Cytochrome C Oxidase Subunit III (COX3)

Cytochrome c oxidase subunit III is one of main transmembrane subunits of cytochrome c oxidase. Cytochrome c oxidase is an oligomeric enzymatic complex that is located in the mitochondrial inner membrane of eukaryotes and in the plasma membrane of aerobic prokaryotes. The core structure of prokaryotic and eukaryotic cytochrome c oxidase contains three common subunits, I, II and III. In prokaryotes, subunits I and III can be fused and a fourth subunit is sometimes found, whereas in eukaryotes there are a variable number of additional small subunits.

As the bacterial respiratory systems are branched, they have a number of distinct terminal oxidases, rather than the single cytochrome c oxidase present in the eukaryotic mitochondrial systems.