{"gene":"TG_280740","gene_symbol":"","run_date":"2026-09-08T14:08:30","timeline":{"discoveries":[{"year":2000,"finding":"TgMIC5 is expressed as a preproprotein and is proteolytically processed by signal peptidase to yield a proprotein intermediate, which is then further processed to a mature 22 kDa protein stored in micronemes before secretion.","method":"Molecular cloning, DNA sequence analysis, cell fractionation, protein secretion experiments, immunofluorescence and immunoelectron microscopy","journal":"Molecular and biochemical parasitology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal methods (biochemical fractionation, IFA, immuno-EM) in a single study establishing signal peptidase cleavage as the first processing step of TgMIC5","pmids":["11087916"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2011,"finding":"Signal peptidase cleavage defines the N-terminus of MIC propeptides (proM2AP and proMIC5), and the aliphatic residue immediately at or near the signal peptidase cleavage site (valine at +3 of proM2AP; leucine at +1 of proMIC5) is required for forward targeting to micronemes; conservative substitution between valine and leucine preserves targeting, confirming a shared aliphatic side-chain-dependent mechanism downstream of signal peptidase cleavage.","method":"N-terminal deletion and site-directed mutagenesis of propeptides combined with subcellular localization readout (trafficking assays); propeptide swapping between T. gondii MICs and EtMIC5","journal":"Traffic (Copenhagen, Denmark)","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal domain-swap and mutagenesis with multiple MIC substrates (M2AP, MIC5, AMA1, MIC3, EtMIC5) converging on the same conclusion, multiple orthogonal experiments within a single rigorous study","pmids":["21438967"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]}],"current_model":"In Toxoplasma gondii, signal peptidase cleaves preproproteins of microneme proteins (e.g., TgMIC5, M2AP) to generate propeptide intermediates whose extreme N-terminal aliphatic residues (valine or leucine at or near the cleavage site) are essential for forward trafficking of the proprotein to micronemes, after which additional proteolytic processing yields the mature secreted form."},"narrative":{"mechanistic_narrative":"In Toxoplasma gondii, signal peptidase carries out the first proteolytic step in the maturation of secretory microneme proteins, cleaving preproproteins such as TgMIC5 to generate a proprotein intermediate that is subsequently processed to the mature, micronemal form [PMID:11087916]. This cleavage defines the N-terminus of the resulting MIC propeptide, and the aliphatic residue positioned at or near the cleavage site (valine at +3 of proM2AP, leucine at +1 of proMIC5) is required for forward trafficking of the proprotein to the micronemes; conservative valine-to-leucine substitution preserves targeting, establishing a shared aliphatic side-chain-dependent trafficking mechanism downstream of signal peptidase cleavage [PMID:21438967]. Beyond its role in defining these propeptide N-termini and the downstream trafficking determinant, no further mechanistic detail on the signal peptidase enzyme itself has been characterized in the available corpus.","teleology":[{"year":2000,"claim":"Establishing that TgMIC5 is a preproprotein clarified that microneme proteins undergo an ordered maturation cascade, with signal peptidase cleavage as the defined first proteolytic step preceding storage and secretion.","evidence":"Molecular cloning, cell fractionation, secretion assays, immunofluorescence and immuno-EM in Toxoplasma gondii","pmids":["11087916"],"confidence":"Medium","gaps":["The identity and biochemistry of the signal peptidase enzyme itself were not characterized","The nature of the further processing step yielding the mature 22 kDa product was not defined"],"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2011,"claim":"Mutagenesis defined why signal peptidase cleavage matters for trafficking: the aliphatic residue it exposes at the propeptide N-terminus is the determinant required for forward targeting of MIC proproteins to micronemes.","evidence":"N-terminal deletion and site-directed mutagenesis of propeptides with subcellular localization readouts and propeptide swapping across T. gondii MICs and EtMIC5","pmids":["21438967"],"confidence":"High","gaps":["The trafficking machinery that reads the aliphatic N-terminal residue was not identified","The enzyme mediating the subsequent maturation of proprotein to mature MIC was not established","The generality beyond the tested MIC substrates was not fully explored"],"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":null,"claim":"The molecular identity, structure, and catalytic mechanism of the Toxoplasma signal peptidase, and how the exposed aliphatic N-terminus is recognized by the trafficking machinery, remain unresolved in the available corpus.