Proton resonance assignments and ligand exchange kinetics in high-spin and mixed-spin myoglobin complexes using two-dimensional exchange spectroscopy.
The task of assigning resonances in proton nuclear magnetic resonance spectra of paramagnetic heme proteins can be an arduous process, but with the development of multi-dimensional NMR methods the situation has improved. It is demonstrated here that two-dimensional exchange spectroscopic experiments can be used to obtain to assignment correlations for the heme protons of methydroxy-, metthiocyano-, metaquo-, and metimidazole-myoglobin forms. All the assignments are unambiguous and straightforward when the temperature and mixing times are adjusted to minimize nuclear Overhauser cross-peaks from each complex. Moreover, saturation transfer experiments allow the study of ligand binding kinetics. The exchange rates between metaquo- and metimidazole- (or methyl substituted imidazole) myoglobin complexes are estimated. The differences between the exchange rates reflect differences in the hydrophobic and steric interactions between the ligands and the protein moiety.
Luo
Y
Y
Department of Chemistry, Portland State University, P.O. Box 751, Portland, OR 97207-0751, USA.
Peyton
D H
DH
Yee
S
S
D000818:Animals; D006736:Horses; D007093:Imidazoles / Q000737:chemistry; D009211:Myoglobin / Q000737:chemistry*; D019906:Nuclear Magnetic Resonance, Biomolecular / Q000379:methods; D013861:Thiocyanates / Q000737:chemistry; D014867:Water / Q000737:chemistry
D007093:Imidazoles; D009211:Myoglobin; D013861:Thiocyanates; D014867:Water; C029899:imidazole; C018100:1-methylimidazole; C023439:4-methylimidazole; C009941:potassium thiocyanate