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Atypical mechanism of conduction in potassium channels

Author:
Furini, Simone, Domene, Carmen
Source:
Proceedings of the National Academy of Sciences of the United States of America 2009 v.106 no.38 pp. 16074-16077
ISSN:
0027-8424
Subject:
energy, ions, potassium, potassium channels, sodium
Abstract:
Potassium channels can conduct passively K⁺ ions with rates of up to [almost equal to]10⁸ ions per second at physiological conditions, and they are selective to these species by a factor of 10⁴ 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⁺.
Agid:
2366111