Crystallization and Properties of Cobrotoxin from Formosan Cobra Venom.

Crotoxin, the first crystalline protein from snake venom isolated by Slotta and Fraenkel-Conrat (1) in 1938 from the venom of Crotalus terr$cus terr$icus, carried both neurotoxic and hemolytic activities. However, it was found later that there were at least two markedly different proteins in this crystalline preparation (2). In 1944, De (3) isolated crystalline hemolysin from the venom of Naja naja (Indian cobra). Fourteen years later, crystalline lecithinase A, which was confirmed to correspond to the hemolysin, was isolated from the venom of Naja naja atra (Formosan cobra) by Suzuki, Iwanaga, and Kawachi (4). All three crystalline preparations described above had phospholipase A activity. However, in a series of studies by Yang et al. (5-7) and others (8-14) on snake venom, the venom toxicity was distinguished from enzyme activities and it was proved that the enzymes contained in the venom are not the main cause of lethal toxicity. It was reported in the preceding paper (15) that two toxic proteins devoid of enzyme activities have been highly purified from Formosan cobra venom by means of ammonium sulfate fractionation and repeated chromatography on a carboxymethyl cellulose column. One of them is very toxic, 6.7 times more toxic than the original venom, and has an LDsO to mice of 905 per mg. Attempts were made to crystallize the more toxic protein for further studies, and fine, rod-shaped crystals were finally obtamed. This crystalline protein, we designated as “cobrotoxin.” The present report deals with the methods of purification, crystallization, and some properties of cobrotoxin from cobra venom.