{"uniprot":"Q08AG7","gene":"MZT1","name":"Mitotic-spindle organizing protein 1","organism":"Homo sapiens (Human)","status":"dark","length":82,"sequence":"MASSSGAGAAAAAAAANLNAVRETMDVLLEISRILNTGLDMETLSICVRLCEQGINPEALSSVIKELRKATEALKAAENMTS","function_summary":"A cytoplasmic adaptor that organizes the mitotic spindle by assembling and positioning nucleation machinery. It concentrates and stabilizes microtubule-nucleating complexes at centrosomes and spindle poles, thereby promoting robust spindle assembly and integrity. Operating as a multivalent scaffold, it cycles between the cytosol and mitotic structures, capturing and delivering spindle-organizing assemblies to their sites of action to ensure faithful chromosome segregation.","plain_language":"MZT1 has barely been studied. The model's best guess: A cytoplasmic adaptor that organizes the mitotic spindle by assembling and positioning nucleation machinery. It concentrates and stabilizes microtubule-nucleating complexes at centrosomes and spindle poles, thereby promoting robust spindle assembly and integrity.","uniprot_summary":"Involved in mitotic spindle assembly.","go_terms":{"molecular_function":[{"id":"GO:0005515","label":"protein binding"}],"biological_process":[{"id":"GO:0031503","label":"protein-containing complex localization"}],"cellular_component":[{"id":"GO:0005829","label":"cytosol"},{"id":"GO:0000931","label":"gamma-tubulin ring complex"},{"id":"GO:0005813","label":"centrosome"},{"id":"GO:0005819","label":"spindle"}]},"interpro":[{"id":"IPR022214","name":"Mitotic-spindle organizing protein 1","type":"family","start":13,"end":79}],"reasoning":"I begin with the InterPro architecture: a single annotated module, IPR022214 (Mitotic-spindle organizing protein 1 family) spanning residues 13–79. This compact, centrally placed family signature defines a mitotic-spindle assembly factor rather than an enzyme. The absence of catalytic domains and the presence of a dedicated mitotic-spindle organizing family signature causally point to a scaffolding/adaptor role that operates through selective macromolecular contacts. Such adaptors typically mediate multivalent protein-protein interactions that nucleate and stabilize higher-order assemblies, which directly supports GO:0005515 protein binding as the primary molecular function.\n\nA spindle-organizing adaptor of this class drives assembly and positioning of microtubule-nucleating machinery. By binding and stabilizing components of the gamma-tubulin ring complex (γ-TuRC), it causes microtubule nucleation at centrosomes and spindle poles. This adaptor-driven assembly and placement of nucleation modules is the essence of GO:0031503 protein-containing complex localization: the architecture promotes the spatial targeting of large complexes (e.g., γ-TuRC and spindle-associated assemblies) to the centrosome and spindle apparatus.\n\nThe cellular geography follows from this logic. γ-TuRC is the core microtubule nucleator at centrosomes and spindle poles; therefore, a spindle-organizing adaptor is expected at the GO:0000931 gamma-tubulin ring complex and the GO:0005813 centrosome. During mitosis, it tracks to the GO:0005819 spindle, and between assembly events it resides in the soluble phase of the cytoplasm, consistent with GO:0005829 cytosol. This distribution—cytosolic pools feeding centrosomal and spindle-localized assemblies—matches the temporal demands of mitotic spindle formation and maintenance.\n\nMechanistically, the IPR022214 family signature indicates a hub that stabilizes γ-TuRC and associated targeting factors. By concentrating γ-tubulin and its grip subunits at centrosomes and spindle poles, the adaptor increases nucleation efficiency and fidelity, thereby ensuring robust bipolar spindle formation. I hypothesize that it binds γ-TuRC constituents and centrosomal scaffolds to choreograph complex localization: in interphase it may preassemble γ-TuRC at centrosomes; upon mitotic entry it escorts or anchors γ-TuRC to spindle poles, buffering microtubule minus ends and promoting spindle integrity.\n\nFrom this model, likely interaction partners include γ-TuRC core and accessory subunits (TUBG1/TUBG2 and GCP/N摄 modules), centrosomal scaffolds (pericentrin and CDK5RAP2), and spindle organizers (NuMA and dynein–dynactin). These associations would collectively explain its cytosolic-to-centrosomal trafficking and its central role in mitotic spindle organization.","category":"dark","control_evaluation":null,"validation_plan":null,"structure":{"source":"AlphaFold DB","pdb":"/structures/AF-Q08AG7.pdb","alphafold":"https://alphafold.ebi.ac.uk/entry/Q08AG7"},"links":{"uniprot":"https://www.uniprot.org/uniprotkb/Q08AG7/entry","atlas":"/p/Q08AG7"},"provenance":{"model":"BioReason-Pro (ESM3 esm3-sm-open-v1)","source_list":"Pharos Tdark","note":"AI prediction, not experimentally verified"}}