Brownian dynamics simulation of pH-effects on conductance through potassium channels.

A new theory termed "tunnel-acid-group-potential" (TAGPT), explaining the effect of pHo and pH(i) on ion conductance through different membrane channels, is presented. It is suggested that shifts in pHo and pH(i) lead to changes in values of negative charges generated by acid groups of side chains of some polar (Glu-, Asp-) amino acid residues, lining the tunnel part of the channel. The resulting modification of electrostatic field influences the heights of rate-limiting energy barriers (for ion transport) in the transition zones between the tunnel and the vestibules, followed by changes in channel conductivity.