Toxic proteins of snakes and scorpions

Abstract

A chromatographic method utilising Sephadex C-25 as an ion exchanger and molecular sieve permits both small and large scale separation of the constituents of snake venom. Cross-contamination of peak materials is diminished when Triton X-100 is incorporated in eluting buffers. Two long neurotoxins and two cardiotoxins isolated fromNaja naja (cobra) venom differ from other such toxins, isolated earlier, in their amino acid composition. Inorganic pyrophosphatase activity is found in snake venoms, and the more basic of the two cardiotoxins (cardiotoxin II) of cobra venom possesses intrinsic enzyme activity. The properties of the latter toxin as an enzyme have been studied. Enzyme activity does not seem essential for the protein to display cardiotoxicity. Cardiotoxin II, as isolated, contains four magnesium atoms per mole, which do not appear to be essential for its function. At least two atoms of magnesium per mole are required for the pyrophosphatase action. The venom of two Indian scorpions (Buthus tamulus andHeterometrus bengalensis) are amenable to fractionation by chromatography on Sephadex C-25. Two fractions fromButhus tamulus elicit an initial hypotensive effect and then a hypertensive effect in rats. The former is cholinergic and the latter adrenergic in nature. Both fractions induce a biphasic contracture of the indirectly stimulated rat diaphragm. Of the two venoms, that ofButhus tamulus is more toxic to mice.