Quantal charge redistributions accompanying the structural transitions of sodium channels

Abstract

Asymmetric displacement currents, I _g , 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 I _g properties were found to be similar to those of gating currents previously observed in native nerve preparations. I _g fluctuations were measured in order to ascertain the discreteness of the conformational changes which precede the channel opening. The autocorrelation of the fluctuations is consistent with a shot-like character of the elementary I _g 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.