{"gene":"TG_266130","gene_symbol":"PRX2","run_date":"2026-09-08T14:08:29","timeline":{"discoveries":[{"year":2004,"finding":"TgPrx2 is a cytosolic 1-cys peroxiredoxin in Toxoplasma gondii; overexpression of TgPrx2 increases protection against H2O2 treatment, establishing its role as a peroxidase contributing to defence against oxidative stress.","method":"Gene overexpression under strong promoter; H2O2 challenge assay","journal":"Molecular microbiology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — overexpression with defined phenotypic readout (H2O2 protection), subcellular localization established, single lab but two orthogonal approaches (OE + localization)","pmids":["14651610"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2005,"finding":"TgPrx2 acts via a 2-Cys mechanism despite being classified as a 1-Cys peroxiredoxin: Cys47 is the active-site (peroxidatic) cysteine, and it forms an intermolecular disulfide with Cys209 from the C-terminal domain of a second subunit (resolving cysteine), analogous to typical 2-Cys peroxiredoxins. TgPrx2 does not reduce H2O2 or tBHP at the expense of glutaredoxin, thioredoxin, or glutathione. It forms tetramers and hexamers but does not oligomerize to decamers. It has general antioxidant properties (protection of glutamine synthetase against DTT/Fe3+-catalyzed oxidation).","method":"Site-directed mutagenesis of Cys47 and Cys209; gel filtration chromatography; in vitro peroxidase activity assays with glutaredoxin, thioredoxin, glutathione; glutamine synthetase protection assay; molecular modeling","journal":"Molecular and biochemical parasitology","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro reconstitution with mutagenesis (active-site identification), multiple orthogonal biochemical assays, single lab","pmids":["15694490"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2025,"finding":"TgPRX2 is not individually required for the lytic cycle under standard growth conditions, but combined deletion of TgPRX1 and TgPRX2 causes notable impairment of parasite growth, indicating functional redundancy between the two cytosolic peroxidases.","method":"Genetic knockout (single and double deletion mutants); lytic cycle/growth assay; hydrogen peroxide susceptibility assay","journal":"FASEB journal","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — clean KO with defined cellular phenotype, double-mutant epistasis reveals redundancy, single lab","pmids":["40059453"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2025,"finding":"TgPRX2 is downregulated in extracellular tachyzoites upon direct exposure to GPX4 inhibitor RSL3, associated with increased lipid ROS and growth arrest, indicating that TgPRX2 contributes to parasite redox homeostasis during oxidative stress.","method":"Pharmacological treatment (RSL3); transcriptomic analysis; ROS measurement","journal":"Virulence","confidence":"Low","confidence_rationale":"Tier 3 / Weak — transcriptomics-based observation after drug treatment, single lab, indirect link to TgPRX2 function","pmids":["40667873"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]}],"current_model":"TgPRX2 is a cytosolic peroxiredoxin in Toxoplasma gondii that, despite its classification as a 1-Cys Prx, employs a 2-Cys mechanism in which the active-site Cys47 forms an intermolecular disulfide with the resolving Cys209 of a second subunit; it provides redundant protection against oxidative stress alongside TgPRX1, with combined loss of both leading to impaired parasite growth, while neither enzyme is individually essential for the lytic cycle under standard conditions."},"narrative":{"mechanistic_narrative":"TgPRX2 is a cytosolic peroxiredoxin in Toxoplasma gondii that contributes to antioxidant defence during oxidative stress [PMID:14651610]. Although classified as a 1-Cys peroxiredoxin, it operates through a 2-Cys mechanism in which the active-site (peroxidatic) Cys47 forms an intermolecular disulfide with the resolving Cys209 from the C-terminal domain of a second subunit; the enzyme assembles into tetramers and hexamers but not decamers, and reduces peroxides without dependence on glutaredoxin, thioredoxin, or glutathione while also affording general antioxidant protection to substrate proteins [PMID:15694490]. Functionally, TgPRX2 is not individually required for the lytic cycle under standard conditions, but acts redundantly with the cytosolic peroxidase TgPRX1, since combined deletion of both markedly impairs parasite growth [PMID:40059453].","teleology":[{"year":2004,"claim":"Establishing that a cytosolic Toxoplasma peroxiredoxin functions in oxidative defence answered whether the parasite deploys dedicated peroxidases against host- and self-derived oxidants.","evidence":"Overexpression under a strong promoter with H2O2 challenge and