Crystal structure of photolysed carbonmonoxy-myoglobin.
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.
Schlichting
I
I
Department of Biophysics, Max Planck Institute for Medical Research, Heidelberg, Germany.
Berendzen
J
J
Phillips
G N
GN
Sweet
R M
RM
D000818:Animals; D001665:Binding Sites; D018360:Crystallography, X-Ray; D009211:Myoglobin / Q000737:chemistry*; D010782:Photolysis; D011487:Protein Conformation; D014907:Whales
D009211:Myoglobin; C018013:carboxymyoglobin