{"gene":"TG_208010","gene_symbol":"STX19","run_date":"2026-09-08T11:06:18","timeline":{"discoveries":[{"year":2021,"finding":"TgStx19 is a novel Qc-SNARE localized to the endoplasmic reticulum (ER) in Toxoplasma gondii, where it acts as a binding partner of TgStx18, replacing the canonical Use1 partner found in other eukaryotes.","method":"Fluorescence localization experiments and conditional ablation (conditional knockout) with phenotypic analysis of secretory system defects","journal":"mBio","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct localization by imaging and conditional KO with defined secretory phenotype, single lab, two orthogonal methods","pmids":["34340555"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2021,"finding":"Conditional ablation of TgStx19 (an ER-residing SNARE) caused severe defects in the secretory system, establishing its functional requirement for vesicular trafficking through the ER in Toxoplasma gondii.","method":"Conditional knockout with phenotypic analysis of secretory pathway defects","journal":"mBio","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — clean conditional KO with defined cellular phenotype, single lab, single method reported in abstract","pmids":["34340555"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]}],"current_model":"TgStx19 is a novel Qc-SNARE that localizes to the endoplasmic reticulum in Toxoplasma gondii, where it functions as a partner of TgStx18 (replacing the canonical Use1) to mediate vesicular trafficking through the secretory system; its conditional ablation causes severe secretory defects."},"narrative":{"mechanistic_narrative":"In Toxoplasma gondii, STX19 (TgStx19) is a novel Qc-SNARE that resides in the endoplasmic reticulum and functions in vesicular trafficking through the secretory system [PMID:34340555]. It acts as a binding partner of TgStx18, substituting for the canonical Use1 partner found in other eukaryotes [PMID:34340555]. Conditional ablation of TgStx19 causes severe defects in the secretory system, establishing its functional requirement for ER-based trafficking [PMID:34340555]. Beyond these findings, no further mechanistic detail on TgStx19 has been characterized in the available corpus.","teleology":[{"year":2021,"claim":"It was unknown how the ER SNARE machinery is organized in Toxoplasma; imaging and conditional knockout established that TgStx19 is an ER-localized Qc-SNARE that partners with TgStx18 in place of the canonical Use1, defining a divergent SNARE architecture in this parasite.","evidence":"Fluorescence localization and conditional knockout with phenotypic analysis in Toxoplasma gondii","pmids":["34340555"],"confidence":"Medium","gaps":["Direct biochemical demonstration of the TgStx19-TgStx18 SNARE complex and its full R-SNARE/Qa/Qb composition is not established","The specific trafficking step and cargoes dependent on TgStx19 are not defined"],"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2021,"claim":"Whether TgStx19 is functionally required was unknown; conditional ablation producing severe secretory-system defects established that TgStx19 is necessary for vesicular trafficking through the ER.","evidence":"Conditional knockout with phenotypic analysis of secretory pathway defects in Toxoplasma gondii","pmids":["34340555"],"confidence":"Medium","gaps":["The molecular basis linking loss of TgStx19 to the secretory defect (fusion failure, mislocalization of partners) is not resolved","Impact on parasite viability, invasion, or virulence is not delineated in this corpus"],"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":null,"claim":"The structural basis of TgStx19 SNARE-complex assembly, its complete set of interacting SNAREs, and the precise trafficking step it mediates remain undetermined.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No structural or reconstituted-fusion characterization of the TgStx19 complex","No mapping of the exact ER trafficking substep or cargo dependence"],"attribution":[{"species":"Toxoplasma gondii","strain":""}]}],"mechanism_profile":{"molecular_activity":[],"localization":[],"pathway":[],"complexes":["TgStx19-TgStx18 SNARE complex"],"partners":["TGSTX18"],"other_free_text":["TgStx19 is a Qc-SNARE that replaces the canonical Use1 partner of TgStx18 found in other eukaryotes [#0]","Conditional ablation of TgStx19 causes severe secretory system defects [#1]"]},"strain_conflicts":[]},"prefetch_data":{},"corpus_meta":[{"pmid":"34340555","id":"PMC_34340555","title":"The Dissection of SNAREs Reveals Key Factors for Vesicular Trafficking to the Endosome-like Compartment and Apicoplast via the Secretory System in Toxoplasma gondii.","date":"2021","source":"mBio","url":"https://pubmed.ncbi.nlm.nih.gov/34340555","citation_count":20,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":3189,"output_tokens":538,"usd":0.008818,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":5205,"output_tokens":1467,"usd":0.03135,"stage2_stop_reason":"end_turn"},"total_usd":0.040168,"stage1_batch_id":"msgbatch_01WokvBYTB6JLnYrpD4rXnyV","stage2_batch_id":"msgbatch_01M7hsQDvz6AqVC9DLVjQzzc","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2021,\n      \"finding\": \"TgStx19 is a novel Qc-SNARE localized to the endoplasmic reticulum (ER) in Toxoplasma gondii, where it acts as a binding partner of TgStx18, replacing the canonical Use1 partner found in other eukaryotes.