Lethal neurotoxin active on both vertebrates and insects. Slows the inactivation of vertebrate tetrodotoxin-sensitive voltage-gated sodium channels (Nav) and most likely insect sodium channels presumably by binding to site 3 of the channel. Effects are an increase in resting tension, a muscle fasciculation and a decrease in indirect twitch tension. It fails to affect tetrodotoxin-resistant sodium currents. Expressed by the venom gland. The presence of a 'disulfide through disulfide knot' structurally defines this protein as a knottin. In this species, the venom of the male is lethal rather than that of the female. Is the sole lethal toxin in the venom of male M.bradleyi. Belongs to the neurotoxin 06 (delta-actx) family.