Beta toxin that binds site-4 of sodium channels (Nav), reduces peak current (observed on Nav1.6/SCN8A (IC(50)=172 nM), Nav1.1/SCN1A, Nav1.4/SCN4A (weak) and Nav1.5/SCN5A (weak)), shifts the voltage of activation toward more negative potentials (observed on Nav1.6 and Nav1.2 (weak)), and induces resurgent currents at negative voltages following brief and strong depolarizations (observed on Nav1.6, Nav1.1 (weak), Nav1.2 (weak), and Nav1.4 (weak)) (PubMed:22200496). Expressed by the venom gland. Has the structural arrangement of an alpha-helix connected to antiparallel beta-sheets by disulfide bonds (CS-alpha/beta). Does not show inhibition of peak current of Nav1.2, Nav1.3 and Nav1.7 (at 460 nM). Is neutralized by the single-chain antibody fragment 10FG2. Belongs to the long (4 C-C) scorpion toxin superfamily. Sodium channel inhibitor family. Beta subfamily.