title: HR-MAS NMR reveals a pH-dependent LPS alteration by de-O-acetylation at abequose in the O-antigen of Salmonella enterica serovar Typhimurium.
abstract: NMR spectroscopy can detect biomolecules like lipopolysaccharide directly on the surface of the cell, thus avoiding isolation and purification, and providing a more realistic description than the one derived from in vitro studies. Here we present a high-resolution magic-angle spinning NMR study of the O-antigen of Salmonella enterica serovar Typhimurium (S. Typhimurium) performed directly on the cells showing the alteration of its acetylation state over time. The O-antigen region of S. Typhimurium consists of the repeating unit [→2)-α-d-Manp-(1→4)-α-l-Rhap-(1→3)-α-d-Galp-(1→] where Man stands for mannose, Rha for rhamnose, and Gal for galactose. Man is substituted with abequose (Abe) O-acetylated at carbon 2. Our studies revealed that the appearance of de-O-acetylated O-antigen in the stationary growth phase is due to the de-O-acetylation of already synthesized O-acetylated O-antigen and that this reaction is caused by the metabolism-induced basic pH of the growth medium. The labile O-acetylation of the O-antigen we observed in S. Typhimurium generates non-stoichiometric O-acetylation states and therefore changes the nature of an immunogenic epitope.
authors.affiliation: Institute of Microbiology, ETH Zurich, Department of Biology, HCI F407, Wolfgang-Pauli-Str. 10, CH-8093 Zurich, Switzerland.
authors.forename: Karin
authors.initials: K
authors.lastname: Ilg
authors.forename: Giorgia
authors.initials: G
authors.lastname: Zandomeneghi
authors.forename: George
authors.initials: G
authors.lastname: Rugarabamu
authors.forename: Beat H
authors.initials: BH
authors.lastname: Meier
authors.forename: Markus
authors.initials: M
authors.lastname: Aebi
mesh_terms: D000107:Acetylation; D002240:Carbohydrate Sequence; D005690:Galactose / Q000494:pharmacology; D006601:Hexoses / Q000737:chemistry / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D008070:Lipopolysaccharides / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008969:Molecular Sequence Data; D019081:O Antigens / Q000737:chemistry* / Q000276:immunology / Q000378:metabolism; D012486:Salmonella typhimurium / Q000737:chemistry* / Q000187:drug effects / Q000254:growth & development / Q000276:immunology*
chemical_list: D006601:Hexoses; D008070:Lipopolysaccharides; D019081:O Antigens; C023708:abequose; D005690:Galactose
keywords: High-resolution MAS NMR; NMR; O-Acetylation; O-Antigen; Salmonella