Studies on cytochrome c oxidase, II. The chemical constitution of a short polypeptide from the beef heart enzyme.

A low molecular weight (approximately 6000) polypeptide fraction was isolated from beef heart cytochrome c oxidase, consisting of three peptides with the N-terminal end groups isoleucine, phenylalanine and serine. The complete amino acid sequence of the serine component is described. From the chemical constitution, a site-specific cleavage from a precursor protein and a possible function in membrane penetration and complex formation of the oxidase is inferred.