Computer Simulation Studies of the Selectivity and Conductance of A Model Calcium Channel

Abstract

Some results of our simulation studies of selectivity and conductance of calcium ion channels in membranes are reported. Ion channels regulate many important physiological functions. To simulate the system we use periodic boundary conditions. We have noted previously that the use of such boundary conditions does not affect our results in any significant manner. The structure of the filter of a calcium channel is reasonably well understood. An important structural element is the set of four glutamate residues that are attached to the wall of the channel. Since the glutamates are long and flexible, Nonner and Eisenberg et al. have suggested that these glutamates can be modeled by eight half-charged oxygen ions that represent the carboxylates at the end of each residue. These oxygen ions are confined to the filter but otherwise are mobile. We have used this model in simulations of the selectivity and conductance of this model calcium channel filter. Our studies confirm that this model behaves as a calcium filter; calcium ions will drive sodium ions from the filter. In many of our simulations, explicit water molecules are used with water molecules in both the filter and bath.