SEMINAR: Understanding the action of antibacterials using neutrons
Professor Jeremy Lakey Institute for Cell and Molecular Biosciences The Medical School University of Newcastle
Location: Aud. 3, HCØ, Universitetsparken 5 Date and time: Thursday, September 19th – 10:00
Organiser: Associate Professor Karen martinez@nano.ku.dk
Gram-negative bacteria which include E. coli and the agents of Legionnaires disease, cholera and bubonic plague, possess an additional outer membrane (OM). This has a unique structure with lipopolysaccharide in the outer leaflet of the bilayer and phospholipids on the inner leaflet which face the periplasm that separates the OM from the more conventional inner membrane. The proteins of the OM are also unusual being almost exclusively beta-barrel in structure unlike the almost wholly alpha-helical structures of the inner membrane. The outer membrane protects bacteria from external stresses and is both a barrier to antimicrobial drugs and a source of vaccine components. We are interested in both areas but mostly in understanding how colicins, large proteins toxins produced by E. coli to fight competing bacteria, cross this OM on the way to killing their target 1. We have used neutron reflectivity at both the solid water 2 and air water interface to study the cross section of this membrane and SANS3 to resolve protein complexes. To enhance the resolution we have used selective deuteration of proteins, detergents and lipids plus, at the solid-water interface, magnetic contrast approaches 2. Recent work on lipopolysaccharide 4 and free standing bilayers as models of the outer membrane will also be presented
J.H. Lakey1, C.L. Johnson1, W. Arunmanee1, L.A Clifton2, A.P. LeBrun3 A. Hughes2, and S.A Holt3
1Institute for Cell and Molecular Biosciences, Newcastle University,NE2 4HH UK 2 ISIS, Rutherford Appleton Laboratory, Didcot, Oxfordshire, OX11 0QX, UK. 3Bragg Institute, ANSTO, Locked Bag 2001, Kirrawee DC, NSW 2232 Australia.
References
1.Baboolal, T. G., Conroy, M. J., Gill, K., Ridley, H., Visudtiphole, V., Bullough, P. A. & Lakey, J. H. (2008). Colicin N binds to the periphery of its receptor and translocator, outer membrane protein F. Structure 16, 371-379.
2. Holt, S. A., Le Brun, A. P., Majkrzak, C. F., McGillivray, D. J., Heinrich, F., Lösche, M. & Lakey, J. H. (2009). An ion channel containing model membrane: structural determination by magnetic contrast neutron reflectometry Soft Matter 5 2576 - 2586.
3. Clifton, L. A., Johnson, C. L., Solovyova, A. S., Callow, P., Weiss, K. L., Ridley, H., Le Brun, A. P., Kinane, C. J., Webster, J. R. P., Holt, S. A. & Lakey, J. H. (2012). Low Resolution Structure and Dynamics of a Colicin-Receptor Complex Determined by Neutron Scattering. Journal of Biological Chemistry 287, 337-346.
4. Le Brun, A. P., Clifton, L. A., Halbert, C. E., Lin, B., Meron, M., Holden, P. J., Lakey, J. H. & Holt, S. A. (2013). Structural Characterization of a Model Gram-Negative Bacterial Surface Using Lipopolysaccharides from Rough Strains of Escherichia coil. Biomacromolecules 14, 2014-2022.