High-level Expression of Silkworm Antimicrobial Peptide and Its Anti-infection to BmNPV

The peptide gene of Cecropin D was amplified by RT-PCR, cloned into the expression vector pET32a to generate the recombinant plasmid pET32a-CD. E.coli BL21 (DE3) were transformed by the plasmid and it was observed that the target gene was expressed at high-level in the form of fusion protein when induced with IPTG. The molecular weight of the fusion protein was 23kDa by SDS-PAGE and it constituted about 30% of total cell proteins, indicative of high levels of expression. The fusion Trx-CD was purified by Ni-NTA chromatography, and then cleaved into two parts, Trx (18kDa) and mature antimicrobial peptide CD(5kDa) by the enterokinase. The antim icrobial activity of the recombinant CD was checked by bacteria growth inhibition zone assay. Also, when BmNPV was mixed with CD for 4 h, the viral infectivity was markedly decreased. This indicated that the recombinant antimicrobial peptide CD has an inhibitory effect on BmNPV.