subcellular localization in T. gondii","pmids":["14651610"],"confidence":"Medium","gaps":["Overexpression phenotype does not establish the endogenous requirement for the gene","The catalytic mechanism and physiological electron donor were not defined"],"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2005,"claim":"Defining the catalytic residues resolved the paradox of a 1-Cys-classified enzyme by showing it uses a 2-Cys intermolecular disulfide mechanism and clarified its oligomeric state and independence from canonical thiol donors.","evidence":"Site-directed mutagenesis of Cys47/Cys209, gel filtration, in vitro peroxidase and glutamine synthetase protection assays, and molecular modeling","pmids":["15694490"],"confidence":"High","gaps":["The physiological reductant that recycles the disulfide was not identified","In vitro assays do not establish the in vivo substrate spectrum"],"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2025,"claim":"Genetic knockout answered whether TgPRX2 is essential, revealing dispensability alone but functional redundancy with TgPRX1 in supporting parasite growth.","evidence":"Single and double deletion mutants with lytic cycle/growth and H2O2 susceptibility assays in T. gondii","pmids":["40059453"],"confidence":"Medium","gaps":["Molecular basis of redundancy (shared substrates vs. parallel pathways) not resolved","Growth impairment not linked to a specific oxidative or metabolic defect"],"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2025,"claim":"Pharmacological perturbation of lipid peroxide defence linked TgPRX2 expression to redox homeostasis during induced oxidative stress.","evidence":"RSL3 (GPX4 inhibitor) treatment with transcriptomics and ROS measurement in extracellular tachyzoites","pmids":["40667873"],"confidence":"Low","gaps":["Transcriptomic downregulation is an indirect readout and does not establish a functional role for TgPRX2 in this response","Causal contribution of TgPRX2 to lipid ROS control was not tested genetically"],"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":null,"claim":"The physiological electron donor that recycles the TgPRX2 disulfide and the mechanistic basis of its redundancy with TgPRX1 remain unresolved.","evidence":"","pmids":[],"confidence":"Low","gaps":["No in vivo reductant identified","No structural model of the active oligomer under reducing conditions","Substrate overlap with TgPRX1 not directly mapped"],"attribution":[{"species":"Toxoplasma gondii","strain":""}]}],"mechanism_profile":{"molecular_activity":[],"localization":[],"pathway":[],"complexes":["Homo-oligomers (tetramers and hexamers) formed via intermolecular Cys47-Cys209 disulfide"],"partners":["TGPRX1 (FUNCTIONALLY REDUNDANT CYTOSOLIC PEROXIDASE)"],"other_free_text":["Uses a 2-Cys catalytic mechanism (peroxidatic Cys47, resolving Cys209) despite 1-Cys classification","Does not use glutaredoxin, thioredoxin, or glutathione as electron donors in vitro","Provides general antioxidant protection (glutamine synthetase against DTT/Fe3+-catalyzed oxidation)","Individually dispensable for the lytic cycle under standard conditions"]},"strain_conflicts":[]},"prefetch_data":{},"corpus_meta":[{"pmid":"14651610","id":"PMC_14651610","title":"The antioxidant systems in Toxoplasma gondii and the role of cytosolic catalase in defence against oxidative injury.","date":"2004","source":"Molecular microbiology","url":"https://pubmed.ncbi.nlm.nih.gov/14651610","citation_count":105,"is_preprint":false},{"pmid":"15694490","id":"PMC_15694490","title":"Biochemical characterization of Toxoplasma gondii 1-Cys peroxiredoxin 2 with mechanistic similarities to typical 2-Cys Prx.","date":"2005","source":"Molecular and biochemical parasitology","url":"https://pubmed.ncbi.nlm.nih.gov/15694490","citation_count":39,"is_preprint":false},{"pmid":"40667873","id":"PMC_40667873","title":"Ferroptosis is important for Toxoplasma gondii replication and virulence in vitro and in vivo.","date":"2025","source":"Virulence","url":"https://pubmed.ncbi.nlm.nih.gov/40667873","citation_count":4,"is_preprint":false},{"pmid":"40059453","id":"PMC_40059453","title":"Toxoplasma survives the loss of key enzymes of peroxide and glutathione metabolism.","date":"2025","source":"FASEB journal : official publication of the Federation of American Societies for Experimental Biology","url":"https://pubmed.ncbi.nlm.nih.gov/40059453","citation_count":1,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":4633,"output_tokens":1244,"usd":0.016279,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":6193,"output_tokens":2353,"usd":0.044895,"stage2_stop_reason":"end_turn"},"total_usd":0.061174,"stage1_batch_id":"msgbatch_015xmQKDRqnTh9anE4m7LiD6","stage2_batch_id":"msgbatch_01JLpkFTVhoQBNgqHCKFrVVU","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2004,\n      \"finding\": \"TgPrx2 is a cytosolic 1-cys peroxiredoxin in Toxoplasma gondii; overexpression of TgPrx2 increases protection against H2O2 treatment, establishing its role as a peroxidase contributing to defence against oxidative stress.