1.A.1.14.5
Voltage-gated Na⁺ channel, Na_vCh or Na_vAb. The 3d-structure is known (3ROW; Payandeh et al., 2011; 4MW3A-D; 4+ selectivity through partial dehydration of Na⁺ via its direct interaction with conserved glutamate side chains). The pore is preferentially occupied by two ions, which can switch between different configurations by crossing low free-energy barriers (Furini and Domene, 2012). Jiang et al. 2018 presented high-resolution structures of NavAb with the analogous gating-charge mutations that have similar functional effects as in the human channels that cause hypokalaemic and normokalaemic periodic paralysis.  Wisedchaisri et al. 2019 presented a cryo-EM structure of the resting state and a complete voltage-dependent gating mechanism via the voltage sensor (VS). 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. This 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 (Wisedchaisri et al. 2019). (see also TC#s 1.A.1.10.4 and 1.A.1.11.32). The transport reaction catalyzed by Na_vCh is: Na⁺ (in) ⇌ Na⁺ (out)