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Atypical mechanism of conduction in potassium channels.

Journal
Proceedings of the National Academy of Sciences
Publisher
Proceedings of the National Academy of Sciences
Publication Date
Sep 22, 2009
Volume
106
Issue
38
Identifiers
DOI: 10.1073/pnas.0903226106
Keywords
Disciplines
  • Biology
License
Unknown

Abstract

Potassium channels can conduct passively K+ ions with rates of up to approximately 10(8) ions per second at physiological conditions, and they are selective to these species by a factor of 10(4) over Na+ ions. Ion conduction has been proposed to involve transitions between 2 main states, with 2 or 3 K+ ions occupying the selectivity filter separated by an intervening water molecule. The largest free energy barrier of such a process was reported to be of the order of 2-3 kcal mol(-1). Here, we present an alternative mechanism for conduction of K+ in potassium channels where site vacancies are involved, and we propose that coexistence of several ion permeation mechanisms is energetically possible. Conduction can be described as a more anarchic phenomenon than previously characterized by the concerted translocations of K+-water-K+.

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