Researching on the Selectivity Permeability Mechanism of K Channels Based on a Hierarchical Model

Potassium channels are membrane proteins that allow the passage of potassium ions at near diffusion rates while severely limiting the flux of the slightly smaller sodium ions. Based on the three dimensional structure of KcsA with a D- alanine at position 77 (KcsA^D-Ala77), the authors use a hierarchical model of K channel selectivity permeability process involving ab initio quantum calculations and Brownian dynamics. The results showed that the mutated K channel, KcsA^D-Ala77, lost its ability of discriminating the sodium ions from the potassium ions which is consistent with the experimental data. Our results indicate that interactions between permeant ions and the selectivity filter can influence ion selectivity.