR (cross-referenced); crystal structure of OAT; site-directed mutagenesis of OAT cysteines","journal":"Journal of molecular biology","confidence":"Low","confidence_rationale":"Tier 3 / Weak — Plrx-OAT interaction confirmed by cross-reference to prior SPR data; activation of OAT demonstrated only for Trx, not Plrx, in this paper","pmids":["20673832"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]}],"current_model":"Plrx (PF3D7_0303600) is a 22 kDa thiol-disulfide oxidoreductase unique to malarial parasites that adopts a modified thioredoxin fold (solved at 1.6 Å), is reducible by glutathione and dithiol redox proteins, functions as an electron donor for ribonucleotide reductase and the 2-Cys peroxiredoxin TPx1, catalyzes protein deglutathionylation, and engages at least 21 target proteins (including OAT and SAH hydrolase) via its CxxC active site; it is active as a monomer (inactive as a dimer in a redox-sensitive equilibrium) and is dispensable for P. berghei life cycle progression in vivo."},"narrative":{"mechanistic_narrative":"Plrx (PF3D7_0303600, plasmoredoxin) is a 22 kDa thiol-disulfide oxidoreductase unique to malarial parasites that operates within the parasite's cytosolic redox network in blood-stage forms [PMID:12631266]. As a thioredoxin-superfamily member bearing a conserved CxxC active-site motif, reduced Plrx displays classical oxidoreductase activity in the insulin-reduction assay and is regenerated by glutathione and, more efficiently, by the dithiol redox proteins thioredoxin, glutaredoxin, trypanothione, and tryparedoxin [PMID:12631266]. Functionally it serves as an electron donor for ribonucleotide reductase [PMID:12631266] and for the 2-Cys peroxiredoxin TPx1, placing it upstream in the antioxidant cascade [PMID:16307478], and it catalyzes protein deglutathionylation while itself being a substrate of S-glutathionylation [PMID:21595565]. Active-site mutant trapping and SPR define a target set of at least 21 proteins spanning protein biosynthesis, energy metabolism, signal transduction, and SAM metabolism, with direct binding confirmed for ornithine aminotransferase and S-adenosyl-L-homocysteine hydrolase [PMID:19360125]. A 1.6 Å crystal structure reveals a modified thioredoxin fold with a distinct C-terminal domain and a CxxC motif lacking the usual proline; Plrx is catalytically active as a monomer and inactive as a redox-sensitive dimer [PMID:35434650]. Despite these biochemical roles, Plrx is dispensable for life cycle progression in the P. berghei rodent model [PMID:18575607].","teleology":[{"year":2003,"claim":"Establishing whether malarial parasites possess a distinct redox-active enzyme answered what molecular activity Plrx contributes: it defined Plrx as a parasite-specific thioredoxin-family oxidoreductase reducible by both glutathione and dithiols and capable of donating electrons to ribonucleotide reductase.","evidence":"recombinant expression, insulin-reduction and kinetic assays, phylogenetic analysis in P. falciparum","pmids":["12631266"],"confidence":"High","gaps":["Physiological reductant in vivo not resolved among the several capable dithiols","No cellular localization or expression dynamics across stages beyond blood-stage presence"],"attribution":[]},{"year":2005,"claim":"Identifying an electron acceptor placed Plrx within a defined antioxidant pathway rather than as an isolated redox protein: it acts upstream of the 2-Cys peroxiredoxin TPx1.","evidence":"in vitro reconstitution with recombinant proteins plus TPx1 cysteine mutagenesis and stopped-flow kinetics in P. falciparum","pmids":["16307478"],"confidence":"High","gaps":["Relative contribution of Plrx versus thioredoxin as the physiological TPx1 reductant not quantified","In vivo relevance of the Plrx-TPx1 branch untested"],"attribution":[]},{"year":2008,"claim":"Testing genetic requirement addressed whether Plrx's biochemical activities are essential: gene disruption showed it is dispensable for the complete parasite life cycle.","evidence":"targeted gene knockout and life cycle phenotyping in P. berghei","pmids":["18575607"],"confidence":"Medium","gaps":["Rodent model only; P. falciparum requirement untested","Possible functional redundancy with other thioredoxin-family reductases not assessed"],"attribution":[]},{"year":2009,"claim":"Defining a target repertoire answered which cellular processes Plrx acts on: active-site trapping and SPR identified ~21 candidate partners with confirmed binding to OAT and SAH hydrolase, implicating Plrx in biosynthesis, metabolism, and