\",\n      \"method\": \"Fluorescence localization experiments and conditional ablation (conditional knockout) with phenotypic analysis of secretory system defects\",\n      \"journal\": \"mBio\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct localization by imaging and conditional KO with defined secretory phenotype, single lab, two orthogonal methods\",\n      \"pmids\": [\"34340555\"],\n      \"is_preprint\": false,\n      \"attribution\": [\n        {\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}\n      ]\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Conditional ablation of TgStx19 (an ER-residing SNARE) caused severe defects in the secretory system, establishing its functional requirement for vesicular trafficking through the ER in Toxoplasma gondii.\",\n      \"method\": \"Conditional knockout with phenotypic analysis of secretory pathway defects\",\n      \"journal\": \"mBio\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — clean conditional KO with defined cellular phenotype, single lab, single method reported in abstract\",\n      \"pmids\": [\"34340555\"],\n      \"is_preprint\": false,\n      \"attribution\": [\n        {\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}\n      ]\n    }\n  ],\n  \"current_model\": \"TgStx19 is a novel Qc-SNARE that localizes to the endoplasmic reticulum in Toxoplasma gondii, where it functions as a partner of TgStx18 (replacing the canonical Use1) to mediate vesicular trafficking through the secretory system; its conditional ablation causes severe secretory defects.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"In Toxoplasma gondii, STX19 (TgStx19) is a novel Qc-SNARE that resides in the endoplasmic reticulum and functions in vesicular trafficking through the secretory system [#0]. It acts as a binding partner of TgStx18, substituting for the canonical Use1 partner found in other eukaryotes [#0]. Conditional ablation of TgStx19 causes severe defects in the secretory system, establishing its functional requirement for ER-based trafficking [#1]. Beyond these findings, no further mechanistic detail on TgStx19 has been characterized in the available corpus.\",\n  \"teleology\": [\n    {\n      \"year\": 2021,\n      \"claim\": \"It was unknown how the ER SNARE machinery is organized in Toxoplasma; imaging and conditional knockout established that TgStx19 is an ER-localized Qc-SNARE that partners with TgStx18 in place of the canonical Use1, defining a divergent SNARE architecture in this parasite.\",\n      \"evidence\": \"Fluorescence localization and conditional knockout with phenotypic analysis in Toxoplasma gondii\",\n      \"pmids\": [\"34340555\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Direct biochemical demonstration of the TgStx19-TgStx18 SNARE complex and its full R-SNARE/Qa/Qb composition is not established\",\n        \"The specific trafficking step and cargoes dependent on TgStx19 are not defined\"\n      ],\n      \"attribution\": [\n        {\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}\n      ]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Whether TgStx19 is functionally required was unknown; conditional ablation producing severe secretory-system defects established that TgStx19 is necessary for vesicular trafficking through the ER.\",\n      \"evidence\": \"Conditional knockout with phenotypic analysis of secretory pathway defects in Toxoplasma gondii\",\n      \"pmids\": [\"34340555\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"The molecular basis linking loss of TgStx19 to the secretory defect (fusion failure, mislocalization of partners) is not resolved\",\n        \"Impact on parasite viability, invasion, or virulence is not delineated in this corpus\"\n      ],\n      \"attribution\": [\n        {\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}\n      ]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The structural basis of TgStx19 SNARE-complex assembly, its complete set of interacting SNAREs, and the precise trafficking step it mediates remain undetermined.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"No structural or reconstituted-fusion characterization of the TgStx19 complex\",\n        \"No mapping of the exact ER trafficking substep or cargo dependence\"\n      ],\n      \"attribution\": [\n        {\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}\n      ]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0005484\", \"supporting_discovery_ids\": [0], \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005783\", \"supporting_discovery_ids\": [0, 1], \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"GO:0016192\", \"supporting_discovery_ids\": [0, 1], \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]}\n    ],\n    \"complexes\": [\"TgStx19-TgStx18 SNARE complex\"],\n    \"partners\": [\"TgStx18\"],\n    \"other_free_text\": [\n      \"TgStx19 is a Qc-SNARE that replaces the canonical Use1 partner of TgStx18 found in other eukaryotes [#0]\",\n      \"Conditional ablation of TgStx19 causes severe secretory system defects [#1]\"\n    ]\n  },\n  \"strain_conflicts\": []\n}","audit_flag":null,"strains":[{"strain":"ME49","gene_id":"TGME49_208010","name":"STX19","product":"syntaxin-19","uniprot_acc":"S8FF39","chromosome":"TGME49_chrIb","start_pos":509671},{"strain":"GT1","gene_id":"TGGT1_208010","name":null,"product":"hypothetical protein","uniprot_acc":null,"chromosome":"TGGT1_chrIb","start_pos":526454},{"strain":"RH88","gene_id":"TGRH88_022650","name":null,"product":"unspecified product","uniprot_acc":null,"chromosome":"CM023082","start_pos":1497388},{"strain":"VEG","gene_id":"TGVEG_208010","name":null,"product":"putative transmembrane protein","uniprot_acc":"A0A125YYS8","chromosome":"TGVEG_chrIb","start_pos":508972}]}