Ubiquinol oxidase subunit III subfamily. Ubiquinol oxidase, the terminal oxidase in the respiratory chains of aerobic bacteria, is a multi-chain transmembrane protein located in the cell membrane. It catalyzes the reduction of O2 and simultaneously pumps protons across the membrane. Ubiquinol oxidases feature four subunits in contrast to the 13 subunit bovine cytochrome c oxidase (CcO). Subunits I, II, and III of bovine CcO are encoded within the mitochondrial genome and the remaining 10 subunits are encoded within the nuclear genome. Subunits I, II and III of ubiquinol oxidase are homologous to the corresponding subunits in bovine CcO. Although not required for catalytic activity, subunit III appears to be involved in assembly of the multimer complex.
Jiyao W et al.(2023). "The conserved domain database in 2023.",