Specific macromolecular transport systems, ion channels and pumps, provide the pathways to facilitate and control the passage of ions across the lipid membrane. Ion channels provide energetically favourable passage for ions to diffuse rapidly and passively according to their electrochemical potential. Selective ion channels are essential for the excitability of biological membranes: the action potential is a transient phenomenon that reflects the rapid opening and closing of voltage-dependent Na+-selective and K+-selective channels. One of the most critical functional aspects of K+ channels is their ability to remain highly selective for K+ over Na+ while allowing high-throughput ion conduction at a rate close to the diffusion limit. Permeation through the K+ channel selectivity filter is believed to proceed as a ‘knockon’ mechanism, in which 2–3 K+ ions interspersed by water molecules move in a single file. Permeation through the comparatively wider and less selective Na+ channels also proceeds via a loosely coupled knockon mechanism, although the ions do not need to be fully dehydrated. While simple structural concepts are often invoked to rationalize the mechanism of ion selectivity, a deeper analysis shows that subtle effects play an important role in these flexible dynamical structures.
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May 2017
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A His6 motif of the human calprotectin heterodimer with a bound Mn(II) ion. In this issue of Essays in Biochemistry, Neumann et al. look at the how pathogenic Neisseria species exploit host metaloproteins, such as calprotectin, to acquire essential transition metal ions. For further details, see pages 211-223. Image kindly provided by Elizabeth M. Nolan (Massachusetts Institute of Technology). - PDF Icon PDF LinkTable of Contents
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Review Article|
May 09 2017
Ion channels and ion selectivity
Benoît Roux
1Department of Biochemistry and Molecular Biology, University of Chicago, 929 E 57th Street, Chicago, IL 60637, U.S.A.
Correspondence: Benoît Roux (roux@uchicago.edu)
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Publisher: Portland Press Ltd
Received:
December 19 2016
Revision Received:
February 16 2017
Accepted:
March 01 2017
Online ISSN: 1744-1358
Print ISSN: 0071-1365
© 2017 The Author(s). Published by Portland Press Limited on behalf of the Biochemical Society
2017
Essays Biochem (2017) 61 (2): 201–209.
Article history
Received:
December 19 2016
Revision Received:
February 16 2017
Accepted:
March 01 2017
Citation
Stephen J. Lippard, Jeremy M. Berg, Benoît Roux; Ion channels and ion selectivity. Essays Biochem 9 May 2017; 61 (2): 201–209. doi: https://doi.org/10.1042/EBC20160074
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