cDNA sequence analysis and expression of kappa-bungarotoxin from Taiwan banded krait.

The cDNAs encoding kappa-bungarotoxin was constructed from the cellular RNA isolated from the venom glands of Bungarus multicinctus by reverse transcription-polymerase chain reaction. A high degree of nucleotide sequence homology was observed between kappa-bungarotoxin and other kappa-neurotoxins. The kappa-bungarotoxin was subcloned into the expression vector pET32a(+) and transformed into BL21(DE3) E. coli strain. The recombinant toxin was expressed as a fusion protein. Recombinant kappa-bungarotoxin was separated from the fused protein by cleavage with CNBr and purified by reversed phase high performance liquid chromatography. In addition to kappa-bungarotoxin, the cDNA fragment encoding kappa3-bungarotoxin was also found in the cDNA mixtures prepared from the cellular RNA of the venom glands of the same snake. This result suggests that the venom glands of Taiwanese B. multicinctus should secrete at least two kinds of kappa-neurotoxins.