High-Altitude Respiration of Geese. The Primary Structures of the Major and Minor Hemoglobin-Components of Adult Andean Goose (Chloephaga melanoptera, Anatidae): the Mutation Leu → Ser in Position 55 of the ß-Chains

Abstract

The primary structures of the hemoglobin components Hb A and Hb D of the adult Andean Goose (Chloephaga melanoptera) are presented. The globin chains were separated on CM-Cellulose in 8M urea buffer. The amino-acid sequences were established by automatic Edman degradation of the globin chains and of the tryptic peptides in liquid- and gas-phase sequenators. The sequences are aligned with those of Greylag Goose (Anser anser) as a biological reference and other sequences of birds. A detailed evaluation of all residues of Andean Goose hemoglobins on the basis of the 12000 known avian globin sequences leads to a molecular pattern for high-altitude respiration of geese. The replacement of functional and structural importance is the unique occurrence of the residue .beta.55 Leu .fwdarw. Ser (all other exchanges are functionally neutral), interrupting the same .alpha.1 .beta.1-interface contact (.alpha.119-.beta.55) that accounts for high-altitude respiration of the Barheaded Goose (Anser indicus); there the mutation is found on .alpha.A 119. Loosening the constraints of this interface must be interpreted as a destabilization of the low-affinity T-structure in favour of the high-affinity R-structure. The structural and functional significance of this interface for the molecular biology of high-altitude respiration of the Andean Goose and Barheaded Goose is discussed. Since Hb A consists of .alpha.2A.beta.2 and Hb D consists of .alpha.2D.beta.2 the mutation occurring in blood of the Andean Goose affects both hemoglobins whereas in the case of the Barheaded Goose only Hb A is affected. These results show that Hb D can be considered a biological reserve to enlarge situatively the normal hemoglobin function. A general molecular pattern for permanent (selective advantage of high intrinsic oxygen affinity) and transitory (selective advantage of graded oxygen affinities) adaptation to hypoxia is discussed. A survey on the sequence homology of the globin chaines of geese (Anserinae) and ducks (Anatinae) is given.