Potent and selective inhibitor of Nav1.7/SCN9A sodium channels. Inhibits Nav1.7/SCN9A peak current (IC(50)=13 nM) (PubMed:31647222). In vivo, does not induce visible signs of toxicity when intravenously injected into mice (PubMed:31647222). Expressed by the venom gland. The presence of a 'disulfide through disulfide knot' structurally defines this protein as a knottin. When conjugated with a fluorophore, could be used as a tracer in surgery to discriminate nerves from their surrounding tissues, particularly during tumor resections or after traumatic injuries. The dye is conjugated to Lys-4 residue and this synthetic peptide shows only a small decrease in ability to inhibit Nav1.7/SCN9A compared to native peptide. Belongs to the neurotoxin 30 (phrixotoxin) family.