title: A coiled-coil domain acts as a molecular ruler to regulate O-antigen chain length in lipopolysaccharide.
abstract: Long-chain bacterial polysaccharides have important roles in pathogenicity. In Escherichia coli O9a, a model for ABC transporter-dependent polysaccharide assembly, a large extracellular carbohydrate with a narrow size distribution is polymerized from monosaccharides by a complex of two proteins, WbdA (polymerase) and WbdD (terminating protein). Combining crystallography and small-angle X-ray scattering, we found that the C-terminal domain of WbdD contains an extended coiled-coil that physically separates WbdA from the catalytic domain of WbdD. The effects of insertions and deletions in the coiled-coil region were analyzed in vivo, revealing that polymer size is controlled by varying the length of the coiled-coil domain. Thus, the coiled-coil domain of WbdD functions as a molecular ruler that, along with WbdA:WbdD stoichiometry, controls the chain length of a model bacterial polysaccharide.
authors.affiliation: Biomedical Sciences Research Complex, University of St Andrews, St Andrews, Fife, KY16 9ST, UK.|Institute for Physical and Theoretical Chemistry, University of Bonn, Wegelerstr. 12, 53115 Bonn, Germany.
authors.forename: Gregor
authors.initials: G
authors.lastname: Hagelueken
authors.affiliation: Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario, N1G 2W1, Canada.
authors.forename: Bradley R
authors.initials: BR
authors.lastname: Clarke
authors.affiliation: Biomedical Sciences Research Complex, University of St Andrews, St Andrews, Fife, KY16 9ST, UK.
authors.forename: Hexian
authors.initials: H
authors.lastname: Huang
authors.affiliation: European Molecular Biology Laboratory, Hamburg Outstation, Notkestraße 85, 22603 Hamburg, Germany.
authors.forename: Anne
authors.initials: A
authors.lastname: Tuukkanen
authors.affiliation: European Molecular Biology Laboratory, Hamburg Outstation, Notkestraße 85, 22603 Hamburg, Germany.
authors.forename: Iulia
authors.initials: I
authors.lastname: Danciu
authors.affiliation: European Molecular Biology Laboratory, Hamburg Outstation, Notkestraße 85, 22603 Hamburg, Germany.
authors.forename: Dmitri I
authors.initials: DI
authors.lastname: Svergun
authors.affiliation: Diamond Light Source, Didcot, OX11 0QX, UK.
authors.forename: Rohanah
authors.initials: R
authors.lastname: Hussain
authors.affiliation: Biomedical Sciences Research Complex, University of St Andrews, St Andrews, Fife, KY16 9ST, UK.
authors.forename: Huanting
authors.initials: H
authors.lastname: Liu
authors.affiliation: Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario, N1G 2W1, Canada.
authors.forename: Chris
authors.initials: C
authors.lastname: Whitfield
authors.affiliation: Biomedical Sciences Research Complex, University of St Andrews, St Andrews, Fife, KY16 9ST, UK.
authors.forename: James H
authors.initials: JH
authors.lastname: Naismith
mesh_terms: D018360:Crystallography, X-Ray; D004926:Escherichia coli / Q000737:chemistry* / Q000201:enzymology*; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000378:metabolism*; D008070:Lipopolysaccharides / Q000737:chemistry / Q000378:metabolism; D008364:Mannosyltransferases / Q000737:chemistry / Q000378:metabolism; D019081:O Antigens / Q000737:chemistry* / Q000378:metabolism*; D011487:Protein Conformation; D053838:Scattering, Small Angle
chemical_list: D029968:Escherichia coli Proteins; D008070:Lipopolysaccharides; D019081:O Antigens; C000595910:WbdD protein, E coli; D008364:Mannosyltransferases; C577535:WbdA protein, E coli