Antimicrobial activities and mechanisms of truncated and amino-acid-substituted peptides derived from bacteriocin PZJ5

Truncation and amino acid residue substitution are common methods to optimise the design of antimicrobial peptides (AMPs). In the present work, seven truncated and residue-substituted derivatives of Plantaricin ZJ5 (PZJ5) were designed and synthesised. PZJ5-5 was a truncation that simultaneously contained three substituted amino-acid residues, with enhanced antimicrobial activity and low haemolytic activity. The effects of PZJ5-5 on Escherichia coli microstructure were investigated using scanning and transmission electron microscopy, which indicated that its antibacterial mechanism was similar to PZJ5. C-terminal amidation of PZJ5-5 (PZJ5-7) was deleterious, and resulted in a dramatic reduction in potency against E. coli and Listeria monocytogenes, with no potency against the other three indicator bacteria. Truncation and residue substitution of bacteriocin PZJ5 changed its antimicrobial activities and specificities, which provided a rationale for bacteriocin design.