Voltage-gated sodium (Na v ) channel Na v 1.7 has been targeted for the development of nonaddictive pain killers. Structures of Na v 1.7 in distinct functional states will offer an advanced mechanistic understanding and aid drug discovery. Here we report the cryoelectron microscopy analysis of a human Na v 1.7 variant that, with 11 rationally introduced point mutations, has a markedly right-shifted activation voltage curve with V 1/2 reaching 69 mV. The voltage-sensing domain in the first repeat (VSD I ) in a 2.7-Å resolution structure displays a completely down (deactivated) conformation. Compared to the structure of WT Na v 1.7, three gating charge (GC) residues in VSD I are transferred to the cytosolic side through a combination of helix unwinding and spiral sliding of S4 I and ∼20° domain rotation. A conserved WNФФD motif on the cytoplasmic end of S3 I stabilizes the down conformation of VSD I . One GC residue is transferred in VSD II mainly through helix sliding. Accompanying GC transfer in VSD I and VSD II , rearrangement and contraction of the intracellular gate is achieved through concerted movements of adjacent segments, including S4-5 I , S4-5 II , S5 II , and all S6 segments. Our studies provide important insight into the electromechanical coupling mechanism of the single-chain voltage-gated ion channels and afford molecular interpretations for a number of pain-associated mutations whose pathogenic mechanism cannot be revealed from previously reported Na v structures.

中文翻译：

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Na v 1.7 机电耦合过程中 S4 的展开和螺旋滑动以及 VSD 的域旋转

电压门控钠 (Nav) 通道钠v1.7 的目标是开发非成瘾性止痛药。Na的结构v1.7 处于不同的功能状态将提供先进的机械理解和帮助药物发现。在这里，我们报告了对人类 Na 的冷冻电子显微镜分析v1.7 变体，具有 11 个合理引入的点突变，具有显着右移的激活电压曲线与 V1/2达到 69 mV。第一次重复中的电压感应域 (VSD我) 在 2.7-Å 分辨率结构中显示完全向下（失活）的构象。与WT Na的结构相比v1.7、VSD中的三个门控电荷（GC）残基我通过 S4 的螺旋解旋和螺旋滑动的组合转移到胞质侧我和~20°域旋转。S3 细胞质末端的保守 WNФФD 基序我稳定 VSD 的向下构象我. 一个 GC 残基转移到 VSD 中二主要通过螺旋滑动。在 VSD 中伴随 GC 转移我和 VSD二, 细胞内门的重排和收缩是通过相邻节段的协调运动实现的, 包括 S4-5我, S4-5二, S5二, 以及所有 S6 段。我们的研究为单链电压门控离子通道的机电耦合机制提供了重要的见解，并为许多疼痛相关突变提供了分子解释，这些突变的致病机制无法从先前报道的 Nav结构。