Armstrong C M, Bezanilla F
J Gen Physiol. 1977 Nov;70(5):567-90. doi: 10.1085/jgp.70.5.567.
Gating current (Ig) has been studied in relation to inactivation of Na channels. No component of Ig has the time course of inactivation; apparently little or no charge movement is associated with this step. Inactivation nonetheless affects Ig by immobilizing about two-thirds of gating charge. Immobilization can be followed by measuring ON charge movement during a pulse and comparing it to OFF charge after the pulse. The OFF:ON ratio is near 1 for a pulse so short that no inactivation occurs, and the ratio drops to about one-third with a time course that parallels inactivation. Other correlations between inactivation and immobilization are that: (a) they have the same voltage dependence; (b) charge movement recovers with the time coures of recovery from inactivation. We interpret this to mean that the immobilized charge returns slowly to "off" position with the time course of recovery from inactivation, and that the small current generated is lost in base-line noise. At -150 mV recover is very rapid, and the immobilized charge forms a distinct slow component of current as it returns to off position. After destruction of inactivation by pronase, there is no immobilization of charge. A model is presented in which inactivation gains its voltage dependence by coupling to the activation gate.
门控电流（Ig）已被研究与钠通道失活的关系。Ig的任何成分都没有失活的时间进程；显然，这一步骤几乎没有电荷移动或没有电荷移动。然而，失活通过固定约三分之二的门控电荷来影响Ig。固定化可以通过测量脉冲期间的开启电荷移动并将其与脉冲后的关闭电荷进行比较来跟踪。对于短到不会发生失活的脉冲，关闭：开启比率接近1，并且该比率随着与失活平行的时间进程下降到约三分之一。失活与固定化之间的其他相关性在于：（a）它们具有相同的电压依赖性；（b）电荷移动随着从失活恢复的时间进程而恢复。我们将此解释为意味着固定化电荷随着从失活恢复的时间进程缓慢回到“关闭”位置，并且产生的小电流在基线噪声中丢失。在-150 mV时恢复非常迅速，并且固定化电荷在回到关闭位置时形成明显的缓慢电流成分。在胰蛋白酶破坏失活后，没有电荷的固定化。提出了一个模型，其中失活通过与激活门耦合而获得其电压依赖性。
