Binds to voltage-gated sodium channels (Nav), and slows down the inactivation of mammalian Nav1.2/SCN2A, Nav1.3/SCN3A Nav1.4/SCN4A, Nav1.6/SCN8A, insect DmNav1 and BgNav1 channels, and arachnid VdNav1 channel (PubMed:22972919). This toxin acts by binding to site 3 of sodium channels. Has the CSbeta/beta fold, which comprises anti-parallel beta-sheets stabilized by three or four disulfide bonds. Has no effect on Nav1.5, Nav1.7 and Nav1.8 sodium channels and on Kv1.1, Kv1.2, Kv1.3, Kv1.4, Kv1.5, Kv1.6, Kv2.1, Kv3.1, Kv4.2, Kv4.3, Kv7.2, Kv7.4, Kv11.1/KCNH2/ERG1, and Shaker potassium channels. Belongs to the sea anemone type 3 (BDS) potassium channel toxin family.