Blocks voltage-gated sodium channels (Nav). Causes immediate spastic paralysis and death in mice within 1 min of injection at dose levels of 1.5 ug per mouse. Expressed by the venom gland. The presence of a 'disulfide through disulfide knot' structurally defines this protein as a knottin. Belongs to the neurotoxin 03 (Tx2) family. 04 subfamily.