α-Chain sequence of newt haemoglobin (taricha granulosa)

The amino acid sequence of the α-chain of the major haemoglobin of a newt, T. granulosa, has been determined. The chain is 142 residues long and has an extra methionine at its N-terminus when compared with human α-chain. Most of the tryptic peptides were sequenced by a combination of the subtractive Edman method and by deduction from the compositions of overlapping fragments produced by various enzymic treatments. The sequence of two 'core' regions was obtained by automatic sequencing of large peptides produced by trypsin cleavage at arginine residues only after blockage of lysine residues by citraconylation; by cleavage between aspartic acid and proline residues with 70% formic acid, and by cyanogen bromide cleavage at methionine residues. The sequence of T. granulosa α-chain is compared with those of representative species from the other classes of vertebrates. The differences in α-chain between the classes of vertebrates are compared with the differences in this protein between an equal number of orders of mammals. This comparison allows us to conclude that the major functional and conformational features of α-chain have been conserved since the divergence of the classes of jawed vertebrates.