Voltage-gated ion channels sense transmembrane voltage changes via a paddle-shaped motif that includes the C-terminal part of the third transmembrane segment (S3b) and the N-terminal part of the fourth segment (~(NT)S4) that harbors voltage-sensing arginines. Here, we find that residue triplets in S3b and ~(NT)S4 can be deleted individually, or even in some combinations, without compromising the channels' basic voltage-gating capability. Thus, a high degree of complementarity between these S3b and ~(NT)S4 regions is not required for basic voltage gating per se. Remarkably, the voltage-gated Shaker K~+ channel remains voltage gated after a 43 residue paddle sequence is replaced by a glycine triplet. Therefore, the paddle motif comprises a minimal core that suffices to confer voltage gating in the physiological voltage range, and a larger, modulatory part. Our study also shows that the hydrophobic residues between the voltage-sensing arginines help set the sensor's characteristic chemical equilibrium between activated and deactivated states.
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机译：电压门控离子通道通过桨状基序感应跨膜电压变化，该桨状基序包括第三跨膜段（S3b）的C端部分和带有电压的第四段（〜（NT）S4）的N端部分精氨酸。在这里，我们发现S3b和〜（NT）S4中的残留三元组可以单独删除，甚至可以以某些组合删除，而不会损害通道的基本电压门控功能。因此，基本电压门控本身并不需要这些S3b和〜（NT）S4区域之间的高度互补性。值得注意的是，在用甘氨酸三联体替代了43个残基桨叶序列后，电压门控的Shaker K +通道仍保持电压门控。因此，桨叶图案包括足以在生理电压范围内提供电压门控的最小核心，以及较大的调制部分。我们的研究还表明，电压感测精氨酸之间的疏水残基有助于设定传感器在活化态和非活化态之间的化学平衡特征。
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