Functional effects of heme orientational disorder in sperm whale myoglobin.

摘要: The optical absorption and ligand binding properties of newly reconstituted sperm whale myoglobin were examined systematically at pH 8, 20 degrees C. conventional absorbance magnetic circular dichroism spectra freshly samples identical to those the native protein. In contrast, azide or CO initially exhibited less in Soret wavelength region than myoglobin. These data support theory proposed by La Mar co-workers (La Mar, G. N., Davis, N. L., Parish, D. W., Smith, R. M. (1983) J. Mol. Biol. 168, 887-896) that protoheme inserts into apomyoglobin two distinct orientations. equilibrium kinetic parameters for O2 observed be Thus, orientation heme group has no effect on physiological This result is disagreement with preliminary report Livingston et al. (Livingston, J., Brown, W. (1984) Am. Chem. Soc. 106, 3025-3026) which suggested abnormal conformation a 10-fold greater affinity association rate constant binding. Significant heterogeneity was only long-chain isonitrile myoglobin, even these cases, constants normal conformations differed factor 4.