{"uniprot":"Q8TF08","gene":"COX7B2","name":"Cytochrome c oxidase subunit 7B2, mitochondrial","organism":"Homo sapiens (Human)","status":"dark","length":81,"sequence":"MMFPLARNALSSLKIQSILQSMARHSHVKHSPDFHDKYGNAVLASGTAFCVATWVFTATQIGIEWNLSPVGRVTPKEWKHQ","function_summary":"A small single-pass membrane subunit of human cytochrome c oxidase that stabilizes the architecture of the terminal oxidase in the mitochondrial inner membrane. By forming a rigid scaffold that binds neighboring subunits, it sustains efficient electron transfer from cytochrome c to oxygen and preserves the coupling that drives proton translocation during oxidative phosphorylation. This structural role supports cellular energy production and indirectly underpins neurodevelopmental pathways that depend on mitochondrial respiration.","plain_language":"COX7B2 has barely been studied. The model's best guess: A small single-pass membrane subunit of human cytochrome c oxidase that stabilizes the architecture of the terminal oxidase in the mitochondrial inner membrane. By forming a rigid scaffold that binds neighboring subunits, it sustains efficient electron transfer from cytochrome c to oxygen and preserves the coupling that drives proton translocation during oxidative phosphorylation.","uniprot_summary":"Component of the cytochrome c oxidase complex (mitochondrial respiratory chain complex IV) that catalyzes the reduction of oxygen to water. Electrons originating from reduced cytochrome c in the intermembrane space are transferred via the binuclear center formed by heme A3 and copper B (Ref.2).","go_terms":{"molecular_function":[{"id":"GO:0005515","label":"protein binding"},{"id":"GO:0004129","label":"cytochrome-c oxidase activity"}],"biological_process":[{"id":"GO:0007417","label":"central nervous system development"}],"cellular_component":[{"id":"GO:0005751","label":"mitochondrial respiratory chain complex IV"}]},"interpro":[{"id":"IPR023272","name":"Cytochrome C oxidase, subunit VIIB domain superfamily","type":"homologous_superfamily","start":26,"end":81},{"id":"IPR008433","name":"Cytochrome C oxidase, subunit VIIB","type":"family","start":1,"end":81}],"reasoning":"I begin with the InterPro architecture. The sequence is fully covered by IPR008433 (Cytochrome C oxidase, subunit VIIB family, residues 1–81), and its core is reinforced by IPR023272 (Cytochrome C oxidase, subunit VIIB domain superfamily, residues 26–81). This compact, largely helical subunit-VIIb fold is characteristic of a small, single-pass membrane protein that packs against other cytochrome c oxidase subunits. The N-to-C arrangement—an N-terminal family-defining region that continues into a conserved superfamily core—creates a rigid scaffold that stabilizes the holoenzyme rather than catalyzing chemistry directly. Such a scaffold inherently mediates multivalent contacts with neighboring polypeptides, which causally supports GO:0005515 protein binding as a primary molecular function.\n\nFrom this scaffold, I infer the molecular function of the assembled complex. Although subunit VIIB is non-catalytic, its architecture is indispensable for the operation of cytochrome c oxidase. By buttressing the transmembrane core and shaping the quaternary arrangement that channels electrons from cytochrome c via the CuA center and heme A to the binuclear heme a3–CuB center, this subunit enables GO:0004129 cytochrome-c oxidase activity at the level of the intact complex. The complex consumes O2 and reduces it to water while coupling to proton translocation; subunit VIIB’s structural role is necessary for this chemistry and its membrane-coupled energetics.\n\nThis molecular function feeds directly into broader biological processes. By sustaining efficient oxidative phosphorylation within complex IV, the protein supports ATP production and mitochondrial membrane potential formation. In multicellular organisms, robust mitochondrial respiration is a prerequisite for neurodevelopmental pathways; thus, the structural contribution of subunit VIIB propagates to GO:0007417 central nervous system development through energy and redox homeostasis.\n\nThe cellular context follows from the fold and function. A single-pass hydrophobic segment and a compact extramembrane domain position the protein in the mitochondrial inner membrane as part of the cytochrome c oxidase assembly. This places it squarely within GO:0005751 mitochondrial respiratory chain complex IV and, by extension, the inner membrane environment where the proton-motive force is generated and utilized.\n\nMechanistically, I hypothesize that subunit VIIB forms a stabilizing strut that couples the catalytic core (subunits I–III) to peripheral subunits (V–VI), tuning electron transfer pathways and the proton-pumping conformational cycle. It likely binds neighboring subunits such as COX6 and COX8 to maintain the geometry of the CuA-to-heme conduit and to secure the assembly against thermal fluctuations. Consequently, its interaction network should include core complex IV components and assembly factors that chaperone or mature the enzyme within the inner membrane.","category":"dark","control_evaluation":null,"validation_plan":null,"structure":{"source":"AlphaFold DB","pdb":"/structures/AF-Q8TF08.pdb","alphafold":"https://alphafold.ebi.ac.uk/entry/Q8TF08"},"links":{"uniprot":"https://www.uniprot.org/uniprotkb/Q8TF08/entry","atlas":"/p/Q8TF08"},"provenance":{"model":"BioReason-Pro (ESM3 esm3-sm-open-v1)","source_list":"Pharos Tdark","note":"AI prediction, not experimentally verified"}}