Effect of Intracellular Diffusion on Current–Voltage Curves in Potassium Channels

We study the effect of intracellular ion diffusion on ionic currents permeating through the cell membrane. Ion flux across the cell membrane is mediated by specific channels, which have been widely studied in recent years with remarkable results: very precise measurements of the true current across a single channel are now available. Nevertheless, a complete understanding of this phenomenon is still lacking, though molecular dynamics and kinetic models have provided partial insights. In this paper we demonstrate, by analyzing the KcsA current-voltage currents via a suitable lattice model, that intracellular diffusion plays a crucial role in the permeation phenomenon. We believe that the interplay between the channel behavior and the ion diffusion in the cell is a key ingredient for a full explanation of the current-voltage curves.