Antibacterial effect of Trp, Val, and Arg-rich peptides

Abstract

As the excessive antibiotic misuse has caused drastic emergence of resistance and superbacteria, discovery of novel antibiotics is urgent. The cationic antimicrobial peptides (CAMPs) have been investigated as alternative antibiotics with broad antibacterial spectrum and novel mode of action. However, because of the low stability by proteolytic degradation and inactivation in high salt condition, there are limitations to evaluate CAMPs as therapeutic agents. Therefore, in this report, I tried to overcome those drawnbacks with construction of peptide library by applying two chemical modifications and analyzing the activity of CAMPs in amino acid composition aspect keeping with their strengths. For increasing stability and activity in physiological condition, peptides were synthesized by using D-form amino acids and C-terminus was amidated. Tryptophan, arginine, and valine were utilized in short-length peptide library design for the hydrophobicity, cationicity, and amphipathicity which are crucial features of CAMPs. Among designed 10 peptides, the final candidates, called LS 9 and LS 10, showed potent activity with broad specturm and low cytoxicity, so their killing kinetics and membrane interaction mechanism were further investigated. Both peptides not only exhibited high activity in high salt condition, but also completely inactivated against Gram-negative and Gram-positive by exhibiting rapid killing kinetics with permeation of outer membrane and depolarization of bacterial membrane without induction of resistance. Additionally, LS 9 and LS 10 showed different manner of action in all aspects. This study would be useful to study for mode of action and construction of antimicrobial peptides, especially for correlation of amino acid and antibacterial activity of CAMPs.