Haemoglobins of the Shark, Heterodontus Portusjacksoni II. Amino Acid Sequence of the a-Chain

Abstract

The amino acid sequence of the a-chain of the principal haemoglobin from the shark, H. portusjacksoni has been determined. The chain has 148 residues and is acetylated at the amino terminal. The soluble peptides obtained by tryptic and chymotryptic digestion of the protein or its cyanogen bromide fragments were isolated by gel filtration, paper ionophoresis and paper chromatography. The amino acid sequences were determined by the dansyl-Edman procedure. The insoluble 'core' peptide from the tryptic digestion contained 34 residues and required cleavage by several proteases before the sequence was established. Compared with human a-chain there are 88 amino acid differences including the additional seven residues which appear on the amino terminal of the shark chain. There is also one deletion and one insertion. The chain contains no tryptophan but has four cysteinyl residues which is the highest number of such residues recorded for a vertebrate globin.