Permeation study of the potassium channel from streptomyces Lividans

A three-state hopping model is established ac-cording to experiments to study permeation of an open-state potassium channel from Streptomyces Lividans (KcsA po-tassium channel). The master equations are used to charac-terize the dynamics of the system. In this model, ion conduc-tion involves transitions of three states, with one three-ion state and two two-ion states in the selectivity filter respec-tively. In equilibrium, the well-known Nernst equation is deduced. It is further shown that the current follows Micha-elis-Menten kinetics in steady state. According to the pa-rameters provided by Nelson, the current-voltage relation-ship is proved to be ohmic and the current-concentration relationship is also obtained reasonably. Additional valida-tion of the model in the characteristic time to reach the steady state for the potassium channel is also discussed. This model lays a possible physical basis for the permeation of ion channel, and opens an avenue for further research.