Recombinant expression of a novel antimicrobial peptide consisting of human α-defensin 5 and Mytilus coruscus mytilin-1 in Escherichia coli

Abstract

Antibiotic peptides are a battery of broad-spectrum antibacterial cationic polypeptides widely distributed in the plant and animal kingdoms. Among them, the human defensins are the first line of defense against pathogens and Mytilin, which is isolated from mussel serum, plays a key role in the mussel defense system. The antibacterial activity of these two peptides is generally ascribed to their overall positive charge, which enables them to disrupt bacterial membrane integrity and function. The aim of this study was to develop an effective method for the biosynthesis of a fusion peptide containing human α-defensin 5 (HD5) and Mytilin-1 in Escherichia coli to improve the antimicrobial activity. The individual HD5 and Mytilin-1 peptides were also synthesized for comparison with the fusion peptide. All the peptides, expressed as soluble fusions with the peptide thioredoxin, were isolated using a three-step purification strategy involving nickel-Sepharose chromatography, enterokinase cleavage, and cationic exchange chromatography. The identity of the peptides was confirmed by SDS-PAGE. Antimicrobial activity assays demonstrated that all the recombinant peptides had strong bactericidal properties and that the HD5 and Mytilin-1 fusion protein displayed higher activity against E. coli and Staphylococcus aureus. The results of this study provide a platform for the development of novel cationic peptides for biological studies.