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. This toxin is active only on mammals. 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 0.12 ug/kg in mouse by intracerebroventricular injection and LD(50) is 115 ug/kg in mouse by subcutaneous injection. LD(100) is 3 ug/kg by intracranial injection into mice. Belongs to the long (4 C-C) scorpion toxin superfamily. Sodium channel inhibitor family. Beta subfamily. Authors of PubMed:21329715 cite the nucleotide sequence HQ262493 as coding for Css8 (AC P0DL83), but the sequence corresponds to Css4. For this reason, the corresponding cross-reference is indicated in this entry.