title: Structure of Greyhound hemoglobin: origin of high oxygen affinity.
abstract: This study presents the crystal structure of Greyhound hemoglobin (GrHb) determined to 1.9 Å resolution. GrHb was found to crystallize with an α₁β₁ dimer in the asymmetric unit and belongs to the R2 state. Oxygen-affinity measurements combined with the fact that GrHb crystallizes in the R2 state despite the high-salt conditions used for crystallization strongly indicate that GrHb can serve as a model high-oxygen-affinity hemoglobin (Hb) for higher mammals, especially humans. Structural analysis of GrHb and its comparison with the R2-state of human Hb revealed several regions that can potentially contribute to the high oxygen affinity of GrHb and serve to rationalize the additional stability of the R2-state of GrHb. A previously well studied hydrophobic cluster of bar-headed goose Hb near α119 was also incorporated in the comparison between GrHb and human Hb. Finally, a structural comparison with generic dog Hb and maned wolf Hb was conducted, revealing that in contrast to GrHb these structures belong to the R state of Hb and raising the intriguing possibility of an additional allosteric factor co-purifying with GrHb that can modulate its quaternary structure.
authors.affiliation: Biophysics Graduate Program, The Ohio State University, Columbus, OH 43210, USA.
authors.forename: Veer S
authors.initials: VS
authors.lastname: Bhatt
authors.forename: Sara
authors.initials: S
authors.lastname: Zaldívar-López
authors.forename: David R
authors.initials: DR
authors.lastname: Harris
authors.forename: C Guillermo
authors.initials: CG
authors.lastname: Couto
authors.forename: Peng G
authors.initials: PG
authors.lastname: Wang
authors.forename: Andre F
authors.initials: AF
authors.lastname: Palmer
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D018360:Crystallography, X-Ray; D004285:Dogs / Q000378:metabolism*; D006441:Hemoglobin A / Q000737:chemistry* / Q000378:metabolism*; D006801:Humans; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010100:Oxygen / Q000378:metabolism*; D011487:Protein Conformation; D055503:Protein Multimerization; D020836:Protein Structure, Quaternary; D016415:Sequence Alignment
chemical_list: D006441:Hemoglobin A; D010100:Oxygen