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. Strongly affects skeletal muscle channels Nav1.4/SCN4A, poorly affects the neuronal channels Nav1.6/SCN8A and Nav1.2/SCN2A. Induces spastic paralysis of rear limbs, increased salivation, apnea, tachycardia and increased perspiration. 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 affect the cardiac Nav1.5/SCN5A, the peripheral nerve channel Nav1.7/SCN9A, and the voltage-dependent potassium channel Kv1.5/KCNA5. EC(50) is 3.5 uM. Belongs to the long (4 C-C) scorpion toxin superfamily. Sodium channel inhibitor family. Beta subfamily.