Studies on CytochromecOxidase, VI. Polypeptide IV. The Complete Primary Structure

Abstract

The complete primary structure of the cytoplasmically synthesized polypeptide IV from beef heart cytochrome oxidase was determined via isolation and sequencing of overlapping methionine, tryptophan and arginine fragments. The protein consists of 147 amino acids (MW 17,153). It is characterized as a part of a membrane protein complex by a hydrophobic segment consisting of 19 residues. This segment probably contacts the lipids of the inner mitochondrial membrane. Additional specific contacts may result from pairwise formation of salt bridges between ionic groups of the protein and the phospholipids. The function of this component of the terminal oxidase is yet unknown.