Binds at site 4 of sodium channels (Nav) and inhibits the fast inactivation of cockroach channels. This toxin is active only on insects. Has a potent activity against S.litura larvae. Expressed by the venom gland. The presence of a 'disulfide through disulfide knot' structurally defines this protein as a knottin. Could be considered as a biological insecticide candidate, when fused to Galanthus nivalis agglutinin (GNA), a protein with the potential to cross the insect gut. This chimeric Pl1a/GNA variant shows a gain in toxicity against insects when administered orally, while maintaining similar effects as the wild-type toxin when injected. Transport of Pl1a/GNA variant from gut contents to the hemolymph of cabbage moth larvae, and binding to the nerve chord, has been shown. This variant has been found to be orally toxic against cabbage moth (Mamestra brassicae), housefly (Musca domestica), and the hemipteran Acyrthosiphon pisum. Belongs to the neurotoxin 07 (Beta/delta-agtx) family. 02 (aga-3) subfamily.