Molecular Physiology and Biophysics Section, Porter Neuroscience Research Center, National Institutes of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892, USA.
J Gen Physiol. 2010 Dec;136(6):629-44. doi: 10.1085/jgp.201010517.
The four voltage sensors in voltage-gated potassium (Kv) channels activate upon membrane depolarization and open the pore. The location and motion of the voltage-sensing S4 helix during the early activation steps and the final opening transition are unresolved. We studied Zn(2+) bridges between two introduced His residues in Shaker Kv channels: one in the R1 position at the outer end of the S4 helix (R362H), and another in the S5 helix of the pore domain (A419H or F416H). Zn(2+) bridges readily form between R362H and A419H in open channels after the S4 helix has undergone its final motion. In contrast, a distinct bridge forms between R362H and F416H after early S4 activation, but before the final S4 motion. Both bridges form rapidly, providing constraints on the average position of S4 relative to the pore. These results demonstrate that the outer ends of S4 and S5 remain in close proximity during the final opening transition, with the S4 helix translating a significant distance normal to the membrane plane.
电压门控钾 (Kv) 通道中的四个电压传感器在膜去极化时激活并打开孔道。在早期激活步骤和最终开放转变期间，电压感应 S4 螺旋的位置和运动尚不清楚。我们研究了 Shaker Kv 通道中两个引入的 His 残基之间的 Zn(2+)桥：一个位于 S4 螺旋外端的 R1 位置（R362H），另一个位于孔域的 S5 螺旋（A419H 或 F416H）。在 S4 螺旋完成最后运动后，Zn(2+)桥在开放通道中很容易在 R362H 和 A419H 之间形成。相比之下，在早期 S4 激活后但在最后 S4 运动之前，R362H 和 F416H 之间会形成明显的桥。这两种桥都能迅速形成，这对 S4 相对于孔道的平均位置提供了约束。这些结果表明，在最终开放转变过程中，S4 和 S5 的外端保持接近，S4 螺旋沿垂直于膜平面的方向移动相当大的距离。
