Structural adaptation of bird hemoglobins to high-altitude respiration and the primary sequences of black-headed gull (Larus ridibundus, Charadriiformes) alpha A- and beta/beta'-chains

Two hemoglobin components HbA (alpha A2 beta 2) and (alpha D2 beta 2) have been detected by analytical electrophoresis in the lysed erythrocytes of the adult Black-Headed Gull (Larus ridibundus). We report the complete primary structure of the alpha A- and beta-chains of the major hemoglobin component HbA. Following the chain separation and isolation of the tryptic peptides by RP-HPLC, the amino-acid sequence was established by automatic Edman degradation in spinning cup and gas-phase sequencers. The primary structures of alpha A- and beta-chains from the Black-Headed Gull HbA differ by 11 and by 6 amino-acid residues from the corresponding chains of Greylag Goose. These changes are randomly distributed over both alpha-helical and interhelical regions. The presence of beta/beta'-chains is indicated by the observation of Ile/Leu at position beta 78. An exchange at position beta 55 (D6)Leu-Asn which is known to be involved in the alpha 1 beta 1-interface with alpha 119(H2)Pro has been found. It is suggested that packing contacts in the alpha 1 beta 1-interface are important for high altitude respiration in birds.