Neurotoxins of Bungarus multicinctus vernom. Purification and partial characterization.

The purification to homogeneity of nine neurotoxic components of the venom of Bungarus multicinctus is described. The purified components include alpha-bungarotoxin and two other alpha-type synaptic toxins and beta-bungarotoxin and five other beta-type synaptic toxins. The purified toxins have been characterized by electrophoresis, isoelectric focusing, amino acid analysis, and N-terminal amino acid determination. The alpha-type synaptic neurotoxins constitute a discrete class with molecular weights of 7000-8500, isoelectric points (pI) of 9.0-9.2, and N-terminal isoleucine or methionine. The beta-type synaptic neurotoxins constitute a second group with molecular weights of 20 000-22 000 and pI = 8.8-9.7. Fractions 10 through 13 exhibit a chain structure consisting of a 6000-7000 light chain and a 11 000-15 000 heavy chain apparently covalently stabilized by interchain disulfides. Fractions 9A and 14 were single chains of 11 000-14 000 which resemble the sequenced beta-type synaptic neurotoxin notexin (Halpert, J., and Eaker, D. (1975), J. Biol. Chem. 250, 6990). All of the beta-type synaptic toxins have a single tryptophan and N-terminal aspartic acid or asparagine.