Understanding interactions of Citropin 1.1 analogues with model membranes and their influence on biological activity

Abstract

The rapid emergence of resistant bacterial strains has made the search for new antibacterial agents an endeavor of paramount importance. Cationic antimicrobial peptides (AMPs) have the ability to kill resistant pathogens while diminishing the development of resistance. Citropin 1.1 (Cit 1.1) is an AMP effective against a broad range of pathogens. 20 analogues of Cit 1.1 were prepared to understand how sequence variations lead to changes in structure and biological activity. Various analogues exhibited an increased antimicrobial activity relative to Cit 1.1. The two most promising, AMP-016 (W3F) and AMP-017 (W3F, D4R, K7R) presented a 2-to 8-fold increase in activity against MRSA (both = 4 μg/mL). AMP-017 was active against E. coli (4 μg/mL), K. pneumoniae (8 μg/mL), and A. baumannii (2 μg/mL). NMR studies indicated that Cit 1.1 and its analogues form a head-to-tail helical dimer in a membrane environment, which differs from a prior study by Sikorska et al. Active peptides displayed a greater tendency to form α-helices and to dimerize when in contact with a negatively-charged membrane. Antimicrobial activity was observed to correlate to the overall stability of the α-helix and to a positively charged N-terminus. Biologically active AMPs were shown by SEM and flow cytometry to disrupt membranes in both Gram-positive and Gram-negative bacteria through a proposed carpet mechanism. Notably, active peptides exhibited typical serum stabilities and a good selectivity for bacterial cells over *

Alternating Cationic‐Hydrophobic Peptide/Peptoid Hybrids: Influence of Hydrophobicity on Antibacterial Activity and Cell Selectivity

“…This corroborates the trend that activity against E. coli is not promoted by increased hydrophobicity as also recently reported for similar peptidomimetics [8] . In relation to this replacement of the Phe residue in citropin 1.1 (i. e., GLFDVIKKVASVIGGL‐NH 2 ) with 2‐Nal or Bip resulted in analogues possessing almost unaltered activity against E. coli K12 [40] …”

Short Antimicrobial Peptide Derived from the Venom Gland Transcriptome of Pamphobeteus verdolaga Increases Gentamicin Susceptibility of Multidrug-Resistant Klebsiella pneumoniae

“…The observed 'blebbing effect' (Figure 1c,d), and a length of approximately 25 to 28 Å [77], strongly suggest that PvAMP66's antimicrobial effect is mediated through a carpet model mechanism of action [48,49]. Similar changes in morphology have been reported for IsCT (PvAMP66's homolog) and peptide AMP-016 on E. coli [78,79]. However, given the intricate interactions occurring within the peptide/phospholipid/transmembrane-protein complexes, additional research is needed to fully elucidate the complete mechanism of action of PvAMP66.…”

Synthesis of vancomycin fluorescent probes that retain antimicrobial activity, identify Gram-positive bacteria, and detect Gram-negative outer membrane damage

“…We developed two methods, using either flow cytometry or a plate reader for detection. E. coli ATCC 25922 was treated with 6 membraneactive antibiotics (tachyplesin-1 72 , arenicin-3 73 , polymyxin B 74 , colistin 75 , citropin 76 and octapeptin C4 77 ) and 3 membraneinactive antibiotics (gentamicin 78 : aminoglycoside 30S ribosome protein synthesis inhibitor; trimethoprim 79 : dihydrofolate reductase inhibitor, and erythromycin 80 : macrolide 50S ribosome protein synthesis inhibitor) at concentrations in range 0.125-128 µg/mL for 1 h, followed by labelling with the probe 9 (32 µg/mL). With the flow cytometry method (Fig.…”