{"gene":"TG_247230","gene_symbol":"CEN1","run_date":"2026-09-08T12:58:25","timeline":{"discoveries":[{"year":2020,"finding":"TgCEN1 binds two Ca2+ ions with high/medium affinity and undergoes significant Ca2+-dependent conformational changes that expose hydrophobic patches, supporting a role as a Ca2+ sensor; it also displays a Ca2+-dependent ability to self-assemble, distinguishing it from TgCEN2.","method":"Biophysical and structural approaches (Ca2+ binding assays, CD spectroscopy, fluorescence spectroscopy, dynamic light scattering)","journal":"Biomolecules","confidence":"Medium","confidence_rationale":"Tier 1–2 / Moderate — multiple orthogonal biophysical methods in a single study, single lab","pmids":["32759683"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2021,"finding":"TgCEN1 self-assembly depends on Ca2+ concentration, temperature, and protein concentration, is mediated by electrostatic and hydrophobic interactions, is abolished by removal of the first 21 N-terminal residues, and is reduced by the presence of the P17-XPC target peptide; a N-to-C self-assembly mode is supported whereby the first 21 residues of one molecule interact with the C-lobe of another.","method":"Dynamic light scattering, isothermal titration calorimetry, NMR, circular dichroism, fluorescence spectroscopy; N-terminal deletion mutant analysis","journal":"The Biochemical journal","confidence":"Medium","confidence_rationale":"Tier 1–2 / Moderate — multiple orthogonal biophysical methods including mutagenesis (N-terminal deletion), single lab","pmids":["34114596"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2021,"finding":"TgCEN1 possesses two target-binding sites with distinct affinities and Ca2+ sensitivity: a high-affinity site in the C-lobe that may constitutively bind target peptide (P17-XPC), and a low-affinity site in the N-lobe that is active only upon Ca2+ stimulus.","method":"Isothermal titration calorimetry, NMR, circular dichroism, and fluorescence spectroscopy using intact TgCEN1 and isolated N- and C-terminal lobe domains titrated with P17-XPC peptide","journal":"The Biochemical journal","confidence":"Medium","confidence_rationale":"Tier 1–2 / Moderate — multiple orthogonal in vitro binding methods with domain-level dissection, single lab","pmids":["34114596"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2022,"finding":"TgCEN1 directly binds repeat motifs of the centrosomal protein TgSFI1; different TgSFI1 repeats constitute distinct binding sites for TgCEN1 with differing binding affinities, Ca2+ sensitivity, and lobe-specific interaction modes, indicating conformational plasticity of TgCEN1 underlies dynamic Ca2+-regulated association with TgSFI1 at the centrosome.","method":"Isothermal titration calorimetry, NMR, circular dichroism, and fluorescence spectroscopy using TgCEN1, isolated N- and C-terminal domains, and synthetic peptides from TgSFI1 repeats","journal":"Biomolecules","confidence":"Medium","confidence_rationale":"Tier 1–2 / Moderate — multiple orthogonal biophysical binding assays with domain-level resolution, single lab","pmids":["36009009"],"is_preprint":false,"attribution":[{"species":"Toxoplasma gondii","strain":""}]}],"current_model":"TgCEN1 is a Ca2+-sensor centrin that binds two Ca2+ ions with high/medium affinity, undergoes Ca2+-dependent conformational changes exposing hydrophobic patches, self-assembles via N-terminal–C-lobe interactions in a Ca2+-, temperature-, and concentration-dependent manner, and directly engages the centrosomal protein TgSFI1 through lobe-specific, Ca2+-regulated binding modes at distinct repeat motifs, collectively supporting a role in dynamic centrosome architecture and Ca2+-modulated target recognition in Toxoplasma gondii."},"narrative":{"mechanistic_narrative":"TgCEN1 is a Ca2+-sensor centrin implicated in dynamic centrosome architecture and Ca2+-modulated target recognition in Toxoplasma gondii [PMID:32759683, PMID:36009009]. It binds two Ca2+ ions with high and medium affinity and undergoes Ca2+-dependent conformational changes that expose hydrophobic patches characteristic of a Ca2+ sensor [PMID:32759683]. TgCEN1 self-assembles in a Ca2+-, temperature-, and concentration-dependent manner through electrostatic and hydrophobic interactions, following an N-to-C mode in which the first 21 N-terminal residues of one molecule engage the C-lobe of another; deletion of these residues abolishes assembly, and the P17-XPC target peptide reduces it [PMID:32759683, PMID:34114596]. Target recognition is lobe-specific: a high-affinity C-lobe site can constitutively engage target peptide while a low-affinity N-lobe site becomes active only upon Ca2+ stimulus [PMID:34114596]. TgCEN1 directly binds distinct repeat motifs of the centrosomal protein TgSFI1 with differing affinities, Ca2+ sensitivities, and lobe-specific binding modes, so that its conformational plasticity underlies dynamic, Ca2+-regulated