Open-state structure of veratridine-activated human Na<sub>v</sub>1.7 reveals the molecular choreography of fast inactivation

Almost all the reported cryo-EM structures of eukaryotic voltage-gated sodium (Nav) channels, including those of human Nav1.1-Nav1.8, represent various inactivated states that are characteristic of a non-conductive pore domain (PD) surrounded by voltage-sensing domains (VSDs) in varying up conformations. To capture an open-state Navstructure, we treated purified human Nav1.7 with a natural neurotoxin veratridine (VTD) and solved its cryo-EM structures. Two VTD-bound Nav1.7 complexes were obtained. One, with VTD inserted in the IFM-binding corner (site I), resembles other inactivated structures. The other, wherein VTD traverses the central cavity (site C), represents an activated conformation with the constriction diameter of 8.2 Å at the intracellular gate. Structural analysis reveals the mechanism of action of VTD’s bimodal modulation of Nav channels. More importantly, structural comparison between the open and inactivated states provides advanced molecular insight into the fast inactivation process.