Spider venom neurotoxin that blocks voltage-gated sodium channel Nav1.3/SCN3A in human (IC(50)=1 uM) and rat (IC(50)=1 uM). Partially inhibits human Kv11.1/KCNH2/ERG (40% at 10 uM). Expressed by the venom gland. The presence of a 'disulfide through disulfide knot' structurally defines this protein as a knottin. Has no effect on human and rat Nav1.8/SCN10A (Ref.1). Belongs to the neurotoxin 30 (phrixotoxin) family.