association with TgSFI1 at the centrosome [PMID:36009009]. Cellular and in vivo functional roles beyond these in vitro biophysical characterizations have not been established in the available corpus.","teleology":[{"year":2020,"claim":"Whether TgCEN1 functions as a Ca2+ sensor was unresolved; demonstrating two-site Ca2+ binding with conformational exposure of hydrophobic patches established its sensor behavior and distinguished it functionally from TgCEN2.","evidence":"Ca2+ binding assays, CD, fluorescence spectroscopy, and dynamic light scattering on recombinant TgCEN1","pmids":["32759683"],"confidence":"Medium","gaps":["No cellular localization or in vivo functional consequence tested","Physiological targets not yet identified"],"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2021,"claim":"How TgCEN1 self-associates was unknown; mapping self-assembly to an N-to-C interaction dependent on the first 21 residues defined the structural determinants of oligomerization and its modulation by Ca2+, temperature, and target peptide.","evidence":"DLS, ITC, NMR, CD, fluorescence spectroscopy, and N-terminal deletion mutant analysis","pmids":["34114596"],"confidence":"Medium","gaps":["Functional role of self-assembly in vivo untested","Higher-order assembly state and stoichiometry at the centrosome unknown"],"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2021,"claim":"The mode of target-peptide recognition was undefined; dissecting binding into a constitutive high-affinity C-lobe site and a Ca2+-activated low-affinity N-lobe site established a two-site, differentially Ca2+-regulated recognition mechanism.","evidence":"ITC, NMR, CD, and fluorescence spectroscopy on intact TgCEN1 and isolated lobes titrated with P17-XPC peptide","pmids":["34114596"],"confidence":"Medium","gaps":["P17-XPC is a model peptide, not a validated physiological target","Cellular relevance of lobe-specific binding not demonstrated"],"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":2022,"claim":"A physiological binding partner was lacking; showing direct, lobe-specific, Ca2+-sensitive binding to distinct repeat motifs of TgSFI1 connected TgCEN1's biophysical properties to a defined centrosomal target.","evidence":"ITC, NMR, CD, and fluorescence spectroscopy using TgCEN1, isolated lobes, and synthetic TgSFI1 repeat peptides","pmids":["36009009"],"confidence":"Medium","gaps":["Interaction shown with peptides in vitro, not full-length TgSFI1 in cells","Functional consequence for centrosome dynamics or parasite division untested"],"attribution":[{"species":"Toxoplasma gondii","strain":""}]},{"year":null,"claim":"The in vivo cellular function of TgCEN1 — its centrosomal localization, contribution to centrosome duplication or parasite division, and phenotype upon depletion — remains uncharacterized in the available corpus.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No genetic knockout or knockdown phenotype","No in-cell localization or division-cycle analysis","Interaction with full-length TgSFI1 in the parasite not confirmed"],"attribution":[{"species":"Toxoplasma gondii","strain":""}]}],"mechanism_profile":{"molecular_activity":[],"localization":[],"pathway":[],"complexes":[],"partners":["TGSFI1"],"other_free_text":["Binds two Ca2+ ions with high/medium affinity and exposes hydrophobic patches upon Ca2+ binding [#0]","Self-assembles via N-to-C mode requiring the first 21 N-terminal residues, engaging the C-lobe of a partner molecule [#1]","Two target-binding sites: constitutive high-affinity C-lobe site and Ca2+-activated low-affinity N-lobe site (probed with P17-XPC peptide) [#2]","Binds distinct TgSFI1 repeat motifs with differing affinities, Ca2+ sensitivities, and lobe-specific modes [#3]"]},"strain_conflicts":[]},"prefetch_data":{},"corpus_meta":[{"pmid":"34114596","id":"PMC_34114596","title":"The interplay of self-assembly and target binding in centrin 1 from Toxoplasma gondii.","date":"2021","source":"The Biochemical journal","url":"https://pubmed.ncbi.nlm.nih.gov/34114596","citation_count":13,"is_preprint":false},{"pmid":"32759683","id":"PMC_32759683","title":"Distinct Calcium Binding and Structural Properties of Two Centrin Isoforms from Toxoplasma gondii.","date":"2020","source":"Biomolecules","url":"https://pubmed.ncbi.nlm.nih.gov/32759683","citation_count":11,"is_preprint":false},{"pmid":"36009009","id":"PMC_36009009","title":"Conformational Plasticity of Centrin 1 from Toxoplasma gondii in Binding to the Centrosomal Protein SFI1.","date":"2022","source":"Biomolecules","url":"https://pubmed.ncbi.nlm.nih.gov/36009009","citation_count":8,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":3926,"output_tokens":1221,"usd":0.015047,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":6263,"output_tokens":2446,"usd":0.046233,"stage2_stop_reason":"end_turn"},"total_usd":0.06128,"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\": 2020,\n      \"finding\": \"TgCEN1 binds two Ca2+ ions with high/medium affinity and undergoes significant Ca2+-dependent conformational changes that expose hydrophobic patches, supporting a role as a Ca2+ sensor; it also displays a Ca2+-dependent ability to self-assemble, distinguishing it from TgCEN2.