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

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

Author information

1
Biomolecular Dynamics Group, Max Planck Institute for Biophysical Chemistry, 37077 Göttingen, Germany.
2
Department of Biochemistry, University of Oxford, Oxford OX1 3QU, UK. sc3210@gmail.com u.zachariae@dundee.ac.uk bgroot@gwdg.de.
3
Department of Structural Chemistry, University of Göttingen, 37077 Göttingen, Germany.
4
School of Engineering, Physics and Mathematics, University of Dundee, Dundee DD1 4HN, UK. College of Life Sciences, University of Dundee, Dundee DD1 5EH, UK. sc3210@gmail.com u.zachariae@dundee.ac.uk bgroot@gwdg.de.
5
Biomolecular Dynamics Group, Max Planck Institute for Biophysical Chemistry, 37077 Göttingen, Germany. sc3210@gmail.com u.zachariae@dundee.ac.uk bgroot@gwdg.de.

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.

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PMID:
25324389
DOI:
10.1126/science.1254840
[Indexed for MEDLINE]
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