Ruta Vanessa, Chen Jiayun, MacKinnon Roderick
Howard Hughes Medical Institute, Laboratory of Molecular Neurobiology and Biophysics, New York 10021, USA.
Cell. 2005 Nov 4;123(3):463-75. doi: 10.1016/j.cell.2005.08.041.
Voltage-dependent ion channels open and conduct ions in response to changes in cell-membrane voltage. The voltage sensitivity of these channels arises from the motion of charged arginine residues located on the S4 helices of the channel's voltage sensors. In KvAP, a prokaryotic voltage-dependent K+ channel, the S4 helix forms part of a helical hairpin structure, the voltage-sensor paddle. We have measured the membrane depth of residues throughout the KvAP channel using avidin accessibility to different-length tethered biotin reagents. From these measurements, we have calibrated the tether lengths and derived the thickness of the membrane that forms a barrier to avidin penetration, allowing us to determine the magnitude of displacement of the voltage-sensor paddles during channel gating. Here we show that the voltage-sensor paddles are highly mobile compared to other regions of the channel and transfer the gating-charge arginines 15-20 A through the membrane to open the pore.
电压依赖性离子通道会响应细胞膜电压的变化而打开并传导离子。这些通道的电压敏感性源于位于通道电压传感器S4螺旋上的带电荷精氨酸残基的运动。在原核生物电压依赖性钾通道KvAP中，S4螺旋形成了一种螺旋发夹结构的一部分，即电压传感器桨叶。我们利用抗生物素蛋白对不同长度的连接生物素试剂的可及性，测量了整个KvAP通道中残基的膜深度。通过这些测量，我们校准了连接长度，并推导出形成抗生物素蛋白渗透屏障的膜的厚度，这使我们能够确定通道门控期间电压传感器桨叶的位移幅度。在这里我们表明，与通道的其他区域相比，电压传感器桨叶具有高度的流动性，并通过膜传递门控电荷精氨酸15 - 20埃以打开孔道。
