– 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. Beta-mammal toxin Css4 Protein, Centruroides suffusus, Recombinant (His & SUMO) is expressed in E. coli expression system with N-6xHis-SUMO tag. The predicted molecular weight is 23.6 kDa and the accession number is P60266.