Gating charge transfer due to fixed ionizable sites.

An alternative origin is suggested for one component of the gating charge transfer that is measured just prior to and during the opening of an ion channel. Rather than it originating solely from the motion of groups with fixed charge, some may stem from ionizable sites which remain fixed in position but change their state of charge. Such changes involve proton migration across the membrane. Two cases are discussed. In the first the ionizable group changes its charge in response to the change in its dielectric environment resulting from the formation of an aqueous pore and in the second the change is as the direct result of the applied trans-membrane voltage. Some of the predicted characteristics of this novel component of gating charge transfer are described.