Perozo E, MacKinnon R, Bezanilla F, Stefani E
Jules Stein Eye Institute, Los Angeles, California 90024.
Neuron. 1993 Aug;11(2):353-8. doi: 10.1016/0896-6273(93)90190-3.
In voltage-dependent ion channels, a voltage sensor region is responsible for channel activation and an aqueous pore is responsible for ion conduction. These two processes have been traditionally considered to be independent. We describe here a mutation in the putative pore region (W434F) that completely abolishes ion conduction without affecting the gating charge of the channel. Gating currents in the nonconductive mutant were found to be identical in their kinetic and steady-state properties to those in conductive channels. Gating current measurements could be performed without subtracting pulses and in the presence of normal physiological solutions. Application of internal tetraethylammonium (an open channel blocker) induced Off charge immobilization for large depolarizations, suggesting that the internal tetraethylammonium-binding site becomes available upon depolarization. We concluded that for this mutant, although the conduction pathway is not functional, the channel can still undergo the closed-open conformation in response to voltage changes.
在电压依赖性离子通道中，电压感受器区域负责通道激活，而水性孔道负责离子传导。传统上认为这两个过程是相互独立的。我们在此描述了一个假定孔道区域的突变（W434F），该突变完全消除了离子传导，却不影响通道的门控电荷。发现非传导性突变体中的门控电流在动力学和稳态特性方面与传导性通道中的门控电流相同。无需减去脉冲且在正常生理溶液存在的情况下即可进行门控电流测量。施加内部四乙铵（一种开放通道阻滞剂）会导致大去极化时的关闭电荷固定，这表明内部四乙铵结合位点在去极化时变得可用。我们得出结论，对于这个突变体，尽管传导途径不起作用，但通道仍可响应电压变化经历关闭 - 开放构象。
