Conformational Transitions of Ionic Channels

Abstract

Ion transport through a channel may be described as a series of thermally activated processes in which the ion moves from a binding site over an energy barrier to an adjacent site. The “binding sites” are the minima in the potential-energy profile that result from interactions of the ion with ligand groups of the channel. In the traditional treatment of ionic channels, the energy levels of wells and barriers are considered to be fixed, i.e., independent of time and not influenced by the movement of the ion. This description, which corresponds to an essentially static picture of protein structure, represents a useful approximation in certain cases. Recent findings on the dynamics of proteins, however, suggest a more general concept of barrier structure.