Located in the inner mitochondrial membrane, cytochrome c oxidase is the third and final proton-pumping protein of the electron transport chain.
Electrons flow through the enzyme and are accepted by oxygen.
The oxygen which has a high affinity for electrons is reduced to produce water. During this process, protons are pumped outside to the intermembrane space from the matrix. The importance of cytochrome c oxidase is its role as a thermodynamic force for oxidative phosphorylation and its ability to contain dangerous partially reduced intermediates, superoxides, which can cause genetic and tissue damage. This webpage focuses on the structure function relationship of mammalian cytochrome c oxidase. Yet amino acid residues and structures between mammals and bacteria are highly conserved allowing bacteria cytochrome c oxidase to be studied for the structure function relationship.