NDLI: On the selective ion binding hypothesis for potassium channels

Content Provider	PubMed Central
Author	Kim, Ilsoo Allen, Toby W.
Abstract	The mechanism by which K+ channels select for K+ over Na+ ions has been debated for the better part of a century. The prevailing view is that K+ channels contain highly conserved sites that selectively bind K+ over Na+ ions through optimal coordination. We demonstrate that a series of alternating sites within the KcsA channel selectivity filter exists, which are thermodynamically selective for either K+ (cage made from two planes of oxygen atoms) or Na+ ions (a single plane of four oxygen atoms). By combining Bennett free energy perturbation calculations with umbrella sampling, we show that when K+ and Na+ are both permitted to move into their preferred positions, the thermodynamic preference for K+ over Na+ is significantly reduced throughout the entire selectivity filter. We offer a rationale for experimental measures of thermodynamic preference for K+ over Na+ from Ba2+ blocking data, by demonstrating that the presence of Ba2+ ions exaggerates K+ over Na+ thermodynamic stability due to the different binding locations of these ions. These studies reveal that K+ channel selectivity may not be associated with the thermodynamics of ions in crystallographic K+ binding sites, but requires consideration of the kinetic barriers associated with the different multi-ion permeation mechanisms.
Related Links	http://dx.doi.org/10.1073/pnas.1110735108
Ending Page	17968
Page Count	6
Starting Page	17963
File Format	PDF
ISSN	00278424
e-ISSN	10916490
Journal	Proceedings of the National Academy of Sciences of the United States of America
Issue Number	44
Volume Number	108
Language	English
Publisher	National Academy of Sciences
Publisher Date	2011-11-01
Access Restriction	Open
Rights Holder	National Academy of Sciences
Subject Keyword	General Research in Higher Education
Content Type	Text
Resource Type	Article
Subject	Multidisciplinary

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