Cooperative Transition between Open and Closed Conformations in Potassium Channels
Figure 1
Dynamic fluctuations in the KcsA channel.
The K-channel may fluctuate between the open and closed conformations. The upper panels show a side view of the X-ray crystal structure of the channel (B; PDB identifier 1bl8) and the slowest mode of fluctuations in opposite directions (A and C). The lower panels show an intracellular view of the corresponding conformations: the X-ray structure (E) and the fluctuations (D and F). The outer (M1), inner (M2), and pore helices (PH) are displayed in red, yellow and blue, respectively. The Gly99 hinge is shown in green. To open the pore, i.e., to switch from the conformation in “C” and “F” to “A” and “D,” the inner and outer helices bend around their hinge sites, the inner helices rotate in a clockwise direction and swing away from the permeation pathway. The arrows indicate the rotations of the inner helices in each subunit. The picture was prepared using Pymol (http://www.pymol.org) [64].