Binds voltage-independently at site-3 of sodium channels (Nav) and inhibits the inactivation of the activated channels, thereby blocking neuronal transmission. Expressed by the venom gland. Has the structural arrangement of an alpha-helix connected to antiparallel beta-sheets by disulfide bonds (CS-alpha/beta). Only three disulfide bridges can be formed, because only seven cysteines are present. Belongs to the long (3 C-C) scorpion toxin superfamily.