Journal
BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES
Volume 1798, Issue 6, Pages 1272-1280Publisher
ELSEVIER SCIENCE BV
DOI: 10.1016/j.bbamem.2010.03.012
Keywords
Lipid clustering; Antibacterial peptides; Membrane domains; Bacterial species specificity; Freeze fracture electron microscopy; Differential scanning calorimetry
Categories
Funding
- Canadian Institutes of Health Research [MOP 86608]
- Jeanne and Joseph Nissim Foundation for Life Sciences Research
- UNEMED of the University of Nebraska Medical Center
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Three Arg-rich nonapeptides, containing the same amino acid composition but different sequences, PFWRIRIRR-amide (PR-9), RRPFWIIRR-amide (RR-9) and PRFRWRIRI-amide (PI-9), are able to induce segregation of anionic lipids from zwitterionic lipids, as shown by changes in the phase transition properties of lipid mixtures detected by differential scanning calorimetry and freeze fracture electron microscopy. The relative Minimal Inhibitory Concentration (MIC) of these three peptides against several strains of Gram positive bacteria correlated well with the extent to which the lipid composition of the bacterial membrane facilitated peptide-induced clustering of anionic lipids. The lower activity of these three peptides against Gram negative bacteria could be explained by the retention of these peptides in the LPS layer. The membrane morphologies produced by PR-9 as well as by a cathelicidin fragment. KR-12 that had previously been shown to induce anionic lipid clustering, was directly visualized using freeze fracture electron microscopy. This work shows the insensitivity of phase segregation to the specific arrangement of the cationic charges in the peptide sequence as well as to their tendency to form different secondary structures. It also establishes the role of anionic lipid clustering in the presence of zwitterionic lipids in determining antimicrobial selectivity. (C) 2010 Elsevier B.V. All rights reserved.
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