Direct Expression of Antimicrobial Peptides in an Intact Form by a Translationally Coupled Two-Cistron Expression System

We describe a novel prokaryotic expression system for the production of cationic antimicrobial peptides (AMPs). The method relies on a translationally coupled two-cistron system, in which the termination codon for the first cistron (which encodes the anionic polypeptide mIFc2, a derivative of human gamma interferon) overlaps with the initiation codon for the second cistron (which encodes a cationic AMP) in the sequence of 5'-TAATG-3'. By forming an insoluble complex with the AMP upon translation, the mIFc2 protein efficiently neutralized the toxicity of the coexpressed cationic AMP and minimized the sensitivity of AMP to proteolytic degradation in a host. The AMPs were retrieved from the insoluble inclusion bodies without any chemical or enzymatic cleavage step by simple cation-exchange chromatography. With our system, approximately 100 mg of various AMPs (buforin IIb, parasin I, and pexiganan) were obtained from 1 liter of Escherichia coli culture. Our expression system may represent a universal cost-effective solution for the mass production of intact AMPs in their natural forms.