Three-finger toxin that binds and inhibits the muscular nicotinic acetylcholine receptor (nAChR). The neuromuscular block is irreversible in chick biventer cervicis, but partially reversible in the rat diaphragm preparation. Expressed by the venom gland. LD(50) is 0.2 mg/kg by intraperitoneal injection in mice. Belongs to the snake three-finger toxin family. Ancestral subfamily. Orphan group II sub-subfamily.