\",\n      \"method\": \"Biophysical and structural approaches (Ca2+ binding assays, CD spectroscopy, fluorescence spectroscopy, dynamic light scattering)\",\n      \"journal\": \"Biomolecules\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — multiple orthogonal biophysical methods in a single study, single lab\",\n      \"pmids\": [\"32759683\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"TgCEN1 self-assembly depends on Ca2+ concentration, temperature, and protein concentration, is mediated by electrostatic and hydrophobic interactions, is abolished by removal of the first 21 N-terminal residues, and is reduced by the presence of the P17-XPC target peptide; a N-to-C self-assembly mode is supported whereby the first 21 residues of one molecule interact with the C-lobe of another.\",\n      \"method\": \"Dynamic light scattering, isothermal titration calorimetry, NMR, circular dichroism, fluorescence spectroscopy; N-terminal deletion mutant analysis\",\n      \"journal\": \"The Biochemical journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — multiple orthogonal biophysical methods including mutagenesis (N-terminal deletion), single lab\",\n      \"pmids\": [\"34114596\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"TgCEN1 possesses two target-binding sites with distinct affinities and Ca2+ sensitivity: a high-affinity site in the C-lobe that may constitutively bind target peptide (P17-XPC), and a low-affinity site in the N-lobe that is active only upon Ca2+ stimulus.\",\n      \"method\": \"Isothermal titration calorimetry, NMR, circular dichroism, and fluorescence spectroscopy using intact TgCEN1 and isolated N- and C-terminal lobe domains titrated with P17-XPC peptide\",\n      \"journal\": \"The Biochemical journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — multiple orthogonal in vitro binding methods with domain-level dissection, single lab\",\n      \"pmids\": [\"34114596\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"TgCEN1 directly binds repeat motifs of the centrosomal protein TgSFI1; different TgSFI1 repeats constitute distinct binding sites for TgCEN1 with differing binding affinities, Ca2+ sensitivity, and lobe-specific interaction modes, indicating conformational plasticity of TgCEN1 underlies dynamic Ca2+-regulated association with TgSFI1 at the centrosome.\",\n      \"method\": \"Isothermal titration calorimetry, NMR, circular dichroism, and fluorescence spectroscopy using TgCEN1, isolated N- and C-terminal domains, and synthetic peptides from TgSFI1 repeats\",\n      \"journal\": \"Biomolecules\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — multiple orthogonal biophysical binding assays with domain-level resolution, single lab\",\n      \"pmids\": [\"36009009\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    }\n  ],\n  \"current_model\": \"TgCEN1 is a Ca2+-sensor centrin that binds two Ca2+ ions with high/medium affinity, undergoes Ca2+-dependent conformational changes exposing hydrophobic patches, self-assembles via N-terminal–C-lobe interactions in a Ca2+-, temperature-, and concentration-dependent manner, and directly engages the centrosomal protein TgSFI1 through lobe-specific, Ca2+-regulated binding modes at distinct repeat motifs, collectively supporting a role in dynamic centrosome architecture and Ca2+-modulated target recognition in Toxoplasma gondii.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"TgCEN1 is a Ca2+-sensor centrin implicated in dynamic centrosome architecture and Ca2+-modulated target recognition in Toxoplasma gondii [#0, #3]. It binds two Ca2+ ions with high and medium affinity and undergoes Ca2+-dependent conformational changes that expose hydrophobic patches characteristic of a Ca2+ sensor [#0]. TgCEN1 self-assembles in a Ca2+-, temperature-, and concentration-dependent manner through electrostatic and hydrophobic interactions, following an N-to-C mode in which the first 21 N-terminal residues of one molecule engage the C-lobe of another; deletion of these residues abolishes assembly, and the P17-XPC target peptide reduces it [#0, #1]. Target recognition is lobe-specific: a high-affinity C-lobe site can constitutively engage target peptide while a low-affinity N-lobe site becomes active only upon Ca2+ stimulus [#2]. TgCEN1 directly binds distinct repeat motifs of the centrosomal protein TgSFI1 with differing affinities, Ca2+ sensitivities, and lobe-specific binding modes, so that its conformational plasticity underlies dynamic, Ca2+-regulated association with TgSFI1 at the centrosome [#3]. Cellular and in vivo functional roles beyond these in vitro biophysical characterizations have not been established in the available corpus.