Abstract

The primary structure of the major hemoglobin component, HbA (αA- and β-chain), from Tufted duck (Aythya fuligula) is presented. The separation of the globin subunits was achieved by ion exchange chromatography on CM-cellulose in 8 M urea. The amino acid sequence was determined by automatic Edman degradation of native chains as well as tryptic and hydrolytic peptides in a gas-phase sequencer. The automated homology model was generated by the protein structure modeling package WHAT IF using the crystal structure coordinates of Bar-headed goose hemoglobin. The 3D structure prediction enables α99Arg and β101Glu to emerge as a new intersubunit contact site not found in the hemoglobin structure of any other species. α99Arg forms a complex salt bridge network involving α99Arg–β101Glu–β104Arg–β108Asp. Also the substitution at α34 → Ile, α38 → Gln and β55 → Leu serves to stabilize the oxy-structure, leading to higher oxygen affinity.

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