Proton NMR study of the influence on iron oxidation/ligation/spin state on the heme orientational preference in myoglobin.
Proton nuclear magnetic resonance spectroscopy has been utilized to demonstrate that the degree of heme orientational disorder within a given myoglobin protein matrix can be a sensitive function of the oxidation/ligation/spin state of the heme iron. For sperm whale deuterohemin-reconstituted myoglobin, the equilibrium was found to strongly favor (5.7 to 7.8 kJ/mol) the X-ray characterized heme orientation in all six-coordinate states, but with a considerable reduction in preference (to 1.6 kJ/mol) in the five-coordinate deoxy state. In native yellow fin tuna myoglobin, changes in heme orientational preferences of approximately 3 kJ/mol occur even between two six-coordinate ferric states differing solely in spin states.
La Mar
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GN
Department of Chemistry, University of California, Davis 95616.
Smith
W S
WS
Davis
N L
NL
Budd
D L
DL
Levy
M J
MJ
D000818:Animals; D003461:Crystallography; D006418:Heme; D009682:Magnetic Resonance Spectroscopy; D009038:Motion; D009211:Myoglobin; D010084:Oxidation-Reduction; D014907:Whales
D009211:Myoglobin; D006418:Heme