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  • Title: Conduction in a biological sodium selective channel.
    Author: Stock L, Delemotte L, Carnevale V, Treptow W, Klein ML.
    Journal: J Phys Chem B; 2013 Apr 11; 117(14):3782-9. PubMed ID: 23452067.
    Abstract:
    The crystal structure of NavAb, a bacterial voltage gated Na(+) channel, exhibits a selectivity filter (SF) wider than that of K(+) channels. This new structure provides the opportunity to explore the mechanism of conduction and help rationalize its selectivity for sodium. Recent molecular dynamics (MD) simulations of single- and two-ion permeation processes have revealed that a partially hydrated Na(+) permeates the channel by exploring three SF binding sites while being loosely coupled to other ions and/or water molecules; a finding that differs significantly from the behavior of K(+) selective channels. Herein, we present results derived from a combination of metadynamics and voltage-biased MD simulations that throws more light on the nature of the Na(+) conduction mechanism. Conduction under 0 mV bias explores several distinct pathways involving the binding of two ions to three possible SF sites. While these pathways are very similar to those observed in the presence of a negative potential (inward conduction), a completely different mechanism operates for outward conduction at positive potentials.
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