Comparative study of the primary structures of cytochrome b5 from four species

The primary structures of human, bovine, and chicken cytochrome b(5) have been determined and compared with that of the previously studied rabbit protein. One peptide containing 31 amino acid residues and another containing 10 were found common to all four species. The substitutions of amino acids between species could be accounted for mainly by single base exchange, with a few exceptional double base exchanges for the chicken. Results for bovine cytochrome b(5) differ significantly from those previously reported for calf cytochrome b(5).