A generalized kinetic model describes ion-permeation mechanisms in various ion channels

Ion channels conduct various ions across biological membranes to maintain the membrane potential, to transmit the electrical signals, and to elicit the subsequent cellular responses by the signaling ions. Ion channels differ in their capabilities to select and conduct ions, which can be studied by the patch-clamp recording method that compares the current traces responding to the test voltage elicited at different conditions. In these experiments, the current-voltage curves are usually fitted by a sigmoidal function containing the Boltzmann factor. This equation is quite successful in fitting the experimental data in many cases, but it also fails in several others. Regretfully, some useful information may be lost in these data, which otherwise can reveal the ion-permeation mechanisms. Here we present a generalized kinetic model that captures the essential features of the current-voltage relations and describes the simple mechanism of the ion permeation through different ion channels. We demonstrate that this model is capable to fit various types of the patch-clamp data and explain their ion-permeation mechanisms.