Amino Acid Sequence of the Globin lIB Chain of the Dimeric Haemoglobin of the Bivalve Mollusc Andara trapezia

Abstract

The tryptic peptides of the S-carboxymethylated globin chain ofa dimeric haemoglobin from A. trapezia were purified by high-performance liquid chromatography and their amino acid sequences determined by the dansyl-Edman method.The cyanogen bromide fragments were purified or digested with chymotrypsin to give overlap fragments which were sequenced by similar methods.In conjunction with some sequences of larger peptides derived by digestion with staphylococal protease, the complete sequence of 146 residues was deduced. The sequence has been compared with that previously determined for the 153 residue a-chain of the tetrameric haemoglobin from the same mollusc and shows 45% identity. In the E and F helical regions the homology is particularly noticeable with 75 and 100% identity respectively. The sequence of the dimeric haemoglobin chain of A. trazezia is very homologous (90% identity) to the published sequence of the similar haemoglobin from A. broughtonU. The homology when compared with other globin chains is much less, with approximately 20% identity in amino acid sequence.

Genetic Variation of the Dimeric Haemoglobin of the Bivalve Mollusc Anadara trapezia

“…The peptide map for SCM-globins lIb was reported in the supplementary material to a previous paper (Fisher et al 1984). When samples of SCM-globin IIa were mapped in parallel with SCM-globin lIb, almost identical peptide patterns were obtained after developing with ninhydrin.…”

“…The presence of those composite peptides assists in the comparison of the sequences of globin IIa and lIb since it indicates that it is the same basic residue in each case, and that there has been no deletion of a residue. In the case of globin lIb the composite peptides Tp(l + 2), Tp(2 + 3), Tp(5 + 6), Tp(l3 + 14) were reported (Fisher et al 1984). In the comparative examination of globin IIa and lIb, Tp(7 + 8), Tp(l5 + 16), Tp(l6 + 17) and Tp(l8 + 19) were also detected.…”

“…Subsequent work on the amino acid sequence of globin lIb (Fisher et al 1984) showed that there were 15 residues of lysine, 20 residues of aspartic acid and 11 residues of glycine. The analytical value extrapolated for serine (8' 3) gave one residue less than the amino acid sequence (9 residues) required.…”

“…Tryptic or other enzyme digests were fractionated by peptide mapping using paper ionophoresischromatography (10-15 mg) or high-performance liquid chromatography as described previously (Fisher et al 1984), and identified by amino acid analysis and N-terminal residue determination in comparison with pep tides known from the previous work on HbIIb (Fisher et al 1984). For efficient tryptic digestion, the globins were dissolved in 8 M urea-I % (w/v) NH4HC03 and diluted to 2 M urea before adding the trypsin.…”

“…The amino acid sequence of the 153 residues of the ct-chain (Como and Thompson 1980b), the 151 residues of the {3-chain (Gilbert and Thompson 1985) and the 146 residues of the globin lIb chain (Fisher et al 1984) have been reported. Dimeric as well as tetrameric haemoglobins have been found in other arcid molluscs, and the amino acid sequence of the dimeric globin from A. broughtonii (Furuta and Kajita 1983) and from Scapharca inaequivalvis (Petruzzelli et al 1985) have been determined.…”