title: Investigating the effects of L- to D-amino acid substitution and deamidation on the activity and membrane interactions of antimicrobial peptide anoplin.
abstract: Isolated from the venom sac of solitary spider wasp, Anoplius samariensis, anoplin is the smallest linear α-helical antimicrobial peptide found naturally with broad spectrum activity against both Gram-positive and Gram-negative bacteria, and little hemolytic activity toward human erythrocytes. Deamidation was found to decrease the peptide's antibacterial properties. In the present work, interactions of amidated (Ano-NH2) and deamidated (Ano-OH) forms of anoplin as well as Ano-NH2 composed of all D-amino acids (D-Ano-NH2) with model cell membranes were investigated by means of Langmuir Blodgett (LB) technique, atomic force microscopy (AFM), X-ray photoemission electron microscopy (X-PEEM) and carboxyfluorescein leakage assay in order to gain a better understanding of the effect of these peptide modifications on membrane binding and lytic properties. According to LB, all three peptides form stable monolayers at the air/water interface with Ano-NH2 occupying a slightly greater area per molecule than Ano-OH. All three forms of the peptide interact preferentially with anionic 1,2-dipalmitoyl-sn-glycero-3-[phospho-rac-(1-glycerol)] (DPPG), rather than zwitterionic 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) lipid monolayer. Peptides form nanoscale clusters in zwitterionic but not in anionic monolayers. Finally, membrane lytic activity of all derivatives was found to depend strongly on membrane composition and lipid/peptide ratio. The results suggest that amidated forms of peptides are likely to possess higher membrane binding affinity due to the increased charge.
authors.affiliation: Department of Chemistry, Carleton University, 1125 Colonel By Dr. Ottawa, ON, Canada.
authors.forename: Amy
authors.initials: A
authors.lastname: Won
authors.forename: Mourin
authors.initials: M
authors.lastname: Khan
authors.forename: Sorin
authors.initials: S
authors.lastname: Gustin
authors.forename: Akuvi
authors.initials: A
authors.lastname: Akpawu
authors.forename: Deeptee
authors.initials: D
authors.lastname: Seebun
authors.forename: Tyler J
authors.initials: TJ
authors.lastname: Avis
authors.forename: Bonnie O
authors.initials: BO
authors.lastname: Leung
authors.forename: Adam P
authors.initials: AP
authors.lastname: Hitchcock
authors.forename: Anatoli
authors.initials: A
authors.lastname: Ianoul
mesh_terms: D015060:1,2-Dipalmitoylphosphatidylcholine / Q000737:chemistry / Q000378:metabolism; D000577:Amides / Q000378:metabolism; D019943:Amino Acid Substitution; D000818:Animals; D023181:Antimicrobial Cationic Peptides / Q000235:genetics* / Q000378:metabolism* / Q000494:pharmacology; D001412:Bacillus subtilis / Q000187:drug effects / Q000254:growth & development; D002462:Cell Membrane / Q000737:chemistry / Q000378:metabolism; D004926:Escherichia coli / Q000187:drug effects / Q000254:growth & development; D005452:Fluoresceins / Q000737:chemistry / Q000378:metabolism; D006461:Hemolysis / Q000187:drug effects; D006801:Humans; D006927:Hymenoptera / Q000378:metabolism; D008051:Lipid Bilayers / Q000737:chemistry / Q000378:metabolism; D018625:Microscopy, Atomic Force; D008854:Microscopy, Electron / Q000379:methods; D010715:Phosphatidylglycerols / Q000737:chemistry / Q000378:metabolism; D011485:Protein Binding; D014862:Wasp Venoms / Q000235:genetics* / Q000378:metabolism* / Q000494:pharmacology
chemical_list: D000577:Amides; D023181:Antimicrobial Cationic Peptides; D005452:Fluoresceins; D008051:Lipid Bilayers; D010715:Phosphatidylglycerols; D014862:Wasp Venoms; C443041:anoplin; D015060:1,2-Dipalmitoylphosphatidylcholine; C024098:6-carboxyfluorescein; C030345:1,2-dipalmitoylphosphatidylglycerol