title: Crystal structure of photolysed carbonmonoxy-myoglobin.
abstract: Myoglobin is a globular haem protein that reversibly binds ligands such as O2 and CO. Single photons of visible light can break the covalent bond between CO and the haem iron in carbon-monoxy-myoglobin (MbCO) and thus form an unstable intermediate, Mb*CO, with the CO inside the protein. The ensuing rebinding process has been extensively studied as a model for the interplay of dynamics, structure and function in protein reactions. We have used X-ray crystallography at liquid-helium temperatures to determine the structure of Mb*CO to a resolution of 1.5 A. The photodissociated CO lies on top of the haem pyrrole ring C. Comparison with the CO-bound and unligated myoglobin structures reveals that on photodissociation of the CO, the haem 'domes', the iron moves partially out of the haem plane, the iron-proximal histidine bonds is compressed, the F helix is strained and the distal histidine swings towards the outside of the ligand-binding pocket.
authors.affiliation: Department of Biophysics, Max Planck Institute for Medical Research, Heidelberg, Germany.
authors.forename: I
authors.initials: I
authors.lastname: Schlichting
authors.forename: J
authors.initials: J
authors.lastname: Berendzen
authors.forename: G N
authors.initials: GN
authors.lastname: Phillips
authors.forename: R M
authors.initials: RM
authors.lastname: Sweet
mesh_terms: D000818:Animals; D001665:Binding Sites; D018360:Crystallography, X-Ray; D009211:Myoglobin / Q000737:chemistry*; D010782:Photolysis; D011487:Protein Conformation; D014907:Whales
chemical_list: D009211:Myoglobin; C018013:carboxymyoglobin