Depressant insect beta-toxins cause a transient contraction paralysis followed by a slow flaccid paralysis. They 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). This toxin is active only on insects and causes a transient contraction paralysis followed by a slow flaccid paralysis. Expressed by the venom gland. Has the structural arrangement of an alpha-helix connected to antiparallel beta-sheets by disulfide bonds (CS-alpha/beta). LD(50) is 67 ng/100 mg of body weight of blowfly larvae (S.falculata) and 138 ng/100 mg of body weight of cockroaches (B.germanica). Belongs to the long (4 C-C) scorpion toxin superfamily. Sodium channel inhibitor family. Beta subfamily.