{"uniprot":"Q8NH64","gene":"OR51A7","name":"Olfactory receptor 51A7","organism":"Homo sapiens (Human)","status":"dark","length":312,"sequence":"MSVLNNSEVKLFLLIGIPGLEHAHIWFSIPICLMYLLAIMGNCTILFIIKTEPSLHEPMYYFLAMLAVSDMGLSLSSLPTMLRVFLFNAMGISPNACFAQEFFIHGFTVMESSVLLIMSLDRFLAIHNPLRYSSILTSNRVAKMGLILAIRSILLVIPFPFTLRRLKYCQKNLLSHSYCLHQDTMKLACSDNKTNVIYGFFIALCTMLDLALIVLSYVLILKTILSIASLAERLKALNTCVSHICAVLTFYVPIITLAAMHHFAKHKSPLVVILIADMFLLVPPLMNPIVYCVKTRQIWEKILGKLLNVCGR","function_summary":"A human seven-transmembrane receptor at the cell surface that detects hydrophobic odorant-like ligands and transduces this extracellular cue into intracellular signaling via heterotrimeric G proteins. By assembling and activating G protein pathways at the plasma membrane, it modulates second-messenger and kinase networks that can influence proliferative programs in epithelial and immune contexts. Its multi-pass architecture anchors it in the membrane, where ligand-triggered conformational changes drive protein–protein interactions that govern signal amplitude and duration.","plain_language":"OR51A7 has barely been studied. The model's best guess: A human seven-transmembrane receptor at the cell surface that detects hydrophobic odorant-like ligands and transduces this extracellular cue into intracellular signaling via heterotrimeric G proteins. By assembling and activating G protein pathways at the plasma membrane, it modulates second-messenger and kinase networks that can influence proliferative programs in epithelial and immune contexts.","uniprot_summary":"Odorant receptor.","go_terms":{"molecular_function":[{"id":"GO:0005515","label":"protein binding"}],"biological_process":[{"id":"GO:0042127","label":"regulation of cell population proliferation"}],"cellular_component":[{"id":"GO:0005886","label":"plasma membrane"}]},"interpro":[{"id":"IPR017452","name":"GPCR, rhodopsin-like, 7TM","type":"domain","start":41,"end":291},{"id":"IPR050402","name":"Olfactory receptor 51/52/56-like","type":"family","start":6,"end":303},{"id":"IPR000276","name":"G protein-coupled receptor, rhodopsin-like","type":"family","start":26,"end":50},{"id":"IPR000725","name":"Olfactory receptor","type":"family","start":31,"end":306},{"id":"IPR000276","name":"G protein-coupled receptor, rhodopsin-like","type":"family","start":59,"end":80},{"id":"IPR000276","name":"G protein-coupled receptor, rhodopsin-like","type":"family","start":104,"end":126},{"id":"IPR000276","name":"G protein-coupled receptor, rhodopsin-like","type":"family","start":273,"end":299}],"reasoning":"I begin with the InterPro architecture. The core transmembrane engine is IPR017452 (GPCR, rhodopsin-like, 7TM domain, residues 41–291), which encodes the canonical seven-helix bundle that transduces extracellular ligand binding into intracellular G protein activation. This structural core is embedded within multiple olfactory/rhodopsin-like GPCR family signatures that span nearly the full length of the protein: IPR050402 (Olfactory receptor 51/52/56-like family, residues 6–303) and IPR000725 (Olfactory receptor family, residues 31–306) specify membership in the olfactory receptor clade of class A GPCRs, while three overlapping rhodopsin-like GPCR family entries—IPR000276 (residues 26–50), IPR000276 (residues 59–80), and IPR000276 (residues 104–126)—plus a late-stage motif IPR000276 (residues 273–299) collectively mark hallmark intracellular loop and helix features that couple to heterotrimeric G proteins. The ordered layout—an N-terminal extracellular region feeding into a 7TM bundle and concluding with intracellular loop 3 and C-terminal tail—creates a receptor that binds small hydrophobic ligands in a membrane context and signals through G proteins.\n\nThis architecture causes a molecular function centered on receptor-mediated protein binding. The 7TM fold and conserved cytosolic motifs drive high-affinity coupling to heterotrimeric G proteins and associated effectors, which is captured by GO:0005515 protein binding. The olfactory receptor family signatures (IPR050402 and IPR000725) indicate that the ligand class is volatile or amphipathic odorants and related metabolites; binding of such ligands stabilizes an active GPCR conformation that recruits and activates G proteins.\n\nFrom this molecular function, the biological process follows. GPCR activation modulates second messengers (cAMP, cGMP, Ca2+), which in turn regulate transcriptional and cytoskeletal programs that tune cell division and survival pathways. Such signaling cascades provide a mechanistic route to GO:0042127 regulation of cell population proliferation: chemosensory input from this receptor class can bias proliferative outputs in epithelial and immune contexts by altering MAPK and PI3K pathways downstream of G protein coupling.\n\nThe cellular component is dictated by the 7TM topology and the olfactory GPCR family: a multi-pass membrane receptor that embeds in the lipid bilayer and signals at the cell surface. This places the protein at the GO:0005886 plasma membrane and aligns with the experimentally observed cell membrane localization of multi-pass GPCRs.\n\nMechanistically, I hypothesize that extracellular hydrophobic odorants or endogenous odorant-like lipids enter a transmembrane binding pocket formed by helices III, V, VI, and VII (IPR017452), shifting the equilibrium toward an active state that exposes intracellular coupling surfaces. These surfaces bind heterotrimeric G proteins, triggering GDP-GTP exchange and downstream effector engagement. Likely interaction partners include Gα subunits (e.g., Golf/Gαs), Gβγ dimers, GPCR kinases (GRKs), and arrestins that terminate signaling and direct receptor trafficking. Through these assemblies, the receptor integrates chemosensory cues into intracellular pathways that can influence proliferation and membrane-proximal signaling hubs.","category":"dark","control_evaluation":null,"validation_plan":null,"structure":{"source":"AlphaFold DB","pdb":"/structures/AF-Q8NH64.pdb","alphafold":"https://alphafold.ebi.ac.uk/entry/Q8NH64"},"links":{"uniprot":"https://www.uniprot.org/uniprotkb/Q8NH64/entry","atlas":"/p/Q8NH64"},"provenance":{"model":"BioReason-Pro (ESM3 esm3-sm-open-v1)","source_list":"Pharos Tdark","note":"AI prediction, not experimentally verified"}}