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Figure 1.
Fig. 1. Dependence of the conformation of the selectivity
filter of K^+ channels on K^+ concentration. (A) Close-up view
of the selectivity filter of wild-type KcsA channel in the
presence of high K^+ concentrations [K^+]. Two of the diagonally
opposite subunits are shown in stick representation. K^+ ions
are depicted as green spheres and water molecules as red
spheres. The K^+ binding sites in the selectivity filter are
labeled. (B) The structure of the selectivity filter in low
[K^+], represented as in (A). (C and D) Superposition of the
selectivity filter of wild-type KcsA in the presence of high
[K^+](blue) and low[K^+] (red). (C) shows a side view; (D)
depicts a top view extending  15 Å out from
the center of the filter. Aromatic residues that undergo
conformation changes are indicated.
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