Purification and Chemical Studies of a Toxin from the Venom of Lapemis hardwickii (Hardwick's Sea Snake)

The toxin was isolated from the venom of sea snake, Lapemis hardwickii (Hardwick's sea snake), through a four-step purification by column chromatography. The toxin was proven homogenous by zonal electrophoresis, analytical ultra-centrifugation, and isoelectric focusing. The toxin was also isolated in crystal form. The lethality of the purified toxin increased 23-fold when compared to the original venom. The molecular weight as determined by amino acid composition and by sedimentation equilibrium was approximately 6800. The toxin consists of 61 amino acid residues and does not contain a free sulfhydryl group. End group analysis indicated that there is a histidine at the NH2-terminal and an aspartic acid or asparagine at the COOH-terminal. The isoelectric point as determined by isoelectric focusing was 9.85. When the tryptophan residue in the purified toxin was modified with 2-nitrophenylsulfenyl chloride, 2-hydroxy-5-nitrobenzylbromide, or N-bromosuccinimide, the toxicity was completely lost.