Potassium channel KcsA

Burykin, A. Kato, M. Warshel, A., Exploring the origin of the ion selectivity of the KcsA potassium channel, Proteins 2003, 52, 412-426. 

Finally, it is worth keeping in mind that the protein may be perturbed reversibly by the conditions of the NMR experiment. For example, a recent study demonstrated that removal of the bulk buffer that typically separates from the sample during magic angle spinning reversibly altered the conformation of the selectivity filter of the KcsA potassium channel addition of buffer to the rotor restored the conformation.101 Based on this observation of a hydration-induced shift in conformation, it seems prudent to maintain high hydration levels for NMR studies of proteins in general. 

Gross, A., Columbus, L., Hideg, K., Altenbach, C., and Hubbell, W. L. (1999). Structure of the KcsA potassium channel from Streptomyces lividans a site-directed spin labeling study of the second transmembrane segment. Biochemistry 38, 10324-10335. 

Chill JH, Louis JM, Miller C, Bax A. NMR study of the tetrameric KcsA potassium channel in detergent micelles. Protein Sci. 2006 15 684-689. 

Chill JH, Louis JM, Baber JL, Bax A. Measurement of 15N relaxation in the detergent-solubilized tetrameric KcsA potassium channel. J. Biomol. NMR 2006 36 123-136. 

Bucher D, Guidoni L, Rothlisberger U (2007) The protonation state of the Glu-71/Asp-80 residues in the KcsA potassium channel a first-principles QM/MM molecular dynamics study. Biophys J 93(7) 2315... 

The C-terminal domain comprises the transmembrane region including the ion-conducting pore (3). Althou ftie exact number of transmembrane helices remains to be established, a model based on homology with die bacterial KcsA potassium channel structure has been established to define key structural elements important for ion conductance, ion selectivity, and the gating mechanism (4). 

The selectivity of ion channels is often determined by only a handful of amino acids. Thus, the amino acids Glu-Glu-Glu-Glu (EEEE) determine the selectivity of the calcium channel of the heart [9] the amino acids Asp-Glu-Lys-Ala (DEKA) determine the selectivity of the sodium channel of nerve and muscle cells [10]. The structure of ion channels is notoriously difficult to determine because channel proteins do not easily crystal-hze. They are normally found in hpid membranes, and so methods suitable for crystallizing soluble proteins are not too helpful. Several structures have been determined, most notably, the KcsA potassium channel [4]. 

Bucher D et al (2010) Coordination numbers of K" and Na" ions inside the selectivity filter of the KcsA potassium channel insights from first principles molecular dynamics. Biophys J 98 L47-L49... 

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