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No structural or enzymatic characterization of the signal peptidase itself","No receptor or adaptor identified for the aliphatic N-terminal trafficking signal"],"attribution":[{"species":"Toxoplasma gondii","strain":""}]}],"mechanism_profile":{"molecular_activity":[],"localization":[],"pathway":[],"complexes":[],"partners":["TGMIC5 (SUBSTRATE)","M2AP (SUBSTRATE)"],"other_free_text":["Cleaves microneme preproproteins to generate proprotein intermediates whose exposed aliphatic N-terminal residue (Val or Leu) is required for forward trafficking to micronemes.","Substrate propeptides studied include proM2AP, proMIC5, AMA1, MIC3, and EtMIC5."]},"strain_conflicts":[]},"prefetch_data":{},"corpus_meta":[{"pmid":"11087916","id":"PMC_11087916","title":"Molecular characterization of TgMIC5, a proteolytically processed antigen secreted from the micronemes of Toxoplasma gondii.","date":"2000","source":"Molecular and biochemical parasitology","url":"https://pubmed.ncbi.nlm.nih.gov/11087916","citation_count":59,"is_preprint":false},{"pmid":"21438967","id":"PMC_21438967","title":"Forward targeting of Toxoplasma gondii proproteins to the micronemes involves conserved aliphatic amino acids.","date":"2011","source":"Traffic (Copenhagen, Denmark)","url":"https://pubmed.ncbi.nlm.nih.gov/21438967","citation_count":29,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":3443,"output_tokens":723,"usd":0.010587,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":5472,"output_tokens":1648,"usd":0.03428,"stage2_stop_reason":"end_turn"},"total_usd":0.044867,"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\": 2000,\n      \"finding\": \"TgMIC5 is expressed as a preproprotein and is proteolytically processed by signal peptidase to yield a proprotein intermediate, which is then further processed to a mature 22 kDa protein stored in micronemes before secretion.\",\n      \"method\": \"Molecular cloning, DNA sequence analysis, cell fractionation, protein secretion experiments, immunofluorescence and immunoelectron microscopy\",\n      \"journal\": \"Molecular and biochemical parasitology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal methods (biochemical fractionation, IFA, immuno-EM) in a single study establishing signal peptidase cleavage as the first processing step of TgMIC5\",\n      \"pmids\": [\"11087916\"],\n      \"is_preprint\": false,\n      \"attribution\": [\n        {\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}\n      ]\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Signal peptidase cleavage defines the N-terminus of MIC propeptides (proM2AP and proMIC5), and the aliphatic residue immediately at or near the signal peptidase cleavage site (valine at +3 of proM2AP; leucine at +1 of proMIC5) is required for forward targeting to micronemes; conservative substitution between valine and leucine preserves targeting, confirming a shared aliphatic side-chain-dependent mechanism downstream of signal peptidase cleavage.\",\n      \"method\": \"N-terminal deletion and site-directed mutagenesis of propeptides combined with subcellular localization readout (trafficking assays); propeptide swapping between T. gondii MICs and EtMIC5\",\n      \"journal\": \"Traffic (Copenhagen, Denmark)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal domain-swap and mutagenesis with multiple MIC substrates (M2AP, MIC5, AMA1, MIC3, EtMIC5) converging on the same conclusion, multiple orthogonal experiments within a single rigorous study\",\n      \"pmids\": [\"21438967\"],\n      \"is_preprint\": false,\n      \"attribution\": [\n        {\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}\n      ]\n    }\n  ],\n  \"current_model\": \"In Toxoplasma gondii, signal peptidase cleaves preproproteins of microneme proteins (e.g., TgMIC5, M2AP) to generate propeptide intermediates whose extreme N-terminal aliphatic residues (valine or leucine at or near the cleavage site) are essential for forward trafficking of the proprotein to micronemes, after which additional proteolytic processing yields the mature secreted form.