SEMINAR @ SISSA, SBP, dr. C. Domene, Nov. 26 at 11 hrs.

[Barbara Corzani]

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STATISTICAL AND BIOLOGICAL PHYSICS SEMINAR
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Dott.
Carmen Domene
(Physical and Theoretical Chemistry Laboratory, Department of Chemistry, 
University of Oxford, Oxford, U.K)

Title:
"Atypical mechanism of conduction in K+ channels?"

Thu  Nov. 26, 2009 @ 11.00 a.m.

SISSA - Basement floor - room A
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Abstract:

Potassium channels can conduct K+ ions with rates of up 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 two main states, with two or three 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 2-3kcal mol-1. Here, we present an alternative mechanism for 
conduction of K+ in K+ 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+.
In view of the results, it would be interesting to revisit many of the 
kinetic models proposed in the literature that aimed at describing ion 
conduction in low- and high-conductance ion channels, some of which did not 
successfully achieve an agreement between experimental data for conductance 
and ion occupancies. Crystallographers are also likely to assume in their 
refinements that if a site is not occupied by an ion, the site is likely to 
be occupied by a water molecule, and this might not always be the case.