Referenced in: none

Automatically associated channels: Slo1

Title: Ion permeation in K⁺ channels occurs by direct Coulomb knock-on.

Authors: David A Köpfer, Chen Song, Tim Gruene, George M Sheldrick, Ulrich Zachariae, Bert L de Groot

Journal, date & volume: Science, 2014 Oct 17 , 346, 352-5

PubMed link: http://www.ncbi.nlm.nih.gov/pubmed/25324389

Abstract
Potassium channels selectively conduct K(+) ions across cellular membranes with extraordinary efficiency. Their selectivity filter exhibits four binding sites with approximately equal electron density in crystal structures with high K(+) concentrations, previously thought to reflect a superposition of alternating ion- and water-occupied states. Consequently, cotranslocation of ions with water has become a widely accepted ion conduction mechanism for potassium channels. By analyzing more than 1300 permeation events from molecular dynamics simulations at physiological voltages, we observed instead that permeation occurs via ion-ion contacts between neighboring K(+) ions. Coulomb repulsion between adjacent ions is found to be the key to high-efficiency K(+) conduction. Crystallographic data are consistent with directly neighboring K(+) ions in the selectivity filter, and our model offers an intuitive explanation for the high throughput rates of K(+) channels.