Heterogeneity of amino acid sequence in hippopotamus cytochrome c.
The amino acid sequences of chymotryptic and tryptic peptides of Hippopotamus amphibius cytochrome c were determined by a recent modification of the manual Edman sequential degradation procedure. They were ordered by comparison with the structure of the hog protein. The hippopotamus protein differs in three positions: serine, alanine, and glutamine replace alanine, glutamic acid, and lysine in positions 43, 92, and 100, respectively. Since the artiodactyl suborders diverged in the mid-Eocene some 50 million years ago, the fact that representatives of some of them show no differences in their cytochromes c (cow, sheep, and hog), while another exhibits as many as three such differences, verifies that even in relatively closely related lines of descent the rate at which cytochrome c changes in the course of evolution is not constant. Furthermore, 10.6% of the hippopotamus cytochrome c preparation was shown to contain isoleucine instead of valine at position 3, indicating that one of the four animals from which the protein was obtained was heterozygous in the cytochrome c gene. Such heterogeneity is a necessary condition of evolutionary variation and has not been previously observed in the cytochrome c of a wild mammalian population.
D000595:Amino Acid Sequence; D000818:Animals; D001188:Artiodactyla; D002918:Chymotrypsin; D003574:Cytochrome c Group; D010446:Peptide Fragments / Q000032:analysis; D013045:Species Specificity; D013552:Swine; D014357:Trypsin
D003574:Cytochrome c Group; D010446:Peptide Fragments; D002918:Chymotrypsin; D014357:Trypsin