{"gene":"TG_245428","gene_symbol":"GRA19","run_date":"2026-09-08T12:58:25","timeline":{"discoveries":[{"year":2013,"finding":"GRA19 contains a HT/PEXEL-like motif (RxLxD/E) at its N-terminus and localizes to the parasitophorous vacuole membrane (PVM); site-directed mutagenesis showed that arginine and leucine residues within this motif are required for protein cleavage, and cleavage promotes increased PVM association. Unlike Plasmodium PEXEL proteins, GRA19 is not exported into the host cell.","method":"Hemagglutinin/Myc epitope tagging, co-localization with PVM markers, site-directed mutagenesis of the HT/PEXEL motif, subcellular fractionation","journal":"Traffic (Copenhagen, Denmark)","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct mutagenesis and localization experiments in a single lab with two orthogonal methods (tagging + mutagenesis)","pmids":["23356236"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2015,"finding":"The Golgi-resident aspartyl protease ASP5 cleaves GRA19 at its PEXEL-like motif; in ASP5 knockout parasites, GRA19 cleavage is abolished, demonstrating that ASP5 is the specific processing enzyme for GRA19.","method":"ASP5 gene deletion (knockout), protein cleavage assay by western blot/immunofluorescence comparing wild-type and Δasp5 parasites","journal":"PLoS pathogens","confidence":"High","confidence_rationale":"Tier 2 / Strong — clean genetic knockout with direct biochemical demonstration of loss of cleavage, replicated across multiple GRA substrates in one rigorous study","pmids":["26473595"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]}],"current_model":"GRA19 is a dense granule protein that localizes to the parasitophorous vacuole membrane (PVM) via its N-terminal HT/PEXEL-like motif (RxLxD/E); this motif is cleaved by the Golgi-resident aspartyl protease ASP5, and cleavage promotes stable PVM association, but unlike Plasmodium PEXEL proteins, GRA19 is not exported across the PVM into the host cell."},"narrative":{"mechanistic_narrative":"GRA19 is a Toxoplasma gondii dense granule protein that associates with the parasitophorous vacuole membrane (PVM) through an N-terminal HT/PEXEL-like motif (RxLxD/E), whose conserved arginine and leucine residues are required for proteolytic cleavage; this cleavage promotes stable PVM association, yet unlike Plasmodium PEXEL proteins GRA19 is not exported across the PVM into the host cell [PMID:23356236]. Processing at this motif is carried out by the Golgi-resident aspartyl protease ASP5, since GRA19 cleavage is abolished in Δasp5 parasites [PMID:26473595]. Beyond its ASP5-dependent maturation and PVM targeting, no further mechanistic detail — including molecular function at the PVM or interacting partners — has been characterized in the available corpus.","teleology":[{"year":2013,"claim":"Whether GRA19's PEXEL-like motif drives host-cell export as in Plasmodium or serves a distinct role was unknown; mapping the motif established that its cleavage governs PVM association without host export, defining a Toxoplasma-specific use of the PEXEL element.","evidence":"Epitope tagging, PVM marker co-localization, site-directed mutagenesis of the RxLxD/E motif, and subcellular fractionation in T. gondii","pmids":["23356236"],"confidence":"Medium","gaps":["The protease responsible for motif cleavage was not identified in this study","The functional consequence of PVM association for the parasite or vacuole is unknown","No interacting partners or downstream activity at the PVM defined"],"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2015,"claim":"The identity of the enzyme processing GRA19's PEXEL-like motif was open; genetic deletion of ASP5 abolished cleavage, establishing ASP5 as the specific maturase for GRA19.","evidence":"ASP5 gene knockout with cleavage assessed by western blot/immunofluorescence comparing wild-type and Δasp5 T. gondii","pmids":["26473595"],"confidence":"High","gaps":["Whether ASP5-dependent cleavage is required for any GRA19 biological function is not resolved","The molecular activity of mature GRA19 at the PVM remains undefined"],"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":null,"claim":"The molecular function of GRA19 at the PVM and its interaction partners remain uncharacterized.","evidence":"No discovery in the available corpus addresses GRA19 function beyond motif cleavage