Beta toxins bind voltage-independently at site-4 of sodium channels (Nav) and shift the voltage of activation toward more negative potentials thereby affecting sodium channel activation and promoting spontaneous and repetitive firing (By similarity). Inhibits sodium channels Nav1.4/SCN4A, Nav1.5/SCN5A and Nav1.6/SCN8A (PubMed:27871874). Also has a weak inhibitory effect on Nav1.2/SCN2A (PubMed:27871874). Is lethal to mice (PubMed:27871874). Expressed by the venom gland. Has the structural arrangement of an alpha-helix connected to antiparallel beta-sheets by disulfide bonds (CS-alpha/beta). Is lethal to mice by intraperitoneal injection of 0.5 ug (and higher doses). Has no inhibitory effect on Nav1.1/SCN1A, Nav1.3/SCN3A and Nav1.7/SCN9A. Is not neutralized by the two single-chain antibody fragments LR and 10FG2. Belongs to the long (4 C-C) scorpion toxin superfamily. Sodium channel inhibitor family. Beta subfamily.