Antibacterial activity affected by the conformational flexibility in glycine−lysine based α-helical antimicrobial peptides

Antimicrobial peptides often exhibit broad-spectrum activity due to a mechanism based on bacterial membrane disruption, which also reduces the development of permanent resistance —a desirable characteristic given the escalating multidrug resistance problem. Host cell toxicity, however, necessitates the design of artificial variants of natural AMPs to enhance selectivity and minimize side effects. Kiadins were designed using rules derived from natural peptides active against E. coli, along with a validated computational algorithm based on a training set of such peptides, followed by rational conformational adjustments. In vitro activity, tested against ESKAPE strains (including ATCC and clinical isolates), revealed a varied activity spectrum and cytotoxicity that only partially correlated with conformational flexibility. Peptides with a higher proportion of Gly were generally less potent. They caused less bacterial membrane alteration, as observed by flow cytometry and AFM, which correlates with structural characteristics as observed by circular dichroism spectroscopy and predicted by molecular dynamics calculations.