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Title
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Crystal structure of photolysed carbonmonoxy-myoglobin.
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Authors
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I.Schlichting,
J.Berendzen,
G.N.Phillips,
R.M.Sweet.
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Ref.
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Nature, 1994,
371,
808-812.
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PubMed id
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Abstract
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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.
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