RESUMEN
The vip3A gene of Bt9816C was cloned and the sequencing result was submitted to GenBank (accession no.AY945939). The gene was identified as a novel vip3Aa gene, which was assigned name vip3Aa18 by the Bacillus thuringiensis delta-endotoxin nomenclature committee. Subsequently, vip3Aa18 was expressed in Escherichia coli BL21 and bioassay demonstrated that the purified recombinant Vip3Aa18 had high toxicity against Helicoverpa armigera and Spodoptera exigua. The results of sequence analysis revealed that a carbohydrate binding domain exists on the C-termini 536 to 667 residues of Vip3Aa18,which maybe participate in binding to midgut receptors in susceptible insects. Moreover, a transmembrane helices located on N-termini 272 to 292 residues was proposed responding for pore formation. Furthermore, a putative disulfide bond was found in the Vip3Aa18 sequence. The specific structures and sites of Vip3Aa18 sequence imply potential function.