Electrostatic interactions in sperm whale myoglobin. Site specificity, roles in structural elements, and external electrostatic potential distributions

• Published in: The Journal of biological chemistry Vol. 260; no. 26; pp. 14070 - 14082
• Main Authors: Garcia-Moreno, B, Chen, L X, March, K L, Gurd, R S, Gurd, F R
• Format: Journal Article
• Language: English
• Published: Bethesda, MD Elsevier Inc 15-11-1985; American Society for Biochemistry and Molecular Biology
• Subjects: Amino Acids; Animals; Binding Sites; Biological and medical sciences; Chemical Phenomena; Chemistry; Chemistry, Physical; Electrochemistry; Fundamental and applied biological sciences. Psychology; Hydrogen-Ion Concentration; Interactions. Associations; Intermolecular phenomena; Macromolecular Substances; Molecular biophysics; Myoglobin; Protein Conformation; Solvents; Whales; Myoglobin; Site specificity; Sperm whale; Hemoprotein; Solvent accessibility; Electrostatic interaction; PH; Models; Electrostatic potential; Molecular accessibility
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1016/S0021-9258(17)38685-4

The electrostatic free energy contribution to the stability of sperm whale ferrimyoglobin was evaluated according to the static accessibility modified Tanford-Kirkwood model. The electrostatic free energy contribution of each distinct structural element was divided into one term arising from interactions between it and other elements (interelemental) and another from interactions within the particular element itself (intraelemental). At pH 7 the majority of the terms were found to be stabilizing. The interelemental terms are the dominant ones for most structural elements. The small interelemental terms of the C and D helices are compensated by large intraelemental interactions which stabilize these short helices. Perturbations in pH can be accommodated by the structural elements through a redistribution of stabilizing and destabilizing interactions. The electrostatic potentials calculated at the surface of the protein indicate that the internal compensation of local potentials achieved during folding results in a generally neutral protein-solvent interface save for two distinct areas of nonzero potential. The accessibility of each charged atom to solvent was analyzed in terms of the surface area lost to charged, polar and nonpolar atoms separately. The net solvent accessibility lost parallels closely that lost to nonpolar atoms alone, indicating a specific role for nonpolar atoms in defining dielectric shielding of charged atoms, aside from their participation in the well-known hydrophobic interactions.