Primary structure of the minor haemoglobins from the sea lamprey (Petromyzon marinus, Cyclostomata).

Erythrocytes of the adult Sea Lamprey Petromyzon marinus contain several haemoglobin species, but only the main constituent has hitherto been sequenced. The present paper describes the determination of the primary structures of the two minor species, whose electrophoretic mobilities are higher and lower than that of the main component. Tryptic peptides from both chains were purified by high-performance liquid chromatography, then sequenced and aligned by homology with the main haemoglobin. The fast and the major components appeared to be very similar, differing in only four positions (pos. 5: Ser----Thr; pos. 33: Thr----Ser; pos. 86: Val----Ala; pos. 99: Gly----Arg). The slow haemoglobin component, however, differed from the main component with respect to 27 amino-acid residues. The position of the three globins of Petromyzon marinus in the phylogenetic tree of haemoglobins is discussed and a relationship with primitive alpha-chains is postulated.