Document Type
Journal Article
Date of this Version
1-17-2014
Publication Source
PLoS ONE
Volume
9
Issue
1
Start Page
e86079
DOI
10.1371/journal.pone.0086079
Abstract
The ability of biological ion channels to conduct selected ions across cell membranes is critical for the survival of both animal and bacterial cells. Numerous investigations of ion selectivity have been conducted over more than 50 years, yet the mechanisms whereby the channels select certain ions and reject others are not well understood. Here we report a new application of Jarzynski’s Equality to investigate the mechanism of ion selectivity using non-equilibrium molecular dynamics simulations of Na+ and K+ ions moving through the KcsA channel. The simulations show that the selectivity filter of KcsA adapts and responds to the presence of the ions with structural rearrangements that are different for Na+ and K+. These structural rearrangements facilitate entry of K+ ions into the selectivity filter and permeation through the channel, and rejection of Na+ ions. A mechanistic model of ion selectivity by this channel based on the results of the simulations relates the structural rearrangement of the selectivity filter to the differential dehydration of ions and multiple-ion occupancy and describes a mechanism to efficiently select and conduct K+. Estimates of the K+/Na+ selectivity ratio and steady state ion conductance for KcsA from the simulations are in good quantitative agreement with experimental measurements. This model also accurately describes experimental observations of channel block by cytoplasmic Na+ ions, the “punch through” relief of channel block by cytoplasmic positive voltages, and is consistent with the knock-on mechanism of ion permeation.
Copyright/Permission Statement
This article is under a Creative Commons Attribution 4.0 license. This license permits any user to download, print out, copy, archive, and distribute the article, so long as appropriate credit is given to the authors and source of the work.
Recommended Citation
Ngo, V., Stefanovski, D., Haas, S., & Farley, R. A. (2014). Non-Equilibrium Dynamics Contribute to Ion Selectivity in the KcsA Channel. PLoS ONE, 9 (1), e86079-. http://dx.doi.org/10.1371/journal.pone.0086079
Included in
Cellular and Molecular Physiology Commons, Veterinary Pathology and Pathobiology Commons
Date Posted: 22 December 2016
This document has been peer reviewed.
Comments
At the time of publication, author Darko Stefanovski was affiliated with University of Southern California. Currently, he is a faculty member at the School of Veterinary Medicine at the University of Pennsylvania.