Antimicrobial Activity and Action Mechanisms of Arg-Rich Short Analog Peptides Designed from the C-Terminal Loop Region of American Oyster Defensin (AOD)

Abstract

American oyster defensin (AOD) was previously purified from acidified gill extract of the American oyster, Crassostrea virginica. AOD is composed of 38 amino acids with three disulfide bonds and exhibits strong antimicrobial activity against Gram-positive bacteria as well as significant activity against Gram-negative bacteria. Here, to develop promising peptides into antibiotic candidates, we designed five arginine-rich analogs (A0, A1, A2, A3, and A4), predicted their loop and extended strand/random structures—including nine amino acids and a disulfide bond derived from the C-terminus of AOD—and described their antimicrobial and cytotoxic effects, as well as their modes of action. In our experimental results, the A3 and A4 analogs exhibited potent antimicrobial activity against all test organisms—including four Gram-positive bacteria, six Gram-negative bacteria, and Candida albicans—without cell toxicity. A sequence of experiments, including a membrane permeabilization assay, DNA binding study, and DNA polymerization inhibition test, indicated that the two analogs (A3 and A4) possibly did not act directly on the bacterial membrane but instead interacted with intracellular components such as DNA or DNA amplification reactions. AOD analogs also showed strong bacterial inhibition activity in the plasma environment. In addition, analog-treated microbial cells clearly exhibited membrane disruption, damage, and leakage of cytoplasmic contents. Collectively, our results suggest that two analogs, A3 and A4, have potent antimicrobial activity via DNA interaction and have the potential for development into novel antimicrobial agents.

Antimicrobial potential of a ponericin-like peptide isolated from Bombyx mori L. hemolymph in response to Pseudomonas aeruginosa infection

“…The result indicates that Bm-ponericin-L1 possibly affects intracellular metabolic reactions, causing induction in cytoplasmic damage or leakage (as highlighted). A similar finding was reported earlier for Gram-positive and Gram-negative bacteria treated with an defensin-like AMP derived from oyster 51 . In vitro antibiofilm activity of Bm-ponericin-L1 was measured at different concentrations against the biofilmforming bacteria P.aeruginosa and K.pneumoniae.…”

Membrane-Active Cyclic Amphiphilic Peptides: Broad-Spectrum Antibacterial Activity Alone and in Combination with Antibiotics

“…Furthermore, AMPs can kill pathogens by directing cytokines to the infection area, causing increased immunological responses . AMPs provide several advantages over traditional antibiotics, such as poor induction of resistance; broad-spectrum activity against a wide variety of bacteria, fungi, protozoans, viruses, and surprisingly even cancerous cells; lower toxicity to the host cells; being less harmful to both the environment and consumers; synergistic effects on the antimicrobial activity of antibiotics; and rapid killing or inhibiting of the pathogens. − …”

Arginine Homopeptide of 11 Residues as a Model of Cell-Penetrating Peptides in the Interaction with Bacterial Membranes

“…Regarding the antibacterial activity of Arg-rich peptides, it is known that their target is intracellular. One proposed mechanism is the binding of peptides to DNA, favored by the interaction of the guanidinium group of Arg with phosphate, blocking DNA polymerase and bacterial proliferation [34]. Its action on the second messenger c-di-GMP has also been suggested, preventing the formation of biofilm for P. aeruginosa [35].…”