Studies on cytochrome c oxidase, VIII. The amino acid sequence of polypeptide VII

The sequence determination of polypeptide VII from beef heart cytochrome c oxidase is described. The amino acid sequence is deduced from overlapping tryptic peptides and peptides obtained after cleavage with Staphylococcus aureus protease. The protein consists of 85 amino acids corresponding to a Mr of 10026, in agreement with a value of 9500 obtained by sodium dodecyl sulfate gel electrophoresis. The amino acid sequence around the only methionine present is very similar to sequences around the invariant heme binding methionine of the cytochrome c family. This similarity suggests that the protein is one of the heme bindings subunits of the oxidase.