Cytochrome C Oxidase

Family:
Gene Family: Mitochondrial complex IV: cytochrome c oxidase subunits (COX, MT-CO)

Structure:
The complex is a large integral membrane protein composed of several metal prosthetic sites and 14 protein subunits in mammals. Here, eleven subunits are nuclear in origin, and three are synthesized in the mitochondria. The complex contains two hemes, a cytochrome a and cytochrome a3, and two copper centers, the CuA and CuB centers.

Function:
The enzyme cytochrome c oxidase or electron transport chain (ETC) Complex IV is a large transmembrane protein complex found in bacteria and the mitochondrial membrane of eukaryotes. It receives an electron from each of four cytochrome c molecules, and transfers them to one oxygen molecule, converting molecular oxygen to two molecules of water. In the process, it binds four protons from the inner aqueous phase to make water and in addition translocates four protons across the membrane, in the process, helping to establish a transmembrane difference of proton electrochemical potential that the ATP synthase then uses to synthesize ATP.
Reaction: 4 Fe²⁺-cytochrome c + 8 H⁺_in + O₂ → 4 Fe³⁺-cytochrome c + 2 H₂O + 4 H⁺_out