and PVM localization","pmids":[],"confidence":"Low","gaps":["No molecular activity assigned to GRA19","No binding partners or complex membership identified","No parasite phenotype associated with GRA19 loss reported"],"attribution":[{"species":"Toxoplasma gondii","strain":""}]}],"mechanism_profile":{"molecular_activity":[],"localization":[],"pathway":[],"complexes":[],"partners":["ASP5 (GOLGI-RESIDENT ASPARTYL PROTEASE THAT CLEAVES GRA19)"],"other_free_text":["GRA19 is a dense granule protein bearing an N-terminal HT/PEXEL-like motif (RxLxD/E) whose arginine and leucine residues are required for cleavage.","ASP5-dependent cleavage of the PEXEL-like motif promotes stable PVM association.","Unlike Plasmodium PEXEL proteins, GRA19 is not exported across the PVM into the host cell."]},"strain_conflicts":[]},"prefetch_data":{},"corpus_meta":[{"pmid":"26473595","id":"PMC_26473595","title":"Fundamental Roles of the Golgi-Associated Toxoplasma Aspartyl Protease, ASP5, at the Host-Parasite Interface.","date":"2015","source":"PLoS pathogens","url":"https://pubmed.ncbi.nlm.nih.gov/26473595","citation_count":95,"is_preprint":false},{"pmid":"23356236","id":"PMC_23356236","title":"A HT/PEXEL motif in Toxoplasma dense granule proteins is a signal for protein cleavage but not export into the host cell.","date":"2013","source":"Traffic (Copenhagen, Denmark)","url":"https://pubmed.ncbi.nlm.nih.gov/23356236","citation_count":53,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":3443,"output_tokens":691,"usd":0.010347,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":5410,"output_tokens":1473,"usd":0.031938,"stage2_stop_reason":"end_turn"},"total_usd":0.042285,"stage1_batch_id":"msgbatch_01TEPNZ4MCzJ7xtsNwosiDRk","stage2_batch_id":"msgbatch_01FQShM7n1sfCr4pWTDShmki","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2013,\n      \"finding\": \"GRA19 contains a HT/PEXEL-like motif (RxLxD/E) at its N-terminus and localizes to the parasitophorous vacuole membrane (PVM); site-directed mutagenesis showed that arginine and leucine residues within this motif are required for protein cleavage, and cleavage promotes increased PVM association. Unlike Plasmodium PEXEL proteins, GRA19 is not exported into the host cell.\",\n      \"method\": \"Hemagglutinin/Myc epitope tagging, co-localization with PVM markers, site-directed mutagenesis of the HT/PEXEL motif, subcellular fractionation\",\n      \"journal\": \"Traffic (Copenhagen, Denmark)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct mutagenesis and localization experiments in a single lab with two orthogonal methods (tagging + mutagenesis)\",\n      \"pmids\": [\"23356236\"],\n      \"is_preprint\": false,\n      \"attribution\": [\n        {\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}\n      ]\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"The Golgi-resident aspartyl protease ASP5 cleaves GRA19 at its PEXEL-like motif; in ASP5 knockout parasites, GRA19 cleavage is abolished, demonstrating that ASP5 is the specific processing enzyme for GRA19.\",\n      \"method\": \"ASP5 gene deletion (knockout), protein cleavage assay by western blot/immunofluorescence comparing wild-type and Δasp5 parasites\",\n      \"journal\": \"PLoS pathogens\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — clean genetic knockout with direct biochemical demonstration of loss of cleavage, replicated across multiple GRA substrates in one rigorous study\",\n      \"pmids\": [\"26473595\"],\n      \"is_preprint\": false,\n      \"attribution\": [\n        {\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}\n      ]\n    }\n  ],\n  \"current_model\": \"GRA19 is a dense granule protein that localizes to the parasitophorous vacuole membrane (PVM) via its N-terminal HT/PEXEL-like motif (RxLxD/E); this motif is cleaved by the Golgi-resident aspartyl protease ASP5, and cleavage promotes stable PVM association, but unlike Plasmodium PEXEL proteins, GRA19 is not exported across the PVM into the host cell.