Binds voltage-dependently at site 3 of sodium channels (Nav) and inhibits the inactivation of the activated channels, thereby blocking neuronal transmission. Has effect on SCN4A/SCN1B, and SCN5A/SCN1B, has no effect on SCN2A/SCN1B, and SCN10A/SCN1B. Possesses the highest efficacy for the insect sodium channel para/tipE. Also interacts with sodium channels in cardiac cells. Shows lethality to crabs (PubMed:22015268). LD(50) is 21 ug/kg by intracerebroventricular injection into mice. Belongs to the sea anemone sodium channel inhibitory toxin family. Type I subfamily.