Characterization and cloning of long neurotoxin homolog from Naja naja atra

The cDNA encoding a long neurotoxin homolog was constructed from the cellul ar RNA isolated fom the venom glands of Naja naja atra (Taiwan cobra) by re verse transcription-polymerase chain reaction. BLAST searches for sequence similarity in the GeneBank databases reveal that the cDNA sequence of the l ong neurotoxin homolog is not highly homologous with long and short neuroto xins. Although the long neurotoxin homolog exhibited an activity to inhibit acetylcholine-induced muscle contractions as Naja naja atra cobrotoxin, th e degree of inhibition caused by the addition of long neurotoxin homolog wa s only approximately 35% of that observed with the addition of cobrotoxin. Moreover, the primary structure of the long neurotoxin homolog did not fulf ill the characteristic features of long or short neurotoxins. Together with long neurotoxin homologs from other snake species, they probably represent an evolutionary divergence between long and short neurotoxins.