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"GRA19 is a Toxoplasma gondii dense granule protein that associates with the parasitophorous vacuole membrane (PVM) through an N-terminal HT/PEXEL-like motif (RxLxD/E), whose conserved arginine and leucine residues are required for proteolytic cleavage; this cleavage promotes stable PVM association, yet unlike Plasmodium PEXEL proteins GRA19 is not exported across the PVM into the host cell [#0]. Processing at this motif is carried out by the Golgi-resident aspartyl protease ASP5, since GRA19 cleavage is abolished in Δasp5 parasites [#1]. Beyond its ASP5-dependent maturation and PVM targeting, no further mechanistic detail — including molecular function at the PVM or interacting partners — has been characterized in the available corpus.\",\n  \"teleology\": [\n    {\n      \"year\": 2013,\n      \"claim\": \"Whether GRA19's PEXEL-like motif drives host-cell export as in Plasmodium or serves a distinct role was unknown; mapping the motif established that its cleavage governs PVM association without host export, defining a Toxoplasma-specific use of the PEXEL element.\",\n      \"evidence\": \"Epitope tagging, PVM marker co-localization, site-directed mutagenesis of the RxLxD/E motif, and subcellular fractionation in T. gondii\",\n      \"pmids\": [\"23356236\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"The protease responsible for motif cleavage was not identified in this study\",\n        \"The functional consequence of PVM association for the parasite or vacuole is unknown\",\n        \"No interacting partners or downstream activity at the PVM defined\"\n      ],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"The identity of the enzyme processing GRA19's PEXEL-like motif was open; genetic deletion of ASP5 abolished cleavage, establishing ASP5 as the specific maturase for GRA19.\",\n      \"evidence\": \"ASP5 gene knockout with cleavage assessed by western blot/immunofluorescence comparing wild-type and Δasp5 T. gondii\",\n      \"pmids\": [\"26473595\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Whether ASP5-dependent cleavage is required for any GRA19 biological function is not resolved\",\n        \"The molecular activity of mature GRA19 at the PVM remains undefined\"\n      ],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The molecular function of GRA19 at the PVM and its interaction partners remain uncharacterized.\",\n      \"evidence\": \"No discovery in the available corpus addresses GRA19 function beyond motif cleavage and PVM localization\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\n        \"No molecular activity assigned to GRA19\",\n        \"No binding partners or complex membership identified\",\n        \"No parasite phenotype associated with GRA19 loss reported\"\n      ],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [],\n    \"localization\": [\n      {\"term_id\": \"GO:0020005\", \"supporting_discovery_ids\": [0], \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]}\n    ],\n    \"pathway\": [],\n    \"complexes\": [],\n    \"partners\": [\"ASP5 (Golgi-resident aspartyl protease that cleaves GRA19)\"],\n    \"other_free_text\": [\n      \"GRA19 is a dense granule protein bearing an N-terminal HT/PEXEL-like motif (RxLxD/E) whose arginine and leucine residues are required for cleavage.\",\n      \"ASP5-dependent cleavage of the PEXEL-like motif promotes stable PVM association.\",\n      \"Unlike Plasmodium PEXEL proteins, GRA19 is not exported across the PVM into the host cell.\"\n    ]\n  },\n  \"strain_conflicts\": []\n}\n```","audit_flag":null,"strains":[{"strain":"ME49","gene_id":"TGME49_245428","name":null,"product":"hypothetical protein","uniprot_acc":"S8EUY6","chromosome":"TGME49_chrXII","start_pos":2251553},{"strain":"ME49","gene_id":"TGME49_245432","name":"GRA19","product":"dense granule protein GRA19","uniprot_acc":"S8G946","chromosome":"TGME49_chrXII","start_pos":2254309},{"strain":"GT1","gene_id":"TGGT1_245428","name":null,"product":"hypothetical protein","uniprot_acc":null,"chromosome":"AAQM03000491","start_pos":372},{"strain":"GT1","gene_id":"TGGT1_245432","name":null,"product":"hypothetical protein","uniprot_acc":null,"chromosome":"TGGT1_chrXII","start_pos":2190528},{"strain":"RH88","gene_id":"TGRH88_059990","name":null,"product":"unspecified product","uniprot_acc":null,"chromosome":"CM023093","start_pos":2266867},{"strain":"RH88","gene_id":"TGRH88_060020","name":null,"product":"unspecified product","uniprot_acc":null,"chromosome":"CM023093","start_pos":2282358},{"strain":"VEG","gene_id":"TGVEG_245432","name":null,"product":"hypothetical protein","uniprot_acc":"B6KGK0","chromosome":"TGVEG_chrXII","start_pos":2222916}]}