Structural dynamics influences the antibacterial activity of a cell-penetrating peptide (KFF)3K

Given the widespread demand for novel antibacterial agents, we modified a cell-penetrating peptide (KFF)(3)K to transform it into an antibacterial peptide. Namely, we inserted a hydrocarbon staple into the (KFF)(3)K sequence to induce and stabilize its membrane-active secondary structure. The staples were introduced at two positions, (KFF)(3)K[5-9] and (KFF)(3)K[2-6], to retain the initial amphipathic character of the unstapled peptide. The stapled analogues are protease resistant contrary to (KFF)(3)K; 90% of the stapled (KFF)(3)K[5-9] peptide remained undigested after incubation in chymotrypsin solution. The stapled peptides showed antibacterial activity (with minimal inhibitory concentrations in the range of 2-16 mu M) against various Gram-positive and Gram-negative strains, contrary to unmodified (KFF)(3)K, which had no antibacterial effect against any strain at concentrations up to 32 mu M. Also, both stapled peptides adopted an a-helical structure in the buffer and micellar environment, contrary to a mostly undefined structure of the unstapled (KFF)(3)K in the buffer. We found that the antibacterial activity of (KFF)(3)K analogues is related to their disruptive effect on cell membranes and we showed that by stapling this cell-penetrating peptide, we can induce its antibacterial character.

Automated summary

This study modified a cell-penetrating peptide (KFF)(3)K by introducing a hydrocarbon staple into the sequence, transforming it into an antibacterial peptide. The stapled analogues showed antibacterial activity against various strains, in contrast to the unmodified peptide. Additionally, the stapled peptides exhibited improved protease resistance and a more defined secondary structure compared to the unstapled peptide.