Crystallographic analysis of synechocystis cyanoglobin reveals the structural changes accompanying ligand binding in a hexacoordinate hemoglobin.Trent III, J.T., Kundu, S., Hoy, J.A., Hargrove, M.S.
(2004) J.Mol.Biol. 341: 1097-1108
- PubMed: 15289104
- DOI: 10.1016/j.jmb.2004.05.070
- Primary Citation of Related Structures:  1S6A
- PubMed Abstract:
The crystal structures of cyanide and azide-bound forms of the truncated hemoglobin from Synechocystis are presented at 1.8 angstroms resolution. A comparison with the structure of the endogenously liganded protein reveals a conformational shift unpr ...
The crystal structures of cyanide and azide-bound forms of the truncated hemoglobin from Synechocystis are presented at 1.8 angstroms resolution. A comparison with the structure of the endogenously liganded protein reveals a conformational shift unprecedented in hemoglobins, and provides the first picture of a hexacoordinate hemoglobin in both the bis-histidyl and the exogenously coordinated states. The structural changes between the different conformations are confined to two regions of the protein; the B helix, and the E helix, including the EF loop. A molecular "hinge" controlling movement of the E helix is observed in the EF loop, which is composed of three principal structural elements: Arg64, the heme-d-propionate, and a three-residue extension of the F helix. Additional features of the structural transition between the two protein conformations are discussed as they relate to the complex ligand-binding behavior observed in hexacoordinate hemoglobins, and the potential physiological function of this class of proteins.
Department of Biochemistry, Biophysics and Molecular Biology, Iowa State University, Ames, IA 50010, USA.