Cooperative Transition between Open and Closed Conformations in Potassium Channels
Figure 3
Mean-square amino acid fluctuations in the KcsA channel.
The dips correspond to hinge regions. (A) Fluctuations in the first (solid) and second (dashed) slowest modes of motion of an isolated KcsA subunit. (B) Fluctuations in the first (solid black), second (dashed) and fifth (gray) slowest modes of motion of the subunit within the context of the homotetramer. (C) Structural elements and functionally important amino acids. The outer (M1), pore (PH), and inner (M2) helices are labeled in red, blue, and yellow bars, respectively, as in Figures 1 and 2. Elements and fragments of elements that are in the extracellular region of the cannel are presented using dashed bars; the bars of the inner and outer helices are dashed from the primary hinges identified in each ((A) and (B)). The approximate location of the selectivity filter is marked with “S”. The conserved Gly99 in the inner helix [2] is marked with a green triangle. Residues that are known to be functionally important based on single and double mutant experiments (Table S2 and Text S1) [8] are indicated with blank and solid red circles, respectively.