SAM pathways.","evidence":"active-site Cys mutant affinity trapping with mass spectrometry and BIAcore SPR in P. falciparum","pmids":["19360125"],"confidence":"Medium","gaps":["Individual interactions beyond OAT and SAH hydrolase not independently validated","Functional consequence of these interactions (e.g., redox regulation of the targets) not demonstrated"],"attribution":[]},{"year":2010,"claim":"Cross-referencing the OAT interaction probed whether Plrx regulates a specific metabolic enzyme, but OAT activation was demonstrated only for thioredoxin, leaving Plrx's regulatory role at the interaction level.","evidence":"OAT crystal structure and cysteine mutagenesis with cross-referenced SPR data in P. falciparum","pmids":["20673832"],"confidence":"Low","gaps":["No activation kinetics reported for Plrx itself, only for thioredoxin","Whether Plrx modulates OAT activity remains undemonstrated"],"attribution":[]},{"year":2011,"claim":"Characterizing glutathionylation biology clarified a distinct catalytic activity: Plrx catalyzes protein deglutathionylation and is itself a glutathionylation target, linking it to reversible redox modification of the parasite proteome.","evidence":"enzymatic deglutathionylation assay plus glutathionylome proteomics in P. falciparum","pmids":["21595565"],"confidence":"Medium","gaps":["Physiological deglutathionylation substrates not identified","Relative efficiency versus glutaredoxin 1 and thioredoxin 1 in cells not established"],"attribution":[]},{"year":2022,"claim":"Solving the atomic structure connected activity to oligomeric state: Plrx adopts a modified thioredoxin fold with an atypical CxxC motif and is active as a monomer but inactive as a redox-dependent dimer.","evidence":"1.6 Å X-ray crystallography and monomer/dimer structural analysis in P. falciparum","pmids":["35434650"],"confidence":"High","gaps":["Proposed membrane/plasminogen binding via the lysine-rich dimer interface is structurally inferred, not functionally tested","Regulation of the monomer-dimer switch in vivo unknown"],"attribution":[]},{"year":null,"claim":"Whether Plrx's biochemically defined redox activities and target interactions translate into a specific cellular or pathological role in human malaria remains unresolved.","evidence":"no direct evidence in the available corpus","pmids":[],"confidence":"Low","gaps":["No P. falciparum loss-of-function phenotype","Functional significance of the ~21-member target set uncharacterized","In vivo redox partner and physiological electron flow undefined"],"attribution":[]}],"mechanism_profile":{"molecular_activity":[],"localization":[],"pathway":[],"complexes":[],"partners":["TPX1 (2-CYS PEROXIREDOXIN, ELECTRON ACCEPTOR)","RIBONUCLEOTIDE REDUCTASE (ELECTRON ACCEPTOR)","ORNITHINE AMINOTRANSFERASE (OAT)","S-ADENOSYL-L-HOMOCYSTEINE HYDROLASE","THIOREDOXIN, GLUTAREDOXIN, TRYPANOTHIONE, TRYPAREDOXIN (REDUCTANTS)"],"other_free_text":["22 kDa protein unique to malarial parasites with a modified thioredoxin fold and CxxC active-site motif lacking the conserved proline [#0, #6]","Active as a monomer, inactive as a redox-sensitive dimer; dimer interface carries a lysine-rich cluster [#6]","At least 21 candidate target proteins identified by active-site mutant trapping [#2]","Dispensable for the P. berghei life cycle [#5]"]}},"prefetch_data":{},"corpus_meta":[{"pmid":"22939033","id":"PMC_22939033","title":"Thioredoxin and glutathione systems in Plasmodium falciparum.","date":"2012","source":"International journal of medical microbiology : IJMM","url":"https://pubmed.ncbi.nlm.nih.gov/22939033","citation_count":100,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["plasmoredoxin"],"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 signaling","url":"https://pubmed.ncbi.nlm.nih.gov/21595565","citation_count":87,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["plasmoredoxin"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"17012768","id":"PMC_17012768","title":"The thiol-based redox networks of pathogens: unexploited targets in the search for new drugs.","date":"2006","source":"BioFactors (Oxford, England)","url":"https://pubmed.ncbi.nlm.nih.gov/17012768","citation_count":73,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["plasmoredoxin"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"19360125","id":"PMC_19360125","title":"Identification of proteins targeted by the thioredoxin superfamily in Plasmodium falciparum.","date":"2009","source":"PLoS