Molecular basis of bird respiration: primary hemoglobin structure component from Tufted duck (Aythya fuligula, Anseriformes)--role of alpha99Arg in formation of a complex salt bridge network.
The primary structure of the major hemoglobin component, HbA (alpha(A)- and beta-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 alpha99Arg and beta101Glu to emerge as a new intersubunit contact site not found in the hemoglobin structure of any other species. alpha99Arg forms a complex salt bridge network involving alpha99Arg-beta101Glu-beta104Arg-beta108Asp. Also the substitution at alpha34 --> Ile, alpha38 --> Gln and beta55 --> Leu serves to stabilize the oxy-structure, leading to higher oxygen affinity.
Abbasi
Atiya
A
International Centre for Chemical Sciences, University of Karachi, Karachi, 75270, Pakistan. abbasi@global.net.pk
Lutfullah
Ghosia
G
D000596:Amino Acids / Q000032:analysis; D000818:Animals; D001665:Binding Sites / Q000502:physiology; D002851:Chromatography, High Pressure Liquid; D003198:Computer Simulation; D004372:Ducks; D004591:Electrophoresis, Polyacrylamide Gel; D005777:Geese; D006441:Hemoglobin A / Q000737:chemistry* / Q000378:metabolism*; D046911:Macromolecular Substances; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010802:Phylogeny; D017434:Protein Structure, Tertiary; D021122:Protein Subunits; D012119:Respiration; D012492:Salts / Q000737:chemistry*; D020539:Sequence Analysis, Protein; D017386:Sequence Homology, Amino Acid; D013045:Species Specificity; D021241:Spectrometry, Mass, Electrospray Ionization; D013329:Structure-Activity Relationship
D000596:Amino Acids; D046911:Macromolecular Substances; D021122:Protein Subunits; D012492:Salts; D006441:Hemoglobin A