Enhanced Synergism and Mechanism of Action Studies of Synthetic Antimicrobial Metallopeptides

Abstract

Antimicrobial peptides (AMPs) are found throughout most kingdoms of life, are an important part of host immunity, and have been shown to act synergistically in various organisms to ameliorate bacterial infections. Herein, we report the synergistic behavior observed between two AMPs, Sub5 and CP10A, against E. coli. In addition, enhanced synergistic activity against E. coli and MRSA 43300 for two derivatives of Sub5, extended with the amino‐terminal copper and nickel (ATCUN) binding motif, is observed when dosed together with CP10A, while displaying little cytotoxicity towards human dermal fibroblasts. All three combinations of peptides co‐localized within bacterial cells as evidenced by fluorescence confocal microscopy. Investigations into the mechanism of synergy shows that all peptides indirectly damage DNA within cells, while only the ATCUN derivatives can oxidize phospholipids. Combinations of peptides were also shown to upregulate the concentration of reactive oxygen species within both E. coli and MRSA 43300. These results suggest that the production of reactive oxygen species is an important aspect mechanistically and further highlights the potential of these metallopeptides to aid in the treatment of antibiotic‐resistant infections.

Activity and Synergy of Cu-ATCUN Antimicrobial Peptides

“…Comparison of MIC values among the OV3 derivatives shows that the addition of the YG hook at the C-terminal end of the peptide drastically improved the activity of the parental OV3-00 peptide as compared to the OV3 parental peptide in Escherichia coli 25922 (Table 2). As in previous work conducted in our laboratory, the addition of the GGH motif did not seem to enhance the antimicrobial activity of the peptide but does not abrogate the activity either [7,8,11]. Of interest is the observation that no peptide across the tested strains retained improved activity over the others.…”

“…We further examine peptide derivatives that have been further modified by the addition of an amino terminal copper/nickel-binding (ATCUN) motif, which has been shown to offer distinct modes of activity to known antimicrobial peptides [7,9]. The antimicrobial and antiviral activities of ATCUN-modified peptides are now extensively documented [7,[9][10][11][12][13]. Before proceeding to the results of the investigations, a brief introduction to the cathelicidin and clawed-toe frog derivative peptides used in these studies is provided.…”

Tackling antimicrobial stewardship through synergy and antimicrobial peptides

“…[77][78][79] The domain has been utilized in our lab to confer alternative activity on antimicrobial peptides that did not naturally contain an ATCUN motif. [80][81][82][83] Zinc-binding peptides have also shown important antimicrobial activity. For example, thanatin, a zinc binding peptide, was shown to have clinical activity against the highly problematic and resistant New Delhi metallo-β-lactamase-1 (NDM-1) by stripping the lactamase of its required zinc cofactor.…”

“…77–79 The domain has been utilized in our lab to confer alternative activity on antimicrobial peptides that did not naturally contain an ATCUN motif. 80–83…”

“…While the mechanisms are not fully elucidated, the ATCUN motif has been shown to confer enhanced synergistic activity with natural and synthetic peptides beyond that shown by their non-ATCUN containing counterpart. 83 The enhanced formation of reactive oxygen species (ROS), conferment of lipid oxidation, and alternative mechanisms of action may contribute to this activity.…”