\",\n  \"teleology\": [\n    {\n      \"year\": 2020,\n      \"claim\": \"Whether TgCEN1 functions as a Ca2+ sensor was unresolved; demonstrating two-site Ca2+ binding with conformational exposure of hydrophobic patches established its sensor behavior and distinguished it functionally from TgCEN2.\",\n      \"evidence\": \"Ca2+ binding assays, CD, fluorescence spectroscopy, and dynamic light scattering on recombinant TgCEN1\",\n      \"pmids\": [\"32759683\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No cellular localization or in vivo functional consequence tested\", \"Physiological targets not yet identified\"],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"How TgCEN1 self-associates was unknown; mapping self-assembly to an N-to-C interaction dependent on the first 21 residues defined the structural determinants of oligomerization and its modulation by Ca2+, temperature, and target peptide.\",\n      \"evidence\": \"DLS, ITC, NMR, CD, fluorescence spectroscopy, and N-terminal deletion mutant analysis\",\n      \"pmids\": [\"34114596\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Functional role of self-assembly in vivo untested\", \"Higher-order assembly state and stoichiometry at the centrosome unknown\"],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"The mode of target-peptide recognition was undefined; dissecting binding into a constitutive high-affinity C-lobe site and a Ca2+-activated low-affinity N-lobe site established a two-site, differentially Ca2+-regulated recognition mechanism.\",\n      \"evidence\": \"ITC, NMR, CD, and fluorescence spectroscopy on intact TgCEN1 and isolated lobes titrated with P17-XPC peptide\",\n      \"pmids\": [\"34114596\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"P17-XPC is a model peptide, not a validated physiological target\", \"Cellular relevance of lobe-specific binding not demonstrated\"],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"A physiological binding partner was lacking; showing direct, lobe-specific, Ca2+-sensitive binding to distinct repeat motifs of TgSFI1 connected TgCEN1's biophysical properties to a defined centrosomal target.\",\n      \"evidence\": \"ITC, NMR, CD, and fluorescence spectroscopy using TgCEN1, isolated lobes, and synthetic TgSFI1 repeat peptides\",\n      \"pmids\": [\"36009009\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Interaction shown with peptides in vitro, not full-length TgSFI1 in cells\", \"Functional consequence for centrosome dynamics or parasite division untested\"],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The in vivo cellular function of TgCEN1 — its centrosomal localization, contribution to centrosome duplication or parasite division, and phenotype upon depletion — remains uncharacterized in the available corpus.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No genetic knockout or knockdown phenotype\", \"No in-cell localization or division-cycle analysis\", \"Interaction with full-length TgSFI1 in the parasite not confirmed\"],\n      \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0005509\", \"supporting_discovery_ids\": [0], \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]},\n      {\"term_id\": \"GO:0048306\", \"supporting_discovery_ids\": [2, 3], \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]},\n      {\"term_id\": \"GO:0042803\", \"supporting_discovery_ids\": [0, 1], \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005813\", \"supporting_discovery_ids\": [3], \"attribution\": [{\"species\": \"Toxoplasma gondii\", \"strain\": \"\"}]}\n    ],\n    \"pathway\": [],\n    \"complexes\": [],\n    \"partners\": [\"TgSFI1\"],\n    \"other_free_text\": [\n      \"Binds two Ca2+ ions with high/medium affinity and exposes hydrophobic patches upon Ca2+ binding [#0]\",\n      \"Self-assembles via N-to-C mode requiring the first 21 N-terminal residues, engaging the C-lobe of a partner molecule [#1]\",\n      \"Two target-binding sites: constitutive high-affinity C-lobe site and Ca2+-activated low-affinity N-lobe site (probed with P17-XPC peptide) [#2]\",\n      \"Binds distinct TgSFI1 repeat motifs with differing affinities, Ca2+ sensitivities, and lobe-specific modes [#3]\"\n    ]\n  },\n  \"strain_conflicts\": []\n}\n```","audit_flag":null,"strains":[{"strain":"ME49","gene_id":"TGME49_247230","name":"CEN1","product":"centrin 1","uniprot_acc":"A0A125YHX7","chromosome":"TGME49_chrXII","start_pos":3180840},{"strain":"GT1","gene_id":"TGGT1_247230","name":null,"product":"centrin","uniprot_acc":null,"chromosome":"TGGT1_chrXII","start_pos":3112753},{"strain":"RH88","gene_id":"TGRH88_061320","name":null,"product":"centrin","uniprot_acc":null,"chromosome":"CM023093","start_pos":3234147},{"strain":"VEG","gene_id":"TGVEG_247230","name":null,"product":"centrin","uniprot_acc":"B9QDJ3","chromosome":"TGVEG_chrXII","start_pos":3149918}]}