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Structure type: oligomer
Trivial name: O-methyl glycoside
Compound class: O-antigen

• Article ID: 5848
  Speciale I, Di Lorenzo F, Gargiulo V, Erbs G, Newman MA, Molinaro A, De Castro C "Biopolymer Skeleton Produced by Rhizobium radiobacter: Stoichiometric Alternation of Glycosidic and Amidic Bonds in the Lipopolysaccharide O-Antigen" - Angewandte Chemie, International Edition 59(16) (2020) 6368-6374
  

  The lipopolysaccharide (LPS) O-antigen structure of the plant pathogen Rhizobium radiobacter strain TT9 and its possible role in a plant-microbe interaction was investigated. The analyses disclosed the presence of two O-antigens, named Poly1 and Poly2. The repetitive unit of Poly2 constitutes a 4-α-l-rhamnose linked to a 3-α-d-fucose residue. Surprisingly, Poly1 turned out to be a novel type of biopolymer in which the repeating unit is formed by a monosaccharide and an amino-acid derivative, so that the polymer has alternating glycosidic and amidic bonds joining the two units: 4-amino-4-deoxy-3-O-methyl-d-fucose and (2'R,3'R,4'S)-N-methyl-3',4'-dihydroxy-3'-methyl-5'-oxoproline). Differently from the O-antigens of LPSs from other pathogenic Gram-negative bacteria, these two O-antigens do not activate the oxidative burst, an early innate immune response in the model plant Arabidopsis thaliana, explaining at least in part the ability of this R. radiobacter strain to avoid host defenses during a plant infection process.

  carbohydrates, structure elucidation, saccharides, structural biology, Biopolymers

  NCBI PubMed ID: 32073204
  Publication DOI: 10.1002/anie.201914053
  Journal NLM ID: 0370543
  Publisher: Weinheim: Wiley-VCH
  Correspondence: molinaro@unina.it; decastro@unina.it
  Institutions: Department of Chemical Sciences, University of Napoli, Via Cintia 4, 80126, Napoli, Italy, Institute for Research on Combustion (IRC), CNR, Naples (Italy), Piazzale Vincenzo Tecchio 80, 80126, Napoli, Italy, Department of Health Technology, Technical University of Denmark, Kemitorvet, 2800 Kgs., Lyngby, Denmark, Department of Plant and Environmental Sciences, Faculty of Science, University of Copenhagen, Thorvaldsensvej 40, 1871, Frederiksberg, Denmark, Department of Agricultural Sciences, University of Napoli, Via Universita 100, 80055, Portici (NA), Italy
  Methods: periodate oxidation, GLC-MS, GC-MS, NMR, SDS-PAGE, Smith degradation, MD simulations, composition analysis, molecular mechanics, SEC, reduction with NaBH4, RP-HPLC, strong alkaline hydrolysis
  
   
  
  Rhizobium radiobacter TT9
  CSDB ID 7580 (all data & tools)