The voltage dependence of different voltage-gated potassium channels, described by the voltage at which half of the channels are open (V), varies over a range of 80 mV and is influenced by factors such as the number of positive gating charges and the identity of the hydrophobic amino acids in the channel’s voltage sensor (S4). Here we explore by experimental manipulations and molecular dynamics simulation the contributions of two derived features of an electric fish potassium channel (Kv1.7a) that is among the most voltage-sensitive family potassium channels known. These are a patch of four contiguous negatively charged glutamates in the S3-S4 extracellular loop and a glutamate in the S3b helix. We find that these negative charges affect V by separate, complementary mechanisms. In the closed state, the S3-S4 linker negative patch reduces the membrane surface charge biasing the channel to enter the open state while, upon opening, the negative amino acid in the S3b helix faces the second (R2) gating charge of the voltage sensor electrostatically biasing the channel to remain in the open state. This work highlights two evolutionary novelties that illustrate the potential influence of negatively charged amino acids in extracellular loops and adjacent helices to voltage dependence.

中文翻译：

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双重机制有助于增强电鱼钾通道的电压依赖性

不同电压门控钾通道的电压依赖性，用一半通道打开时的电压 (V) 来描述，在 80 mV 的范围内变化，并受到正门控电荷数量和身份等因素的影响通道电压传感器 (S4) 中的疏水性氨基酸。在这里，我们通过实验操作和分子动力学模拟探索电鱼钾通道 (Kv1.7a) 的两个派生特征的贡献，电鱼钾通道是已知对电压最敏感的钾通道家族之一。这些是 S3-S4 细胞外环中的四个连续带负电荷的谷氨酸和 S3b 螺旋中的谷氨酸的补丁。我们发现这些负电荷通过单独的互补机制影响 V。在关闭状态下，S3-S4 连接子负片会减少膜表面电荷，使通道偏置进入打开状态，而在打开时，S3b 螺旋中的负氨基酸面向电压传感器的第二个 (R2) 门控电荷静电偏置通道以保持打开状态。这项工作突出了两个进化新颖性，说明了细胞外环和相邻螺旋中带负电的氨基酸对电压依赖性的潜在影响。