Cytochrome c oxidase is the last enzyme in the respiratory electron transport chain of mitochondria and it is also called Complex IV. Cytochrome c oxidase 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 higher plants mitochondria, Complex IV processes 14 subunits. COX X1 (AT5G27760/AT3G05550) is one subunit of the Complex IV.
