title: Structural analysis of the core region of O-lipopolysaccharide of Porphyromonas gingivalis from mutants defective in O-antigen ligase and O-antigen polymerase.
abstract: Porphyromonas gingivalis synthesizes two lipopolysaccharides (LPSs), O-LPS and A-LPS. Here, we elucidate the structure of the core oligosaccharide (OS) of O-LPS from two mutants of P. gingivalis W50, Delta PG1051 (WaaL, O-antigen ligase) and Delta PG1142 (O-antigen polymerase), which synthesize R-type LPS (core devoid of O antigen) and SR-type LPS (core plus one repeating unit of O antigen), respectively. Structural analyses were performed using one-dimensional and two-dimensional nuclear magnetic resonance spectroscopy in combination with composition and methylation analysis. The outer core OS of O-LPS occurs in two glycoforms: an "uncapped core," which is devoid of O polysaccharide (O-PS), and a "capped core," which contains the site of O-PS attachment. The inner core region lacks L(D)-glycero-D(l)-manno-heptosyl residues and is linked to the outer core via 3-deoxy-D-manno-octulosonic acid, which is attached to a glycerol residue in the outer core via a monophosphodiester bridge. The outer region of the "uncapped core" is attached to the glycerol and is composed of a linear alpha-(1-->3)-linked d-Man OS containing four or five mannopyranosyl residues, one-half of which are modified by phosphoethanolamine at position 6. An amino sugar, alpha-D-allosamine, is attached to the glycerol at position 3. In the "capped core," there is a three- to five-residue extension of alpha-(1-->3)-linked Man residues glycosylating the outer core at the nonreducing terminal residue. beta-D-GalNAc from the O-PS repeating unit is attached to the nonreducing terminal Man at position 3. The core OS of P. gingivalis O-LPS is therefore a highly unusual structure, and it is the basis for further investigation of the mechanism of assembly of the outer membrane of this important periodontal bacterium.
authors.affiliation: Queen Mary University of London, Barts and The London School of Medicine and Dentistry, Centre for Infectious Disease, Institute of Cell and Molecular Science, 4 Newark Street, London E1 2AT, United Kingdom.
authors.forename: Nikolay A
authors.initials: NA
authors.lastname: Paramonov
authors.forename: Joseph
authors.initials: J
authors.lastname: Aduse-Opoku
authors.forename: Ahmed
authors.initials: A
authors.lastname: Hashim
authors.forename: Minnie
authors.initials: M
authors.lastname: Rangarajan
authors.forename: Michael A
authors.initials: MA
authors.lastname: Curtis
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000502:physiology*; D015153:Blotting, Western; D002240:Carbohydrate Sequence; D004591:Electrophoresis, Polyacrylamide Gel; D006602:Hexosyltransferases / Q000235:genetics / Q000502:physiology*; D008070:Lipopolysaccharides / Q000737:chemistry* / Q000378:metabolism*; D009682:Magnetic Resonance Spectroscopy; D008969:Molecular Sequence Data; D016966:Porphyromonas gingivalis / Q000235:genetics* / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D008070:Lipopolysaccharides; D006602:Hexosyltransferases; C085652:O-antigen polymerase