Comparison of Myoglobins from Harbor Seal, Porpoise, and Sperm Whale

Abstract

The fully alkylated derivatives of harbor seal and porpoise apomyoglobin have been subjected to chymotryptic hydrolysis. In each case, the products were completely soluble at pH 2.0 in contradistinction to the tryptic hydrolysates. The purified peptides have been subjected to sequence analysis and amide identification and, in conjunction with the tryptic peptides, aligned to produce the complete sequence of each myoglobin. The resulting structures, when compared to the established sperm whale structure, indicate a close similarity among all three proteins. The sperm whale protein differs from that of seal in 26 positions but from that of porpoise in only 15 positions. The seal and porpoise proteins differ at 17 positions. All of the amino acid replacements were confined to 29 positions, leaving 124 of 153 positions in the sequence invariant in the three proteins. The relation of these data to other, partial sequences is discussed.