Single channel conductance measurements and high resolution structure and dynamics characterization from solid-state NMR will lead to structure-function and dynamics-function correlations for ion channels. Previous support through this grant has led to novel correlations for explaining the conductance specificity and efficiency in the monovalent cation selective channel, gramicidin A. Insights into cation binding, electrostatic reduction of potential energy barriers and Grotthus conductance has generated principles and predictions for other channels. Indeed, the realization that the selectivity filter region of the K+ channel from Streptomyces lividans is lined with backbone amide groups suggests that the gramicidin pore which is similarly lined is an important model system. Here we propose to study the KcsA channel from Streptomyces in collaboration with Chris Miller (Brandeis Univ.), who has overexpressed and reconstituted the channel in bilayers. We will also study the M2 protein from Influenza A virus, a H+ channel that has been overexpressed and reconstituted in our own lab thanks to a previous collaboration with Robert Lamb (Northwestern Univ.). And we will continue to search for fundamental explanations of conductance properties, such as channel flicker and open channel noise in the structure and dynamics of gramicidin A. The comparison of functional, dynamics and structural studies, all obtained from a lamellar phase lipid environment, is an important advantage for this approach. This work has broad implications in the field of ion channels through the elucidation of the molecular details for channel gating and blocking, and also in demonstrating a method for achieving high resolution structural and dynamic characterizations for membrane proteins in a lamellar phase lipid environment
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