Crystal structure of oxygenated Scapharca dimeric hemoglobin at 1.7-A resolution

• Main Authors: Condon, Peter J., Royer, William E.
• Other Authors: Department of Biochemistry and Molecular Pharmacology, Program in Molecular Medicine
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2022
• Subjects: Animals; Binding Sites; Bivalvia; Computer Simulation; Crystallography; X-Ray; Heme; Hemoglobins; Ligands; Models; Molecular; Oxyhemoglobins; Protein Conformation; Water; Life Sciences; Medicine and Health Sciences; Sperm whale
• Online Access: https://hdl.handle.net/20.500.14038/42471; https://escholarship.umassmed.edu/oapubs/817

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.