Figure 3.

Two-ion PMF for the wild-type Kv1.2 channel. The x and y axes indicate the distance along the pore axis of each ion; the ions are confined to lie within a cylinder of radius 8 Å oriented along the pore axis. The black arrow in the lower right quadrant of the plot indicates a minimum energy trajectory leading to conduction via the knock-on mechanism; initially ion 2 starts in the intracellular reservoir and ion 1 in the filter. Ion 2 approaches to about z = 0 Å before causing the second ion to begin to move out of the filter. Real conductions typically involve the movement of three or more ions, and the energy barrier in these cases could be relatively small.