Hornetin: the lethal protein of the hornet (Vespa flavitarsus) venom

By gel permeation on a Fractogel TSK HW 50 column followed by ion-exchange chromatography on carboxymethylcellulose CM 52, a lethal protein, designated hornetin, was purified from the venom of Vespa flavitarsus. Hornetin is a highly basic protein (pI 10.2) with a molecular mass of about 32 kDa. Its amino acid composition is characterized by a high content of lysine, aspartic and glutamic acid, and is devoid of tryptophan and cysteine. The lack of cysteine in the molecule is distinct from other known vespid venom proteins of comparable size. The i.v. LD50 of the toxin is 0.42 microgram per g mouse. Assayed on the red blood cells of the mouse and guinea-pig as well as isolated nerve muscle preparations of the chick and mouse, hornetin showed direct hemolytic activity and presynaptic neurotoxicity at microgram level and displayed musculotropic effect at higher concentrations.