Potassium channels can conduct passively K+ ions with rates of up to ≈108 ions per second at physiological conditions, and they are selective to these species by a factor of 104 over Na+ ions. Ion conduction has been proposed to involve transitions between 2 main states, with 2 or 3 K+ ions occupying the selectivity filter separated by an intervening water molecule. The largest free energy barrier of such a process was reported to be of the order of 2–3 kcal mol−1. Here, we present an alternative mechanism for conduction of K+ in potassium channels where site vacancies are involved, and we propose that coexistence of several ion permeation mechanisms is energetically possible. Conduction can be described as a more anarchic phenomenon than previously characterized by the concerted translocations of K+–water–K+.
|Journal||Proceedings of the National Academy of Sciences of the United States of America|
|Publication status||Published - 1 Sept 2009|
- Bacterial Proteins, Binding Sites, Computer Simulation, Crystallography, X-Ray, Ion Channel Gating, Models, Molecular, Potassium, Potassium Channels, Protein Conformation, Protein Structure, Tertiary, Thermodynamics, Water