Rational design, antimicrobial mechanisms of non-perfectly amphipathic peptides with α-helical propensity

Antimicrobial peptides (AMPs) are natural substances, gaining attention for prevention of drug-resistant characteristics. To optimize the antibacterial efficacy and cellular selectivity of the AMPs, the antimicrobial peptide with the sequence LKKISQYYQKFA was designated as L-0, extracted from sheep α_s2-casein, which was used as a template to design five peptides through the mirror symmetry and amino acid substitution. Among these designed peptides, W-4, which featured an imperfect amphipathic α-helical structure, exhibited the strongest antimicrobial activity, comparable to cefixime. In addition, both the cellular selectivity and condition stability of W-4 were improved, compared with the template peptide. Molecular docking was further performed to show that W-4 preferentially targeted bacterial membrane mimics than L-0, thus exerting strong antimicrobial activity with minimal damage to eukaryotic membranes. W-4 exerted stronger bactericidal activity than the template peptide, due to its greater capacity to permeabilize and disrupt the cell membrane. Therefore, imperfect amphipathic peptides have strong antibacterial activities and are promising candidates for traditional antibiotics in food and pharmaceutical industries.