Reversible inhibitor of neuronal sodium channels (Nav1.2/ SCN2A) that binds in proximity to site 1 and displays increasing affinity as the membrane potential is depolarized. Induces excitatory symptoms and spastic paralysis in mice. Expressed by the venom gland. The presence of a 'disulfide through disulfide knot' structurally defines this protein as a knottin. Contains 7 disulfide bonds. LD(50) is 0.05 mg/kg by intracerebroventricular injection into mice. Belongs to the neurotoxin 04 (omega-agtx) family. 02 (Tx1) subfamily.