Cloning and expression of cathelicidins Bac5 gene of dairy cattle and antimicrobial activity of recombinant protein

A pair of primers were designed and synthesized based on the published Bac5 mRNA sequence of dairy cattle,then the 414 bp Bac5 gene without signal sequence was amplified by RT-PCR.The target gene was cloned into PET28a(+),and prokaryotic expression plasmid PET28a-Bac5 was constructed and transformed into E.coli Rosetta,Bac5 was expressed under the induction of IPTG.There was a clear protein band near the 19 ku identified by SDS-PAGE.The antimicrobial activity of expressed recombinant protein(rBac5) was identified by antimicrobial test,the result suggested that the recombinant protein had some antimicrobial activity to two standard strains and the three main strains separated from mastitis milk.