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

Science. 2014 Oct 17;346(6207):352-5. doi: 10.1126/science.1254840.

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bacterial Proteins / chemistry*
  • Bacterial Proteins / metabolism
  • Binding Sites
  • Crystallography, X-Ray
  • Molecular Dynamics Simulation
  • Potassium / metabolism*
  • Potassium Channels / chemistry*
  • Potassium Channels / metabolism
  • Protein Conformation
  • Static Electricity*
  • Water

Substances

  • Bacterial Proteins
  • Potassium Channels
  • prokaryotic potassium channel
  • Water
  • Potassium