Inhibits both peak current and fast inactivation of voltage-gated sodium channels (Nav) channels. Inhibits the inactivation of Nav on DRG neurons (EC(50)=1.77 uM) and peak current of cardiac myocytes (IC(50)=0.90 uM). Expressed by the venom gland. The presence of a 'disulfide through disulfide knot' structurally defines this protein as a knottin. Monoisotopic mass. Belongs to the neurotoxin 10 (Hwtx-1) family. 37 (Jztx-31) subfamily.