Characterizing the Antibacterial Mechanism of Three Novel Histone-Derived Antimicrobial Peptides

Abstract

The rise in antibiotic resistant pathogens has sparked interest in antimicrobial peptides (AMPs), especially those that are active against a wide variety of bacterial strains. Cell penetrating AMPs are of particular importance for their potential as both drug delivery systems and antimicrobial agents. Buforin II (BF2) is a well-characterized antimicrobial peptide derived from histone subunit H2A that kills bacteria by translocating across cell membranes and binding to nucleic acids. In this study, we compared the mechanisms of action of three novel histone-derived antimicrobial peptides (HDAPs), termed DesHDAP1-3, to that of BF2. DesHDAP1's antibacterial potency is similar to that of BF2 across several bacterial species, while DesHDAP2 and DesHDAP3 are generally weaker antibacterial agents. Our current data also implies that DesHDAP1 shows increased cytotoxicity against cancerous cells lines compared to BF2. Lipid vesicle studies measuring the translocation of all three designed peptides showed that DesHDAP2 does not cross lipid membranes as readily as DesHDAP1, DesHDAP3, or BF2, which may explain its poor antibacterial activity. For comparison, we have also considered the membrane permeabilization caused by the designed peptides using a propidium iodide uptake assay. Finally, we have considered the role of nucleic acid binding in the mechanism of the designed peptides by measuring the DNA binding and antimicrobial activity of mutant versions of the designed peptides. This data shows that all three peptides may not show the same correlation between DNA binding and activity observed for BF2. An understanding of how the designed peptides function is an important step in assessing their therapeutic potential and considering future design strategies.