Ion Binding Properties of Calbindin D9k—A Monte Carlo Simulation Study

Abstract

Monte Carlo simulations are used to calculate the binding constant of two Ca2+ ions to the protein calbindin D9k. The change in binding constant with respect to mutation of charged amino acids, presence of various electrolytes, protein concentration, solution pH and competitive binding by monovalent ions is investigated. Each of these factors may have large influence on the binding constant. The simulations are performed in a dielectric continuum model, the so-called primitive model of electrolyte theory, with a fixed proteinstructure and a uniform dielectric permittivity. The calculated binding constants are in excellent agreement with available experiments data, and describe changes in the binding constant over five orders of magnitude.