\",\n      \"method\": \"Gene overexpression under strong promoter; H2O2 challenge assay\",\n      \"journal\": \"Molecular microbiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — overexpression with defined phenotypic readout (H2O2 protection), subcellular localization established, single lab but two orthogonal approaches (OE + localization)\",\n      \"pmids\": [\"14651610\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"TgPrx2 acts via a 2-Cys mechanism despite being classified as a 1-Cys peroxiredoxin: Cys47 is the active-site (peroxidatic) cysteine, and it forms an intermolecular disulfide with Cys209 from the C-terminal domain of a second subunit (resolving cysteine), analogous to typical 2-Cys peroxiredoxins. TgPrx2 does not reduce H2O2 or tBHP at the expense of glutaredoxin, thioredoxin, or glutathione. It forms tetramers and hexamers but does not oligomerize to decamers. It has general antioxidant properties (protection of glutamine synthetase against DTT/Fe3+-catalyzed oxidation).\",\n      \"method\": \"Site-directed mutagenesis of Cys47 and Cys209; gel filtration chromatography; in vitro peroxidase activity assays with glutaredoxin, thioredoxin, glutathione; glutamine synthetase protection assay; molecular modeling\",\n      \"journal\": \"Molecular and biochemical parasitology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro reconstitution with mutagenesis (active-site identification), multiple orthogonal biochemical assays, single lab\",\n      \"pmids\": [\"15694490\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"TgPRX2 is not individually required for the lytic cycle under standard growth conditions, but combined deletion of TgPRX1 and TgPRX2 causes notable impairment of parasite growth, indicating functional redundancy between the two cytosolic peroxidases.\",\n      \"method\": \"Genetic knockout (single and double deletion mutants); lytic cycle/growth assay; hydrogen peroxide susceptibility assay\",\n      \"journal\": \"FASEB journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — clean KO with defined cellular phenotype, double-mutant epistasis reveals redundancy, single lab\",\n      \"pmids\": [\"40059453\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"TgPRX2 is downregulated in extracellular tachyzoites upon direct exposure to GPX4 inhibitor RSL3, associated with increased lipid ROS and growth arrest, indicating that TgPRX2 contributes to parasite redox homeostasis during oxidative stress.\",\n      \"method\": \"Pharmacological treatment (RSL3); transcriptomic analysis; ROS measurement\",\n      \"journal\": \"Virulence\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — transcriptomics-based observation after drug treatment, single lab, indirect link to TgPRX2 function\",\n      \"pmids\": [\"40667873\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    }\n  ],\n  \"current_model\": \"TgPRX2 is a cytosolic peroxiredoxin in Toxoplasma gondii that, despite its classification as a 1-Cys Prx, employs a 2-Cys mechanism in which the active-site Cys47 forms an intermolecular disulfide with the resolving Cys209 of a second subunit; it provides redundant protection against oxidative stress alongside TgPRX1, with combined loss of both leading to impaired parasite growth, while neither enzyme is individually essential for the lytic cycle under standard conditions.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"TgPRX2 is a cytosolic peroxiredoxin in Toxoplasma gondii that contributes to antioxidant defence during oxidative stress [#0]. Although classified as a 1-Cys peroxiredoxin, it operates through a 2-Cys mechanism in which the active-site (peroxidatic) Cys47 forms an intermolecular disulfide with the resolving Cys209 from the C-terminal domain of a second subunit; the enzyme assembles into tetramers and hexamers but not decamers, and reduces peroxides without dependence on glutaredoxin, thioredoxin, or glutathione while also affording general antioxidant protection to substrate proteins [#1]. Functionally, TgPRX2 is not individually required for the lytic cycle under standard conditions, but acts redundantly with the cytosolic peroxidase TgPRX1, since combined deletion of both markedly impairs parasite growth [#2].\",\n  \"teleology\": [\n    {\n      \"year\": 2004,\n      \"claim\": \"Establishing that a cytosolic Toxoplasma peroxiredoxin functions in oxidative defence answered whether the parasite deploys dedicated peroxidases against host- and self-derived oxidants.