Spider venom neurotoxin that blocks voltage-gated sodium channel Nav1.3/SCN3A in human (IC(50)=80 nM) and rat (IC(50)=160 nM). Partially inhibits human Kv11.1/KCNH2/ERG (25% at 175 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 10 (Hwtx-1) family. 11 (haplotoxin-2) subfamily.