Abstract:[Objective] In order to study the antimicrobial activity of Gal-7 mature peptide in vitro, we constructed an engineered E. coli strain contains chicken beta-defensin-7 (gal-7) gene encoding Gal-7 mature peptide published previously. [Methods] Based on the gene sequence, we synthesized the gal-7 gene, cloned into pGEX-6p-1 prokaryotic expression vector and subsequently transformed into the E. coli BL21(DE3). The E. coli strain contains the expression vector was induced with IPTG and the fusion protein GST-Gal7 was purified by affinity chromatograph, then Prescission protease was used to remove GST-label to form Gal-7 mature peptide. The molecular weight of purified Gal-7 mature peptide was monitored by MALDI-TOF-MS and antimicrobial activity was tested by the agar well diffusion assay. Besides 2-fold dilution method was used to determine the minimum inhibitory concentration of Gal-7 mature peptide. [Results] We successfully constructed the engineered E. coli strain expressing pGEX-6p-Gal7 and GST-label was cleaved by Prescission protease. The molecule weight of purified Gal-7 mature peptide was 5 516 D, it exhibited antimicrobial activity against Micrococcus flavus (NCIB 8166), S. aureus (ATCC 25923), E. faecalis (ATCC 29212), E. coli (CMCC 44102) with MICs 16.875, 67.5, 67.5, 135 mg/L respectively. [Conclusion] The GST-Gal7 protein was successfully expressed in E. coli, besides the Gal-7 mature peptide without GST-label showed antimicrobial activity against several indicator strains.
