Purification and Functional Analysis of Recombinant Nisin Resistance Protein (NSR) Expressed in Escherichia coli
大肠杆菌重组乳链菌肽抗性蛋白(NSR)的表达纯化及其功能分析

Nisin is a cationic antimicrobial peptide produced by some lactic acid bacteria. However, expression of nisin resistance protein (NSR) could confer nisin resistance on some non-nisin-producing Lactococ-cus lactis. To deeply elucidate molecular mechanism underlying NSR-mediated nisin resistance, an NSR mutant with N-terminal 38 amino acid residues deleted (NSRA38) was overexpressed in Escherichia coli by fusion with GST. Purified NSRA38 was obtained through glutathione (GSH) affinity chromatography followed by cleavage of GST tag. Putative proteolytic activity of NSRA38 was determined in vitro against nisin. Antimicrobial activity analysis revealed that nisin lost its bactericidal activity after incubation with NSRA38. Further reversed-phase high performance liquid chromatography (RP-HPLC) analysis indicated that NSRA38 displayed proteolytic activity against nisin, thus inactivating the antimicrobial peptide. The current study paves the way for in-depth functional studies on NSR.