title: Crystal structure of oxygenated Scapharca dimeric hemoglobin at 1.7-A resolution.
abstract: The crystal structure of the cooperative dimeric hemoglobin from the blood clam Scapharca inaequivalvis has been determined in the oxygenated state and refined to an R-factor of 0.157 at 1.7-A resolution. The structure is very similar to the carbon monoxide-liganded form with subtle differences in ligand binding geometry. Oxygen binds to the heme iron in a bent conformation with Fe-O-O angles of 135 degrees and 150 degrees for the two subunits. These observed angles are lower than the equivalent angles in the carbon monoxide-liganded form and intermediate between the angles observed in structures of oxygenated sperm whale myoglobin and oxygenated human hemoglobin. This third high resolution structure of Scapharca dimeric hemoglobin permits a detailed analysis of the water structure in the highly hydrated interface between subunits.
authors.affiliation: Program in Molecular Medicine, University of Massachusetts Medical Center, Worcester 01605.
authors.forename: P J
authors.initials: PJ
authors.lastname: Condon
authors.forename: W E
authors.initials: WE
authors.lastname: Royer
mesh_terms: D000818:Animals; D001665:Binding Sites; D049872:Bivalvia / Q000737:chemistry*; D003198:Computer Simulation; D018360:Crystallography, X-Ray; D006418:Heme / Q000737:chemistry; D006454:Hemoglobins / Q000737:chemistry*; D008024:Ligands; D008958:Models, Molecular; D010108:Oxyhemoglobins / Q000737:chemistry*; D011487:Protein Conformation; D014867:Water / Q000737:chemistry
chemical_list: D006454:Hemoglobins; D008024:Ligands; D010108:Oxyhemoglobins; D014867:Water; C083082:dimeric hemoglobin, Scapharca inaequivalvis; D006418:Heme