Quantal charge redistributions accompanying the structural transitions of sodium channels

Asymmetric displacement currents, Ig, associated with the gating of nerve sodium channels have been recorded in cell-attached macropatches of Xenopus laevis oocytes injected with exogenous mRNA coding for rat-brain-II sodium channels. The Ig properties were found to be similar to those of gating currents previously observed in native nerve preparations. Ig fluctuations were measured in order to ascertain the discreteness of the conformational changes which precede the channel opening. The auto-correlation of the fluctuations is consistent with a shot-like character of the elementary Ig contributions. The variance of the fluctuations indicates that most of the gating-charge movement that accompanies the activation of a single sodium channel occurs in 2 to 3 brief packets, each carrying an equivalent of about 2.3 electron charges.