title: Effect of cholesterol on the membrane interaction of Modelin-5 isoforms.
abstract: Modelin-5 isoforms were used to gain an insight into the effects of amidation on antimicrobial selectivity. When tested against Escherichia coli, amidation increased toxicity 10-fold (MIC = 31.25 μM) while showing limited increased hemolytic activity (2% lysis). Our results show that both the amidated and non-amidated peptides had a disordered structure in aqueous solution (<18% helical) and folded to form helices at the membrane interface (for example, >43% in the presence of DMPC). The stabilization of the helical structure by amidation has previously been shown to play a key role in increasing antibacterial efficacy. The presence of cholesterol in the membrane increases the packing density (C(s)(-1) values 25-33 mN m(-1)) and so prevents the peptide from forming stable association with the membrane, which is evidenced by the higher binding coefficient (K(d)) in the presence of cholesterol: 57.70 μM for Modelin-5-COOH and 35.64 μM for Modelin-5-CONH(2) compared to the presence of E. coli lipid extract (10 μM), which would prevent local concentration of the peptide at the bilayer interface as seen by reduction in monolayer interaction. This in turn would be predicted to inhibit activity.
authors.affiliation: School of Pharmacy and Biomedical Sciences, University of Central Lancashire, Preston PR1 2HE, UK.
authors.forename: Sarah R
authors.initials: SR
authors.lastname: Dennison
authors.forename: David A
authors.initials: DA
authors.lastname: Phoenix
mesh_terms: D000577:Amides / Q000009:adverse effects / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D000818:Animals; D000900:Anti-Bacterial Agents / Q000009:adverse effects / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D023181:Antimicrobial Cationic Peptides / Q000009:adverse effects / Q000737:chemistry* / Q000378:metabolism* / Q000494:pharmacology; D002784:Cholesterol / Q000737:chemistry* / Q000378:metabolism*; D002942:Circular Dichroism; D004355:Drug Stability; D004912:Erythrocytes / Q000187:drug effects / Q000378:metabolism; D004926:Escherichia coli / Q000187:drug effects; D006461:Hemolysis / Q000187:drug effects; D006801:Humans; D007700:Kinetics; D008081:Liposomes; D008566:Membranes / Q000737:chemistry* / Q000378:metabolism*; D008826:Microbial Sensitivity Tests; D017510:Protein Folding; D055550:Protein Stability; D017433:Protein Structure, Secondary; D034421:Sus scrofa; D013816:Thermodynamics
chemical_list: D000577:Amides; D000900:Anti-Bacterial Agents; D023181:Antimicrobial Cationic Peptides; D008081:Liposomes; C089690:modelin 5; D002784:Cholesterol