pathogens","url":"https://pubmed.ncbi.nlm.nih.gov/19360125","citation_count":69,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["Plrx","plasmoredoxin"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"12631266","id":"PMC_12631266","title":"Plasmoredoxin, a novel redox-active protein unique for malarial parasites.","date":"2003","source":"European journal of biochemistry","url":"https://pubmed.ncbi.nlm.nih.gov/12631266","citation_count":39,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["Plrx","plasmoredoxin"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"20673832","id":"PMC_20673832","title":"Redox regulation of Plasmodium falciparum ornithine δ-aminotransferase.","date":"2010","source":"Journal of molecular biology","url":"https://pubmed.ncbi.nlm.nih.gov/20673832","citation_count":31,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["plasmoredoxin"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"16307478","id":"PMC_16307478","title":"Plasmodium falciparum 2-Cys peroxiredoxin reacts with plasmoredoxin and peroxynitrite.","date":"2005","source":"Biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/16307478","citation_count":30,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["plasmoredoxin"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"14962358","id":"PMC_14962358","title":"Plasmodium falciparum thioredoxins and glutaredoxins as central players in redox metabolism.","date":"2003","source":"Redox report : communications in free radical research","url":"https://pubmed.ncbi.nlm.nih.gov/14962358","citation_count":29,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["plasmoredoxin"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"18575607","id":"PMC_18575607","title":"Depletion of Plasmodium berghei plasmoredoxin reveals a non-essential role for life cycle progression of the malaria parasite.","date":"2008","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/18575607","citation_count":11,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["plasmoredoxin"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"35434650","id":"PMC_35434650","title":"Crystal structure of plasmoredoxin, a redox-active protein unique for malaria parasites.","date":"2022","source":"Current research in structural biology","url":"https://pubmed.ncbi.nlm.nih.gov/35434650","citation_count":1,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["Plrx","plasmoredoxin"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":8112,"output_tokens":2419,"usd":0.030311,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":7742,"output_tokens":3035,"usd":0.057293,"stage2_stop_reason":"end_turn"},"total_usd":0.087604,"stage1_batch_id":"msgbatch_01DbiymDmubkPpYvdbAu5a7V","stage2_batch_id":"msgbatch_012TbrWvMRH129T7PQ4SmvrJ","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2003,\n      \"finding\": \"Plrx (plasmoredoxin) was identified as a novel 22 kDa redox-active protein unique to malarial parasites. It is a member of the thioredoxin superfamily with a conserved CxxC active-site motif. Purified recombinant Plrx can be reduced by glutathione and more rapidly by dithiols including thioredoxin, glutaredoxin, trypanothione, and tryparedoxin. Reduced Plrx is active in an insulin-reduction assay and reduces glutathione disulfide (rate constant 640 M⁻¹·s⁻¹ at pH 6.9, 25°C). Plrx also provides electrons for ribonucleotide reductase. Glutathione-dependent reduction of H₂O₂ and hydroxyethyl disulfide by Plrx is negligible. The protein is present in blood-stage forms.\",\n      \"method\": \"Recombinant protein overexpression in E. coli, insulin-reduction assay, kinetic measurements, Western blotting, in silico sequence/phylogenetic analysis\",\n      \"journal\": \"European journal of biochemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro enzymatic characterization with multiple substrates, kinetic measurements, and functional assays in a single focused study\",\n      \"pmids\": [\"12631266\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Plrx was identified as a reducing substrate (electron donor) for P. falciparum thioredoxin peroxidase 1 (TPx1), a 2-Cys peroxiredoxin, in addition to thioredoxin. This establishes Plrx's position in the antioxidant cascade upstream of TPx1.