Studies on cytochrome c oxidase, IV[1--3]. Primary structure and function of subunit II.

The amino acid sequence of polypeptide II from beef heart cytochrome c oxidase is described. Comparision of this primary structure with those of azurins, plastocyanins and stellacyanins reveals clear homologies among them. Thus subunit II of the oxidase is a member of this copper protein family. The sequence homology indicates a copper binding site consisting of two invariant histidines and two sulfur-containing amino acids. Thus subunit II is like a blue copper protein with type I copper.