TY - JOUR
T1 - Cyclic antimicrobial R-, W-rich peptides: the role of peptide structure and E. coli outer and inner membranes in activity and the mode of action
AU - Junkes, Christof
AU - Harvey, Richard D.
AU - Bruce, Kenneth D.
AU - Doelling, Rudolf
AU - Bagheri, Mojtaba
AU - Dathe, Margitta
PY - 2011/4
Y1 - 2011/4
N2 - This study compares the effect of cyclic R-, W-rich peptides with variations in amino acid sequences and sizes from 5 to 12 residues upon Gram negative and Gram positive bacteria as well as outer membrane-deficient and LPS mutant Escherichia coli (E. coli) strains to analyze the structural determinants of peptide activity. Cyclo-RRRWFW (c-WFW) was the most active and E. coli-selective sequence and bactericidal at the minimal inhibitory concentration (MIC). Removal of the outer membrane distinctly reduced peptide activity and the complete smooth LPS was required for maximal activity. c-WFW efficiently permeabilised the outer membrane of E. coli and promoted outer membrane substrate transport. Isothermal titration calorimetric studies with lipid A-, rough-LPS (r-LPS)- and smooth-LPS (s-LPS)-doped POPC liposomes demonstrated the decisive role of O-antigen and outer core polysaccharides for peptide binding and partitioning. Peptide activity against the inner E. coli membrane (IM) was very low. Even at a peptide to lipid ratio of 8/1, c-WFW was not able to permeabilise a phosphatidylglycerol/phosphatidylethanolamine (POPG/POPE) bilayer. Low influx of propidium iodide (PI) into bacteria confirmed a low permeabilising ability of c-WFW against PE-rich membranes at the MIC. Whilst the peptide effect upon eukaryotic cells correlated with the amphipathicity and permeabilisation of neutral phosphatidylcholine bilayers, suggesting a membrane disturbing mode of action, membrane permeabilisation does not seem to be the dominating antimicrobial mechanism of c-WFW. Peptide interactions with the LPS sugar moieties certainly modulate the transport across the outer membrane and are the basis of the E. coli selectivity of this type of peptides.
AB - This study compares the effect of cyclic R-, W-rich peptides with variations in amino acid sequences and sizes from 5 to 12 residues upon Gram negative and Gram positive bacteria as well as outer membrane-deficient and LPS mutant Escherichia coli (E. coli) strains to analyze the structural determinants of peptide activity. Cyclo-RRRWFW (c-WFW) was the most active and E. coli-selective sequence and bactericidal at the minimal inhibitory concentration (MIC). Removal of the outer membrane distinctly reduced peptide activity and the complete smooth LPS was required for maximal activity. c-WFW efficiently permeabilised the outer membrane of E. coli and promoted outer membrane substrate transport. Isothermal titration calorimetric studies with lipid A-, rough-LPS (r-LPS)- and smooth-LPS (s-LPS)-doped POPC liposomes demonstrated the decisive role of O-antigen and outer core polysaccharides for peptide binding and partitioning. Peptide activity against the inner E. coli membrane (IM) was very low. Even at a peptide to lipid ratio of 8/1, c-WFW was not able to permeabilise a phosphatidylglycerol/phosphatidylethanolamine (POPG/POPE) bilayer. Low influx of propidium iodide (PI) into bacteria confirmed a low permeabilising ability of c-WFW against PE-rich membranes at the MIC. Whilst the peptide effect upon eukaryotic cells correlated with the amphipathicity and permeabilisation of neutral phosphatidylcholine bilayers, suggesting a membrane disturbing mode of action, membrane permeabilisation does not seem to be the dominating antimicrobial mechanism of c-WFW. Peptide interactions with the LPS sugar moieties certainly modulate the transport across the outer membrane and are the basis of the E. coli selectivity of this type of peptides.
UR - http://www.scopus.com/inward/record.url?scp=79956024160&partnerID=8YFLogxK
U2 - 10.1007/s00249-011-0671-x
DO - 10.1007/s00249-011-0671-x
M3 - Conference paper
VL - 40
SP - 515
EP - 528
JO - European Biophysics Journal
JF - European Biophysics Journal
IS - 4
T2 - 455th Seminar on Biophysics of Membrane Active Peptides
Y2 - 11 April 2010 through 14 April 2010
ER -