\",\n      \"method\": \"In vitro enzymatic assay with recombinant proteins; site-directed mutagenesis of TPx1 cysteines; stopped-flow kinetics\",\n      \"journal\": \"Biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro reconstitution with recombinant proteins and mutagenesis of the acceptor enzyme in a single rigorous study\",\n      \"pmids\": [\"16307478\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Using an active-site mutant trap approach (resolving-cysteine mutants bound to affinity columns), 21 potential target proteins of Plrx were identified from P. falciparum cell extracts by mass spectrometry, including proteins involved in protein biosynthesis, energy metabolism, signal transduction, and S-adenosylmethionine (SAM) metabolism.\",\n      \"method\": \"Affinity chromatography with active-site Cys mutants, DTT elution, mass spectrometry identification of trapped interactors\",\n      \"journal\": \"PLoS pathogens\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — systematic interactome screen with active-site mutant trapping and MS in a single lab; individual interactions not independently validated for Plrx\",\n      \"pmids\": [\"19360125\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Plrx interacts with ornithine aminotransferase (OAT) and S-adenosyl-L-homocysteine hydrolase, as verified by BIAcore surface plasmon resonance binding assays.\",\n      \"method\": \"BIAcore surface plasmon resonance (SPR)\",\n      \"journal\": \"PLoS pathogens\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct binding verified by SPR for two substrates in a single lab study\",\n      \"pmids\": [\"19360125\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Plrx was identified as a target of protein S-glutathionylation in P. falciparum (i.e., it appears in the glutathionylome). Additionally, Plrx was shown to efficiently catalyze protein deglutathionylation, similarly to P. falciparum glutaredoxin 1 and thioredoxin 1.\",\n      \"method\": \"Enzymatic deglutathionylation assay, affinity purification of biotin-maleimide-tagged proteins, proteomic analysis\",\n      \"journal\": \"Antioxidants & redox signaling\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional deglutathionylation activity demonstrated in vitro; single lab with two orthogonal methods (proteomics + enzymatic assay)\",\n      \"pmids\": [\"21595565\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"Disruption of the P. berghei plasmoredoxin gene generated viable knockout parasites that completed full life cycle progression without a detectable phenotype, demonstrating that Plrx is dispensable in vivo in the rodent malaria model.\",\n      \"method\": \"Gene disruption (knockout) in P. berghei, phenotypic analysis across life cycle stages\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — clean genetic KO with life cycle phenotypic analysis; single lab, rodent model only\",\n      \"pmids\": [\"18575607\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium berghei\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"The 1.6 Å crystal structure of Plrx shows a modified thioredoxin fold with a distinct C-terminal domain and absence of a proline residue within the CxxC redox motif (unlike most thioredoxin superfamily members). Plrx forms monomers and dimers structurally similar to human thioredoxin dimers, and is inactive as a dimer. Monomer-dimer equilibrium depends on redox conditions. The dimer interface carries a cluster of positively charged (lysine) residues absent from other family members, which may mediate binding to cellular membranes or plasminogen.\",\n      \"method\": \"X-ray crystallography at 1.6 Å resolution; structural analysis of monomer/dimer forms and redox-dependent equilibrium\",\n      \"journal\": \"Current research in structural biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — high-resolution crystal structure with structural-functional analysis in a focused single study; activity tied to oligomeric state\",\n      \"pmids\": [\"35434650\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"Plrx was shown to interact with P. falciparum ornithine δ-aminotransferase (OAT), consistent with its identification as an upstream redox regulator. The interaction was part of a broader study showing that thioredoxin (not Plrx specifically) activates OAT via Cys154 and Cys163; Plrx's role in OAT activation was noted as interaction-level without specific activation kinetics reported for Plrx itself.