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"In Toxoplasma gondii, signal peptidase carries out the first proteolytic step in the maturation of secretory microneme proteins, cleaving preproproteins such as TgMIC5 to generate a proprotein intermediate that is subsequently processed to the mature, micronemal form [#0]. This cleavage defines the N-terminus of the resulting MIC propeptide, and the aliphatic residue positioned at or near the cleavage site (valine at +3 of proM2AP, leucine at +1 of proMIC5) is required for forward trafficking of the proprotein to the micronemes; conservative valine-to-leucine substitution preserves targeting, establishing a shared aliphatic side-chain-dependent trafficking mechanism downstream of signal peptidase cleavage [#1]. Beyond its role in defining these propeptide N-termini and the downstream trafficking determinant, no further mechanistic detail on the signal peptidase enzyme itself has been characterized in the available corpus.\",\n  \"teleology\": [\n    {\n      \"year\": 2000,\n      \"claim\": \"Establishing that TgMIC5 is a preproprotein clarified that microneme proteins undergo an ordered maturation cascade, with signal peptidase cleavage as the defined first proteolytic step preceding storage and secretion.\",\n      \"evidence\": \"Molecular cloning, cell fractionation, secretion assays, immunofluorescence and immuno-EM in Toxoplasma gondii\",\n      \"pmids\": [\n        \"11087916\"\n      ],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"The identity and biochemistry of the signal peptidase enzyme itself were not characterized\",\n        \"The nature of the further processing step yielding the mature 22 kDa product was not defined\"\n      ],\n      \"attribution\": [\n        {\n          \"species\": \"Toxoplasma gondii\",\n          \"strain\": \"\"\n        }\n      ]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Mutagenesis defined why signal peptidase cleavage matters for trafficking: the aliphatic residue it exposes at the propeptide N-terminus is the determinant required for forward targeting of MIC proproteins to micronemes.\",\n      \"evidence\": \"N-terminal deletion and site-directed mutagenesis of propeptides with subcellular localization readouts and propeptide swapping across T. gondii MICs and EtMIC5\",\n      \"pmids\": [\n        \"21438967\"\n      ],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"The trafficking machinery that reads the aliphatic N-terminal residue was not identified\",\n        \"The enzyme mediating the subsequent maturation of proprotein to mature MIC was not established\",\n        \"The generality beyond the tested MIC substrates was not fully explored\"\n      ],\n      \"attribution\": [\n        {\n          \"species\": \"Toxoplasma gondii\",\n          \"strain\": \"\"\n        }\n      ]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The molecular identity, structure, and catalytic mechanism of the Toxoplasma signal peptidase, and how the exposed aliphatic N-terminus is recognized by the trafficking machinery, remain unresolved in the available corpus.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"No structural or enzymatic characterization of the signal peptidase itself\",\n        \"No receptor or adaptor identified for the aliphatic N-terminal trafficking signal\"\n      ],\n      \"attribution\": [\n        {\n          \"species\": \"Toxoplasma gondii\",\n          \"strain\": \"\"\n        }\n      ]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\n        \"term_id\": \"GO:0008233\",\n        \"supporting_discovery_ids\": [0, 1],\n        \"attribution\": [\n          {\n            \"species\": \"Toxoplasma gondii\",\n            \"strain\": \"\"\n          }\n        ]\n      }\n    ],\n    \"localization\": [],\n    \"pathway\": [\n      {\n        \"term_id\": \"GO:0006886\",\n        \"supporting_discovery_ids\": [1],\n        \"attribution\": [\n          {\n            \"species\": \"Toxoplasma gondii\",\n            \"strain\": \"\"\n          }\n        ]\n      }\n    ],\n    \"complexes\": [],\n    \"partners\": [\n      \"TgMIC5 (substrate)\",\n      \"M2AP (substrate)\"\n    ],\n    \"other_free_text\": [\n      \"Cleaves microneme preproproteins to generate proprotein intermediates whose exposed aliphatic N-terminal residue (Val or Leu) is required for forward trafficking to micronemes.\",\n      \"Substrate propeptides studied include proM2AP, proMIC5, AMA1, MIC3, and EtMIC5.\"\n    ]\n  },\n  \"strain_conflicts\": []\n}","audit_flag":null,"strains":[{"strain":"ME49","gene_id":"TGME49_280740","name":null,"product":"signal peptidase","uniprot_acc":"A0A125YQA1","chromosome":"TGME49_chrVIIa","start_pos":129953},{"strain":"GT1","gene_id":"TGGT1_280740","name":null,"product":"signal peptidase","uniprot_acc":null,"chromosome":"TGGT1_chrVIIa","start_pos":110222},{"strain":"RH88","gene_id":"TGRH88_032660","name":null,"product":"signal peptidase","uniprot_acc":null,"chromosome":"CM023088","start_pos":191370},{"strain":"VEG","gene_id":"TGVEG_280740","name":null,"product":"signal peptidase","uniprot_acc":"B9Q1Z7","chromosome":"TGVEG_chrVIIa","start_pos":171012}]}