\",\n      \"evidence\": \"Overexpression under a strong promoter with H2O2 challenge and subcellular localization in T. gondii\",\n      \"pmids\": [\"14651610\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Overexpression phenotype does not establish the endogenous requirement for the gene\",\n        \"The catalytic mechanism and physiological electron donor were not defined\"\n      ],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Defining the catalytic residues resolved the paradox of a 1-Cys-classified enzyme by showing it uses a 2-Cys intermolecular disulfide mechanism and clarified its oligomeric state and independence from canonical thiol donors.\",\n      \"evidence\": \"Site-directed mutagenesis of Cys47/Cys209, gel filtration, in vitro peroxidase and glutamine synthetase protection assays, and molecular modeling\",\n      \"pmids\": [\"15694490\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"The physiological reductant that recycles the disulfide was not identified\",\n        \"In vitro assays do not establish the in vivo substrate spectrum\"\n      ],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Genetic knockout answered whether TgPRX2 is essential, revealing dispensability alone but functional redundancy with TgPRX1 in supporting parasite growth.\",\n      \"evidence\": \"Single and double deletion mutants with lytic cycle/growth and H2O2 susceptibility assays in T. gondii\",\n      \"pmids\": [\"40059453\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Molecular basis of redundancy (shared substrates vs. parallel pathways) not resolved\",\n        \"Growth impairment not linked to a specific oxidative or metabolic defect\"\n      ],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Pharmacological perturbation of lipid peroxide defence linked TgPRX2 expression to redox homeostasis during induced oxidative stress.\",\n      \"evidence\": \"RSL3 (GPX4 inhibitor) treatment with transcriptomics and ROS measurement in extracellular tachyzoites\",\n      \"pmids\": [\"40667873\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\n        \"Transcriptomic downregulation is an indirect readout and does not establish a functional role for TgPRX2 in this response\",\n        \"Causal contribution of TgPRX2 to lipid ROS control was not tested genetically\"\n      ],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The physiological electron donor that recycles the TgPRX2 disulfide and the mechanistic basis of its redundancy with TgPRX1 remain unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\n        \"No in vivo reductant identified\",\n        \"No structural model of the active oligomer under reducing conditions\",\n        \"Substrate overlap with TgPRX1 not directly mapped\"\n      ],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0051920\", \"supporting_discovery_ids\": [0, 1], \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]},\n      {\"term_id\": \"GO:0004601\", \"supporting_discovery_ids\": [0, 1], \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]},\n      {\"term_id\": \"GO:0016209\", \"supporting_discovery_ids\": [1], \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [0], \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"GO:0006979\", \"supporting_discovery_ids\": [0, 2, 3], \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]},\n      {\"term_id\": \"GO:0045454\", \"supporting_discovery_ids\": [1, 3], \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]}\n    ],\n    \"complexes\": [\n      \"Homo-oligomers (tetramers and hexamers) formed via intermolecular Cys47-Cys209 disulfide\"\n    ],\n    \"partners\": [\n      \"TgPRX1 (functionally redundant cytosolic peroxidase)\"\n    ],\n    \"other_free_text\": [\n      \"Uses a 2-Cys catalytic mechanism (peroxidatic Cys47, resolving Cys209) despite 1-Cys classification\",\n      \"Does not use glutaredoxin, thioredoxin, or glutathione as electron donors in vitro\",\n      \"Provides general antioxidant protection (glutamine synthetase against DTT/Fe3+-catalyzed oxidation)\",\n      \"Individually dispensable for the lytic cycle under standard conditions\"\n    ]\n  },\n  \"strain_conflicts\": []\n}","audit_flag":null,"strains":[{"strain":"ME49","gene_id":"TGME49_266130","name":"PRX2","product":"peroxiredoxin PRX2","uniprot_acc":"A0A125YL97","chromosome":"TGME49_chrIX","start_pos":1280702},{"strain":"GT1","gene_id":"TGGT1_266130","name":null,"product":"peroxiredoxin PRX2","uniprot_acc":null,"chromosome":"TGGT1_chrIX","start_pos":1103897},{"strain":"RH88","gene_id":"TGRH88_011660","name":null,"product":"peroxiredoxin PRX2","uniprot_acc":null,"chromosome":"CM023090","start_pos":1338114},{"strain":"VEG","gene_id":"TGVEG_266130","name":null,"product":"peroxiredoxin PRX2","uniprot_acc":"B6KLW2","chromosome":"TGVEG_chrIX","start_pos":1310315}]}