\",\n      \"method\": \"Previously established by BIAcore SPR (cross-referenced); crystal structure of OAT; site-directed mutagenesis of OAT cysteines\",\n      \"journal\": \"Journal of molecular biology\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — Plrx-OAT interaction confirmed by cross-reference to prior SPR data; activation of OAT demonstrated only for Trx, not Plrx, in this paper\",\n      \"pmids\": [\"20673832\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    }\n  ],\n  \"current_model\": \"Plrx (PF3D7_0303600) is a 22 kDa thiol-disulfide oxidoreductase unique to malarial parasites that adopts a modified thioredoxin fold (solved at 1.6 Å), is reducible by glutathione and dithiol redox proteins, functions as an electron donor for ribonucleotide reductase and the 2-Cys peroxiredoxin TPx1, catalyzes protein deglutathionylation, and engages at least 21 target proteins (including OAT and SAH hydrolase) via its CxxC active site; it is active as a monomer (inactive as a dimer in a redox-sensitive equilibrium) and is dispensable for P. berghei life cycle progression in vivo.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"Plrx (PF3D7_0303600, plasmoredoxin) is a 22 kDa thiol-disulfide oxidoreductase unique to malarial parasites that operates within the parasite's cytosolic redox network in blood-stage forms [#0]. As a thioredoxin-superfamily member bearing a conserved CxxC active-site motif, reduced Plrx displays classical oxidoreductase activity in the insulin-reduction assay and is regenerated by glutathione and, more efficiently, by the dithiol redox proteins thioredoxin, glutaredoxin, trypanothione, and tryparedoxin [#0]. Functionally it serves as an electron donor for ribonucleotide reductase [#0] and for the 2-Cys peroxiredoxin TPx1, placing it upstream in the antioxidant cascade [#1], and it catalyzes protein deglutathionylation while itself being a substrate of S-glutathionylation [#4]. Active-site mutant trapping and SPR define a target set of at least 21 proteins spanning protein biosynthesis, energy metabolism, signal transduction, and SAM metabolism, with direct binding confirmed for ornithine aminotransferase and S-adenosyl-L-homocysteine hydrolase [#2, #3]. A 1.6 Å crystal structure reveals a modified thioredoxin fold with a distinct C-terminal domain and a CxxC motif lacking the usual proline; Plrx is catalytically active as a monomer and inactive as a redox-sensitive dimer [#6]. Despite these biochemical roles, Plrx is dispensable for life cycle progression in the P. berghei rodent model [#5].\",\n  \"teleology\": [\n    {\n      \"year\": 2003,\n      \"claim\": \"Establishing whether malarial parasites possess a distinct redox-active enzyme answered what molecular activity Plrx contributes: it defined Plrx as a parasite-specific thioredoxin-family oxidoreductase reducible by both glutathione and dithiols and capable of donating electrons to ribonucleotide reductase.\",\n      \"evidence\": \"recombinant expression, insulin-reduction and kinetic assays, phylogenetic analysis in P. falciparum\",\n      \"pmids\": [\"12631266\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Physiological reductant in vivo not resolved among the several capable dithiols\", \"No cellular localization or expression dynamics across stages beyond blood-stage presence\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Identifying an electron acceptor placed Plrx within a defined antioxidant pathway rather than as an isolated redox protein: it acts upstream of the 2-Cys peroxiredoxin TPx1.\",\n      \"evidence\": \"in vitro reconstitution with recombinant proteins plus TPx1 cysteine mutagenesis and stopped-flow kinetics in P. falciparum\",\n      \"pmids\": [\"16307478\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Relative contribution of Plrx versus thioredoxin as the physiological TPx1 reductant not quantified\", \"In vivo relevance of the Plrx-TPx1 branch untested\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Testing genetic requirement addressed whether Plrx's biochemical activities are essential: gene disruption showed it is dispensable for the complete parasite life cycle.\",\n      \"evidence\": \"targeted gene knockout and life cycle phenotyping in P. berghei\",\n      \"pmids\": [\"18575607\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Rodent model only; P. falciparum requirement untested\", \"Possible functional redundancy with other thioredoxin-family reductases not assessed\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Defining a target repertoire answered which cellular processes Plrx acts on: active-site trapping and SPR identified ~21 candidate partners with confirmed binding to OAT and SAH hydrolase, implicating Plrx in biosynthesis, metabolism, and SAM pathways.