title: The Effect of Lipopolysaccharide Core Oligosaccharide Size on the Electrostatic Binding of Antimicrobial Proteins to Models of the Gram Negative Bacterial Outer Membrane.
abstract: Understanding the electrostatic interactions between bacterial membranes and exogenous proteins is crucial to designing effective antimicrobial agents against Gram-negative bacteria. Here we study, using neutron reflecometry under multiple isotopic contrast conditions, the role of the uncharged sugar groups in the outer core region of lipopolysaccharide (LPS) in protecting the phosphate-rich inner core region from electrostatic interactions with antimicrobial proteins. Models of the asymmetric Gram negative outer membrane on silicon were prepared with phopshatidylcholine (PC) in the inner leaflet (closest to the silicon), whereas rough LPS was used to form the outer leaflet (facing the bulk solution). We show how salt concentration can be used to reversibly alter the binding affinity of a protein antibiotic colicin N (ColN) to the anionic LPS confirming that the interaction is electrostatic in nature. By examining the interaction of ColN with two rough LPS types with different-sized core oligosaccharide regions we demonstrate the role of uncharged sugars in blocking short-range electrostatic interactions between the cationic antibiotics and the vulnerable anionic phosphate groups.
authors.affiliation: ISIS Pulsed Neutron and Muon Source, Science and Technology Facilities Council, Rutherford Appleton Laboratory , Harwell Science and Innovation Campus, Didcot, Oxfordshire, OX11 OQX, United Kingdom.
authors.forename: Luke A
authors.initials: LA
authors.lastname: Clifton
authors.affiliation: Department of Plant Sciences, University of Oxford , Oxford, OX1 3RB, United Kingdom.
authors.forename: Filip
authors.initials: F
authors.lastname: Ciesielski
authors.affiliation: ISIS Pulsed Neutron and Muon Source, Science and Technology Facilities Council, Rutherford Appleton Laboratory , Harwell Science and Innovation Campus, Didcot, Oxfordshire, OX11 OQX, United Kingdom.
authors.forename: Maximilian W A
authors.initials: MW
authors.lastname: Skoda
authors.affiliation: Institute for Cell and Molecular Biosciences, Newcastle University , Framlington Place, Newcastle upon Tyne, NE2 4HH, United Kingdom.
authors.forename: Nicolò
authors.initials: N
authors.lastname: Paracini
authors.affiliation: Bragg Institute, Australian Nuclear Science and Technology Organisation , Locked Bag 2001, Kirrawee DC, New South Wales 2232, Australia.
authors.forename: Stephen A
authors.initials: SA
authors.lastname: Holt
authors.affiliation: Institute for Cell and Molecular Biosciences, Newcastle University , Framlington Place, Newcastle upon Tyne, NE2 4HH, United Kingdom.
authors.forename: Jeremy H
authors.initials: JH
authors.lastname: Lakey
mesh_terms: D015060:1,2-Dipalmitoylphosphatidylcholine / Q000737:chemistry; D002462:Cell Membrane / Q000737:chemistry*; D003087:Colicins / Q000737:chemistry*; D004926:Escherichia coli / Q000737:chemistry* / Q000235:genetics; D008051:Lipid Bilayers / Q000737:chemistry*; D008070:Lipopolysaccharides / Q000737:chemistry*; D033363:Neutron Diffraction; D009844:Oligosaccharides / Q000737:chemistry*; D011485:Protein Binding; D055672:Static Electricity
chemical_list: D003087:Colicins; D008051:Lipid Bilayers; D008070:Lipopolysaccharides; D009844:Oligosaccharides; D015060:1,2-Dipalmitoylphosphatidylcholine