Antimicrobial peptides with high proteolytic resistance for combating gram-negative bacteria.

Poor proteolytic resistance is an urgent problem to be solved in the clinical application of AMPs, yet common solutions, such as complicated chemical modifications and utilization of D-amino acids, greatly increase the difficulty and cost of producing AMPs. In this work, a set of novel peptides was synthesized base on an anti-trypsin/chymotrypsin hydrolytic peptide structure unit (XYPX)n (X represents I, L and V; Y represents R and K), which was designed using a systematic natural amino acid arrangement. Of these peptides, 16 with 7 repeat units had the highest average selectivity index (GMSI=99.07) for all of the gram-negative bacteria tested, and maintained highly effective in combating E. coli infection in vivo. Importantly, 16 also had dramatic resistance against a high concentration of trypsin/chymotrypsin hydrolysis and exerted bactericidal activity through a membrane-disruptive mechanism. Overall, these findings provide new approaches for the development of anti-protease hydrolytic peptides that target gram-negative bacteria.