\",\n      \"evidence\": \"active-site Cys mutant affinity trapping with mass spectrometry and BIAcore SPR in P. falciparum\",\n      \"pmids\": [\"19360125\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Individual interactions beyond OAT and SAH hydrolase not independently validated\", \"Functional consequence of these interactions (e.g., redox regulation of the targets) not demonstrated\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Cross-referencing the OAT interaction probed whether Plrx regulates a specific metabolic enzyme, but OAT activation was demonstrated only for thioredoxin, leaving Plrx's regulatory role at the interaction level.\",\n      \"evidence\": \"OAT crystal structure and cysteine mutagenesis with cross-referenced SPR data in P. falciparum\",\n      \"pmids\": [\"20673832\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No activation kinetics reported for Plrx itself, only for thioredoxin\", \"Whether Plrx modulates OAT activity remains undemonstrated\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Characterizing glutathionylation biology clarified a distinct catalytic activity: Plrx catalyzes protein deglutathionylation and is itself a glutathionylation target, linking it to reversible redox modification of the parasite proteome.\",\n      \"evidence\": \"enzymatic deglutathionylation assay plus glutathionylome proteomics in P. falciparum\",\n      \"pmids\": [\"21595565\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Physiological deglutathionylation substrates not identified\", \"Relative efficiency versus glutaredoxin 1 and thioredoxin 1 in cells not established\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Solving the atomic structure connected activity to oligomeric state: Plrx adopts a modified thioredoxin fold with an atypical CxxC motif and is active as a monomer but inactive as a redox-dependent dimer.\",\n      \"evidence\": \"1.6 Å X-ray crystallography and monomer/dimer structural analysis in P. falciparum\",\n      \"pmids\": [\"35434650\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Proposed membrane/plasminogen binding via the lysine-rich dimer interface is structurally inferred, not functionally tested\", \"Regulation of the monomer-dimer switch in vivo unknown\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Whether Plrx's biochemically defined redox activities and target interactions translate into a specific cellular or pathological role in human malaria remains unresolved.\",\n      \"evidence\": \"no direct evidence in the available corpus\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No P. falciparum loss-of-function phenotype\", \"Functional significance of the ~21-member target set uncharacterized\", \"In vivo redox partner and physiological electron flow undefined\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0015035\", \"supporting_discovery_ids\": [0, 1]},\n      {\"term_id\": \"GO:0045454\", \"supporting_discovery_ids\": [0, 1]},\n      {\"term_id\": \"GO:0080043\", \"supporting_discovery_ids\": [4]},\n      {\"term_id\": \"GO:0005515\", \"supporting_discovery_ids\": [2, 3]}\n    ],\n    \"localization\": [],\n    \"pathway\": [\n      {\"term_id\": \"GO:0006979\", \"supporting_discovery_ids\": [1]},\n      {\"term_id\": \"GO:0009263\", \"supporting_discovery_ids\": [0]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\n      \"TPx1 (2-Cys peroxiredoxin, electron acceptor)\",\n      \"ribonucleotide reductase (electron acceptor)\",\n      \"ornithine aminotransferase (OAT)\",\n      \"S-adenosyl-L-homocysteine hydrolase\",\n      \"thioredoxin, glutaredoxin, trypanothione, tryparedoxin (reductants)\"\n    ],\n    \"other_free_text\": [\n      \"22 kDa protein unique to malarial parasites with a modified thioredoxin fold and CxxC active-site motif lacking the conserved proline [#0, #6]\",\n      \"Active as a monomer, inactive as a redox-sensitive dimer; dimer interface carries a lysine-rich cluster [#6]\",\n      \"At least 21 candidate target proteins identified by active-site mutant trapping [#2]\",\n      \"Dispensable for the P. berghei life cycle [#5]\"\n    ]\n  }\n}","audit_flag":null,"strains":[{"strain":"Pf3D7","gene_id":"PF3D7_0303600","name":null,"product":"plasmoredoxin","uniprot_acc":null,"chromosome":null,"start_pos":null},{"strain":"PbANKA","gene_id":"PBANKA_0402200","name":null,"product":"plasmoredoxin","uniprot_acc":null,"chromosome":null,"start_pos":null},{"strain":"PkH","gene_id":"PKNH_0839500","name":null,"product":"thioredoxin-like redox-active protein, putative","uniprot_acc":null,"chromosome":null,"start_pos":null}],"gene_symbol":"Plrx","evaluation":null}