Voltage-sensor activation with a tarantula toxin as cargo
Voltage-sensor activation with a tarantula toxin as cargo
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DOI：
10.1038/nature03873
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发表时间：
2005-08-11
期刊：
影响因子：
64.8
通讯作者：
Swartz, KJ
中科院分区：
文献类型：
--
作者：
Phillips, LR;Milescu, M;Swartz, KJ
电压激活的Na+、Ca~(2+)和K~+(Kv)通道的开放和关闭是整个生物电信号和化学信号传递的基础，但电压敏感的结构基础尚不清楚。汉密尔顿毒素是一种狼蛛毒素，它通过与电压传感器桨(1-5)结合来抑制Kv通道，电压传感器桨(1-5)是由S3b和S4螺旋(6)组成的电压敏感结构域中的关键螺旋-转弯-螺旋基序。毒素的活性表面是两亲性的(7，8)，相关毒素已被证明分配到膜(9-12)中，这增加了毒素集中在膜上并仅与电压传感器微弱而短暂地相互作用的可能性。在这里，我们研究了毒素-通道相互作用的动力学和状态依赖性，以及毒素在膜中的物理位置。我们发现，汉密尔顿毒素与电压传感器形成了一个强大而稳定的复合体，在负电压下的静止(闭合)构象和正电压下的激活(开放)构象之间的波动远远超过电压传感器之间的波动。电压传感器的激活降低了毒素的亲和力，这解释了为什么毒素稳定了静止的构象。我们还发现，当韩毒素进入膜中时，它被定位在一个界面区，Trp 30位于距离双层中心约8.5埃的位置。这些结果表明，电压传感器桨被毒素作为货物激活，并表明在激活过程中，桨不会超过双层的外半部分。
The opening and closing of voltage-activated Na+, Ca2+ and K+ (Kv) channels underlies electrical and chemical signalling throughout biology, yet the structural basis of voltage sensing is unknown. Hanatoxin is a tarantula toxin that inhibits Kv channels by binding to voltage-sensor paddles(1-5), crucial helix-turn-helix motifs within the voltage-sensing domains that are composed of S3b and S4 helices(6). The active surface of the toxin is amphipathic(7,8), and related toxins have been shown to partition into membranes(9-12), raising the possibility that the toxin is concentrated in the membrane and interacts only weakly and transiently with the voltage sensors. Here we examine the kinetics and state dependence of the toxin - channel interaction and the physical location of the toxin in the membrane. We find that hanatoxin forms a strong and stable complex with the voltage sensors, far outlasting fluctuations of the voltage sensors between resting ( closed) conformations at negative voltages and activated ( open) conformations at positive voltages. Toxin affinity is reduced by voltage-sensor activation, explaining why the toxin stabilizes the resting conformation. We also find that when hanatoxin partitions into membranes it is localized to an interfacial region, with Trp 30 positioned about 8.5 angstrom from the centre of the bilayer. These results demonstrate that voltage-sensor paddles activate with a toxin as cargo, and suggest that the paddles traverse no more than the outer half of the bilayer during activation.