Resting-State Structure and Gating Mechanism of a Voltage-Gated Sodium Channel

• Published in: Cell Vol. 178; no. 4; pp. 993 - 1003.e12
• Main Authors: Wisedchaisri, Goragot, Tonggu, Lige, McCord, Eedann, Gamal El-Din, Tamer M., Wang, Liguo, Zheng, Ning, Catterall, William A.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 08.08.2019
• Subjects: Action Potentials - physiology; Animals; Bacterial Outer Membrane - metabolism; Cell Line; cryo-EM; Cryoelectron Microscopy; Crystallography, X-Ray; disulfide crosslinking; electrophysiology; Escherichia coli - metabolism; gating charge; ion channel; Ion Channel Gating - physiology; membrane protein; Mutation; NaV; Protein Conformation, alpha-Helical; Sodium - metabolism; Spodoptera - cytology; voltage sensor; voltage-gated sodium channel; Voltage-Gated Sodium Channels - chemistry; Voltage-Gated Sodium Channels - metabolism; X-ray crystallography; X-ray crystallography; NaV; electrophysiology; voltage sensor; ion channel; disulfide crosslinking; membrane protein; gating charge; voltage-gated sodium channel; cryo-EM; Na(V)
• ISSN: 0092-8674; 1097-4172; 1097-4172
• DOI: 10.1016/j.cell.2019.06.031

Voltage-gated sodium (NaV) channels initiate action potentials in nerve, muscle, and other electrically excitable cells. The structural basis of voltage gating is uncertain because the resting state exists only at deeply negative membrane potentials. To stabilize the resting conformation, we inserted voltage-shifting mutations and introduced a disulfide crosslink in the VS of the ancestral bacterial sodium channel NaVAb. Here, we present a cryo-EM structure of the resting state and a complete voltage-dependent gating mechanism. The S4 segment of the VS is drawn intracellularly, with three gating charges passing through the transmembrane electric field. This movement forms an elbow connecting S4 to the S4-S5 linker, tightens the collar around the S6 activation gate, and prevents its opening. Our structure supports the classical “sliding helix” mechanism of voltage sensing and provides a complete gating mechanism for voltage sensor function, pore opening, and activation-gate closure based on high-resolution structures of a single sodium channel protein. [Display omitted] •Voltage shifting and disulfide locking capture a resting-state structure of NaVAb•Three gating charges translocate intracellularly through transmembrane electric field•Voltage sensor couples to pore opening by an elbow connecting S4 to the S4-S5 linker•Resting-state structure supports a sliding helix mechanism of gating An engineered bacterial NaV channel adopts a resting conformation in the absence of a membrane potential, enabling structural analysis and elucidation of the full voltage-dependent gating mechanism.