NMR study of the molecular and electronic structure of the heme cavity in Dolabella met-cyano myoglobin.
The molecular and electronic structure of the active site of the cyanide-ligated ferric complex of the myoglobin from the mollusc Dolabella auricularia has been investigated using NMR. Analysis of nuclear Overhauser effects has revealed that the correlation times for the internal motion of the heme propionate alpha-CH2 and beta-CH2 groups at ambient temperature are about 5 and 4 ns, respectively. These correlation times indicate that the terminal carboxylate groups of both the heme propionates are not bound to the protein via salt bridges. Although the absence of the propionate-protein interaction does not influence the equilibrium population of the two heme orientational isomers involving rotation about the alpha,gamma-meso axis, it allows the heme to rotate about the iron-His bond in the active site of the myoglobin. Such rotational motion of the heme resulted in an anomalous temperature-dependence of the heme methyl-proton hyperfine shift. Thus the present myoglobin studies provide the first example demonstrating the rotation of the heme about the iron-His bond in native myoglobin.
Department of Biomolecular Engineering, Tokyo Institute of Technology, Japan.
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Yamamoto
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Suzuki
D000818:Animals; D001665:Binding Sites; D006418:Heme / Q000737:chemistry*; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D009682:Magnetic Resonance Spectroscopy; D008786:Metmyoglobin / Q000031:analogs & derivatives* / Q000737:chemistry; D008968:Molecular Conformation; D008974:Mollusca / Q000737:chemistry*; D009587:Nitrogen Isotopes
D009587:Nitrogen Isotopes; C007177:cyanometmyoglobin; D008786:Metmyoglobin; D006418:Heme