Personne : Gomaa, Ahmed
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Gomaa
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Ahmed
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Département des sciences des aliments, Faculté des sciences de l'agriculture et de l'alimentation, Université Laval
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ncf11889114
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Publication Restreint Lasso-inspired peptides with distinct antibacterial mechanisms(Springer-Verlag Wien, 2014-12-04) Biron, Éric; Gomaa, Ahmed; Fliss, Ismaïl; Bédard, François; Subirade, Muriel; Hammami, RiadhAbstract Microcin J25 (MccJ25) is an antibacterial peptide with a peculiar molecular structure consisting of 21 amino acids and a unique lasso topology that makes it highly stable. We synthesized various MccJ25-derived peptides that retained some of the inhibitory activity of the native molecule against Salmonella enterica and Escherichia coli. Of the tested peptides, C1, 7-21C and WK_7-21 were the most inhibitory peptides (MIC = 1–250 µM), but all three were less potent than MccJ25. While MccJ25 was not active against Gram-positive bacteria, the three derived peptides were slightly inhibitory to Gram-positive bacteria (MIC = 250 µM). At 5 µM, C1, 7-21C and WK_7-21 reduced E. coli RNA polymerase activity by respectively, 23.4, 37.4 and 65.0 %. The MccJ25 and its derived peptides all appeared to affect the respiratory apparatus of S. enterica. Based on circular dichroism and FTIR spectroscopy, the peptides also interact with bacterial membrane phospholipids. These results suggest the possibility of producing potent MccJ25-derived peptides lacking the lasso structure. Keywords Antimicrobial peptides · Microcin J25 · Solid phase peptide synthesis · Antibacterial activity · Mode of actionPublication Restreint Collagencin, an antibacterial peptide from fish collagen : activity, structure and interaction dynamics with membrane(Elsevier, 2016-03-30) Biron, Éric; Gomaa, Ahmed; Fliss, Ismaïl; Beaulieu, Lucie; Bédard, François; Subirade, Muriel; Ennaas, Nadia; Hammami, RiadhIn this study, we first report characterization of collagencin, an antimicrobial peptide identified from fish collagen hydrolysate. The peptide completely inhibited the growth of Staphylococcus aureus at 1.88 mM. Although non-toxic up to 470 μM, collagencin was hemolytic at higher concentrations. The secondary structure of collagencin was mainly composed by β-sheet and β-turn as determined by CD measurements and molecular dynamics. The peptide is likely to form β-sheet structure under hydrophobic environments and interacts with both anionic (phosphatidylglycerol) and zwitterionic (phosphoethanolamine and phosphatidylcholine) lipids as shown with CD spectroscopy and molecular dynamics. The peptide formed several hydrogen bonds with both POPG and POPE lipids and remained at membrane–water interface, suggesting that collagencin antibacterial action follows a carpet mechanism. Collagenous fish wastes could be processed by enzymatic hydrolysis and transformed into products of high value having functional or biological properties. Marine collagens are a promising source of antimicrobial peptides with new implications in food safety and human health.