Component of the cytochrome c oxidase, the last enzyme in themitochondrial electron transport chain which drives oxidativephosphorylation. The respiratory chain contains 3 multisubunitcomplexes succinate dehydrogenase (complex II, CII), ubiquinol-cytochrome c oxidoreductase (cytochrome b-c1 complex, complex III, CIII) and cytochrome c oxidase (complex IV, CIV), that cooperate totransfer electrons derived from NADH and succinate to molecular oxygen, creating an electrochemical gradient over the inner membrane thatdrives transmembrane transport and the ATP synthase. Cytochrome coxidase is the component of the respiratory chain that catalyzes thereduction of oxygen to water. Electrons originating from reducedcytochrome c in the intermembrane space (IMS) are transferred via thedinuclear copper A center (CU (A) ) of subunit 2 and heme A of subunit 1to the active site in subunit 1, a binuclear center (BNC) formed byheme A3 and copper B (CU (B) ). The BNC reduces molecular oxygen to 2water molecules using 4 electrons from cytochrome c in the IMS and 4protons from the mitochondrial matrix.

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