Cytochrome c oxidase (COX) is a multi-subunit enzyme complex that catalyses the final step of electron transfer through the respiratory chain on the mitochondrial inner membrane. This family is composed of cytochrome c oxidase subunit 4 from prokaryotes.

1: The whole structure of the 13-subunit oxidized cytochrome c oxidase at 2.8 A. Tsukihara T, Aoyama H, Yamashita E, Tomizaki T, Yamaguchi H, Shinzawa-Itoh K, Nakashima R, Yaono R, Yoshikawa S; Science 1996;272:1136-1144. PMID:8638158