Bacterial selectivity and plausible mode of antibacterial action of designed Pro‐rich short model antimicrobial peptides

Abstract

To develop novel Pro-rich model AMPs with shorter length and higher bacterial selectivity/therapeutic index (TI) than natural AMP, indolicidin, we synthesized a series of undodecapeptides derived from the sequence XXPXXPWXPXX-NH2 (X indicates Leu or Lys) with different ratios of Lys and Leu residues. Several Pro-rich model peptides (K7 WP3, K6 WL1 P3, K5 WL2 P3-1, K5 WL2 P3-2, and K4 WL3 P3) had approximate 8- to 11-fold higher bacterial selectivity/TI compared to indolicidin. These peptides selectively bind to negatively charged liposomes (EYPG/EYPG; 7:3, w/w) mimicking bacterial membranes. Their high selectivity to negatively charged phospholipids corresponds well with their high bacterial selectivity. Indolicidin showed almost complete depolarization of the cytoplasmic membrane of Staphylococcus aureus and dye-leakage from negatively charged liposomes at 10 microM, whereas all of Pro-rich model peptides had very little activity in these assays even at 80 microM, as observed in buforin 2. These results suggest that the ultimate target of our designed Pro-rich model peptides is probably the intracellular components (e.g. protein, DNA or RNA) rather than the cytoplasmic membranes. Collectively, our designed Pro-rich short model peptides appear to be excellent candidates for future development as a novel antimicrobial agent.

Ctenidins: antimicrobial glycine-rich peptides from the hemocytes of the spider Cupiennius salei

“…The targets of glycine-rich peptides in bacteria and fungi are not clear, but can be diverse. Besides the classical membrane disruption or its depolarization [38], ctenidins could inhibit intracellular components as mentioned for proline-rich peptides [39] or could hamper bacterial cell division as suggested for the glycine-and proline-rich coleoptericins [40]. Another glycine-rich peptide family, the attacins, exerts its activity against Gram-negative bacteria by inhibiting the synthesis of an outer membrane protein by interfering with the transcription of its genes [41].…”

Natural Antimicrobial Peptides from Eukaryotic Organisms

“…Some antimicrobial peptides like the pleurocidin and dermaseptin inhibit bacterial DNA synthesis while buforin II and tachyplesin bind to nucleic acid in general (Yonezawa et al, 1992). The proline rich AMP family target proteicious or nucleic acid intracellular molecules (Park et al, 2008), indeed members of the proline-rich AMP family like Drosocin, pyrrhocoricin, and apidaecin have been shown to act on bacterial GRO EL and Dna K proteins (Otvos et al, 2000).…”

Antimicrobial Action of the Cyclic Peptide Bactenecin on Burkholderia pseudomallei Correlates with Efficient Membrane Permeabilization

“…CA-MA has potent antimicrobial activities against Escherichia coli and Bacillus subtilis , without hemolytic activity [24]. Analogs of CA-MA also exhibited strong antimicrobial activities due to the cationic and amphipathic structure [25], [26].…”