{"uniprot":"Q5VYM1","gene":"C9orf131","name":"Uncharacterized protein C9orf131","organism":"Homo sapiens (Human)","status":"dark","length":1079,"sequence":"MEWLLEDLLGAKGDMGLLWGQLTHALACRHCGSSCFQSPGNLVTLFLFVVWQIQRWWQLGRLRQLHPWCSGNMVQGKELPLLHRVAFLDHLCKQKSEVEEEGEEEEEGEDEASLDPLKPCSPTKEAPTGEQATPAPPQPSCGSEGLLKAIGIPEQTVMQPVSPSRSFPIFQILTSFPVRHKIASGNRQQQRKSQLFWGLPSLHSESLEAIFLSSGGPSPLKWSVCSSVFFNKLAFLPRSNLLLPQYHSSAQFSTHGAHTMEDLEGMAPDPQLLPPPSSPSVSSLLLHLRPFPVDHKGVLSGAEAPTQSPGTSPLEVLPGYETHLETTGHKKMPQAFEPPMPPPCQSPASLSEPRKVSPEGGLAISKDFWGTVGYREKPQASESSMPVPCPPLDSLPELQRESSLEDPSRYKPQWECRENSGNLWAFESPVLDLNPELSGTSPECVPPASETPWKGMQSRENIWVPADPVSPPSLPSVPLLESLVMGPQGVLSESKALWETMGQKENLWASDSPDPVHSTPPTTLMEPHRINPGECLATSEATWKDTEHSRNSSASRSPSLALSPPPALAPELLRVRSMGVLSDSEARCGDIQKTKNSWASKHPACNLPQDLHGASPLGVLSDSQSIVGEMEQKENCVPVFPGRGSSPSSNSVSKSHVSEPIADQSNYKPDGEAVEQRKNHWATELPAPSSLSTPLPEPHIDLELVWRNVQQREVPQGPSPLAVDPLHPVPQPPTLAEAVKIERTHPGLPKGVTCPGVKAEAPLSQRWTVPELLTHPGIHAWQWSRELKLRLKKLRQSPASRAPGPSQSFCSSPILSSTIPDFWGLPSCPPQQIYPPNPCPHSSSCHPQEVQRTVPQPVQSSHCHHFQSSSQLQPQESGRAEQGSQRGEKMKGKMVSQVPSQGPCVHMEAGVDYLSPGPGEPSNSKVLVSGKRKDKASASSSAKKREHPRKPKAGDHRRGTARLGLSTVTGKNHPAQARSLVEAPVSTFPQRSQHRGQSSQHTALPQLLLPKASGPQDQPEAGRRASDILTPRHCKHCPWAHMEKYLSFPTLKASLTRGLQKVLAKCLDNHRPLPTKSSQ","function_summary":"A large human assembly scaffold that uses extensive protein–protein interaction surfaces to organize the biogenesis of the vacuolar proton pump and associated trafficking pathways. Its architecture favors multivalent binding rather than catalysis, enabling it to stabilize and coordinate assembly intermediates of the proton-transporting complex. In germ cell contexts, it likely couples organelle assembly with nuclear programs by shuttling between cytoplasm and nucleus, thereby aligning endolysosomal acidification and vesicle dynamics with spermatogenic differentiation.","plain_language":"C9orf131 has barely been studied. The model's best guess: A large human assembly scaffold that uses extensive protein–protein interaction surfaces to organize the biogenesis of the vacuolar proton pump and associated trafficking pathways. Its architecture favors multivalent binding rather than catalysis, enabling it to stabilize and coordinate assembly intermediates of the proton-transporting complex.","uniprot_summary":"May be involved in spermatogenesis.","go_terms":{"molecular_function":[{"id":"GO:0005515","label":"protein binding"}],"biological_process":[{"id":"GO:0070070","label":"proton-transporting V-type ATPase complex assembly"}],"cellular_component":[{"id":"GO:0005634","label":"nucleus"}]},"interpro":[{"id":"IPR026677","name":"Spermatogenesis-associated protein 31G1-like","type":"family","start":308,"end":1079}],"reasoning":"I begin with the InterPro architecture. The sequence contains a single, expansive family signature IPR026677 (Spermatogenesis-associated protein 31G1-like, residues 308–1079). This family marks large, testis-enriched scaffolds that typically lack catalytic motifs and instead mediate assembly and regulation through multivalent interfaces. The breadth of the family domain across the C-terminal two-thirds of the polypeptide implies that the core functional determinants reside in this region, while the N-terminal portion likely contributes flexible, low-complexity segments that enhance protein–protein interactions. Such an architecture causally supports a non-enzymatic role dominated by binding and assembly, aligning with GO:0005515 protein binding as the primary molecular function.\n\nFrom this scaffold-like foundation, I infer the biological role by connecting assembly capacity to pathway specificity. The explicit linkage to proton pump biogenesis is captured by GO:0070070 proton-transporting V-type ATPase complex assembly. A large assembly factor with extensive binding surfaces is well-suited to chaperone and coordinate the stoichiometric assembly of membrane-bound V-ATPase subunits. In germ cells and other specialized lineages, regulated V-ATPase assembly tunes endolysosomal and secretory pathway acidification, which in turn governs cargo sorting and signaling. The testis-associated family signature suggests that this assembly role is deployed in spermatogenic contexts, where endolysosomal dynamics and nuclear signaling intersect.\n\nCellular localization follows from this logic. The presence of a nucleus-associated GO cellular component (GO:0005634 nucleus) indicates that the scaffold also operates in the nuclear compartment. A parsimonious model is that the protein shuttles between cytoplasm and nucleus, where it coordinates transcriptional or chromatin-associated programs that accompany V-ATPase assembly and trafficking demands. Nuclear residency would allow coupling between organelle biogenesis and gene regulatory circuits that are characteristic of germ cell differentiation.\n\nMechanistically, I propose that the IPR026677-driven scaffold nucleates transient assemblies that bring together V-ATPase subunits and assembly cofactors, stabilizing intermediates and guiding their maturation. In spermatogenic cells, this assembly hub likely interfaces with nuclear regulators to synchronize organelle acidification with developmental cues. The absence of catalytic domains and the dominance of interaction-prone regions causally enforce a role as an assembly adaptor rather than an enzyme.\n\nThis model predicts interaction partners and pathways. The scaffold should bind V-ATPase subunits and their assembly factors, and transiently associate with nuclear regulators that tune expression of pump components and trafficking machinery. In germ cells, it may bridge endolysosomal modules with chromatin-associated complexes to coordinate assembly with differentiation.","category":"dark","control_evaluation":null,"validation_plan":null,"structure":{"source":"AlphaFold DB","pdb":"/structures/AF-Q5VYM1.pdb","alphafold":"https://alphafold.ebi.ac.uk/entry/Q5VYM1"},"links":{"uniprot":"https://www.uniprot.org/uniprotkb/Q5VYM1/entry","atlas":"/p/Q5VYM1"},"provenance":{"model":"BioReason-Pro (ESM3 esm3-sm-open-v1)","source_list":"Pharos Tdark","note":"AI prediction, not experimentally verified"}}