cDNA sequence analysis of a novel neurotoxin homolog from Taiwan banded krait.

The cDNA encoding a novel protein was constructed from the cellular RNA isolated from the venom glands of Bungarus multicinctus (Taiwan banded krait) by reverse transcription-polymerase chain reaction. The deduced amino acid sequence of this novel protein contains 68 amino acid residues with 10 cysteine residues. Comparative sequence analyses show that it is structurally related to alpha-bungarotoxin and kappa-bungarotoxins from Bungarus multicinctus venom. Eight out of the ten cysteine residues in this protein are located at the homologous positions as those in the neurotoxins. However, instead of the fifth disulfide linkage appearing in loop II of alpha-bungarotoxin and kappa-bungarotoxins, the other two cysteine residues in this novel toxin are situated at the N-terminal region. Phylogenetic analyses suggest that it probably represents a small evolutionary divergence between the long and short neurotoxins.