Cytochrome c oxidase (COX) is the terminal   enzyme of the mitochondrial respiratory chain. It is a multi-subunit enzyme   complex that couples the transfer of electrons from cytochrome c to molecular   oxygen and contributes to a proton electrochemical gradient across the inner   mitochondrial membrane. The complex consists of 13 mitochondrial- and   nuclear-encoded subunits.   COX4I1, also   named as COX4 and COXIV-1, is one of the nuclear-coded polypeptide chains of   cytochrome c oxidase, the terminal oxidase in mitochondrial electron   transport. 

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