| Preferential binding of K+ ions in the selectivity filter at equilibrium explains high selectivity of K+ channels. | |
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MedLine Citation:
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PMID: 23148260 Owner: NLM Status: Publisher |
Abstract/OtherAbstract:
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K(+) channels exhibit strong selectivity for K(+) ions over Na(+) ions based on electrophysiology experiments that measure ions competing for passage through the channel. During this conduction process, multiple ions interact within the region of the channel called the selectivity filter. Ion selectivity may arise from an equilibrium preference for K(+) ions within the selectivity filter or from a kinetic mechanism whereby Na(+) ions are precluded from entering the selectivity filter. Here, we measure the equilibrium affinity and selectivity of K(+) and Na(+) ions binding to two different K(+) channels, KcsA and MthK, using isothermal titration calorimetry. Both channels exhibit a large preference for K(+) over Na(+) ions at equilibrium, in line with electrophysiology recordings of reversal potentials and Ba(2+) block experiments used to measure the selectivity of the external-most ion-binding sites. These results suggest that the high selectivity observed during ion conduction can originate from a strong equilibrium preference for K(+) ions in the selectivity filter, and that K(+) selectivity is an intrinsic property of the filter. We hypothesize that the equilibrium preference for K(+) ions originates in part through the optimal spacing between sites to accommodate multiple K(+) ions within the selectivity filter. |
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Authors:
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Shian Liu; Xuelin Bian; Steve W Lockless |
Publication Detail:
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Type: JOURNAL ARTICLE Date: 2012-11-12 |
Journal Detail:
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Title: The Journal of general physiology Volume: - ISSN: 1540-7748 ISO Abbreviation: J. Gen. Physiol. Publication Date: 2012 Nov |
Date Detail:
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Created Date: 2012-11-13 Completed Date: - Revised Date: - |
Medline Journal Info:
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Nlm Unique ID: 2985110R Medline TA: J Gen Physiol Country: - |
Other Details:
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Languages: ENG Pagination: - Citation Subset: - |
Affiliation:
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Department of Biology, Texas A&M University, College Station, TX 77843. |
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From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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