Expression and characterization of cecropinXJ, a bioactive antimicrobial peptide from Bombyx mori (Bombycidae, Lepidoptera) in Escherichia coli

Insect antimicrobial peptides (AMPs) have a broad antimicrobial spectrum. To aid the characterization of the gene function and further applications, we cloned the gene of cecropinXJ into the prokaryotic expression vector pET32a and expressed cecropinXJ in Escherichia coli BL2l (DE3). Following induction by isopropyl-β-D-thiogalactoside (IPTG), a 25 kDa fusion peptide of cecropinXJ with a tagged thioredoxin (Trx) protein was highly expressed in E. coli. The yield was 10 mg/l culture medium following purification on nickel-nitrilotriacetic acid (Ni-NTA) metal affinity chromatography matrices. The purified recombinant antibacterial peptide, cecropinXJ, retained a high stability against Staphylococcus aureus over a temperature range from 4 to 100°C and a pH range from pH 2.0 to 12.0. The minimum inhibitory concentration (MIC) of the fusion protein against S. aureus was 0.4 μM. The recombinant cecropinXJ is also cytotoxic to several types of human cancer cells.