Cytochrome C oxidase chain VIIb. Cytochrome c oxidase (CcO), the terminal oxidase in the respiratory chains of eukaryotes and most bacteria, is a multi-chain transmembrane protein located in the inner membrane of mitochondria and the cell membrane of prokaryotes. It catalyzes the reduction of O2 and simultaneously pumps protons across the membrane. The number of subunits varies from three to five in bacteria and up to 13 in mammalian mitochondria. Subunits I, II, and III of mammalian CcO are encoded within the mitochondrial genome and the remaining 10 subunits are encoded within the nuclear genome. The VIIb subunit is found only in eukaryotes and its specific function remains unclear. A rare polymorphism of the CcO VIIb gene may be associated with the high risk of nasopharyngeal carcinoma in a Cantonese family.
Jiyao W et al.(2023). "The conserved domain database in 2023.",