Infections caused by Acinetobacter baumannii isolates from the major global clones, GC1 and GC2, are difficult to treat with antibiotics, and phage therapy, which requires extensive knowledge of the variation in the surface polysaccharides, is an option under consideration. The gene clusters directing the synthesis of capsular polysaccharide (CPS) in A. baumannii GC1 isolate A388 and GC2 isolate G21 differ by a single glycosyltransferase (gtr) gene. They include genes encoding a novel UDP-glucose dehydrogenase (Ugd2) and a putative pyruvyl transferase (Ptr2). The composition and structures of the linear K20 and K21 tetrasaccharide repeats (K units) of the CPSs isolated from A338 and G21, respectively, were established by sugar analyses and Smith degradation along with 1D and 2D 1H and 13C NMR spectroscopy. The K20 and K21 CPSs are the first known to include GlcpA produced by Ugd2 and d-galactose with an (R)-configured 4,6-pyruvic acid acetal added by Prt2. The first sugar in the tetrasaccharide K units is 2-acetamido-4-amino-2,4,6-trideoxy-d-glucose (d-QuipNAc4N) that carries a 4-N-[(S)-3-hydroxybutanoyl] group in some K units and a 4-N-acetyl group in the others. Accordingly, K unit polymerases WzyK20 and WzyK21 form a β-d-QuipNAc4NR-(1→2)-d-Galp bond. The K20 and K21 units differ only in the configuration of the glycosidic linkages of d-GlcpNAc allowing the unique inverting glycosyltransferases Gtr43 and the retaining glycosyltransferase Gtr45 to be assigned to the formation of the β-d-GlcpNAc-(1→4)-d-GlcpA and α-d-GlcpNAc-(1→4)-d-GlcpA linkages, respectively.
Acinetobacter baumannii, capsular polysaccharide, glucuronic acid, Pyruvic acid acetal, K locus
NCBI PubMed ID: 30107435Publication DOI: 10.1093/glycob/cwy074Journal NLM ID: 9104124Publisher: IRL Press at Oxford University Press
Correspondence: johanna.kenyon@qut.edu.au
Institutions: M. M. Shemyakin & Y. A. Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow, Russia, State Research Center for Applied Microbiology and Biotechnology, Obolensk, Moscow Region, Russia, N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, 47 Leninskii prosp., Moscow, Russia, Higher Chemical College of the Russian Academy of Sciences, D. I. Mendeleev University of Chemical Technology of Russia, 9 Miusskaya pl., Moscow, Russia, School of Molecular Bioscience, The University of Sydney, Cnr of Maze Cres and Butlin Ave, Darlington Campus, Sydney, Australia, Institute of Health and Biomedical Innovation, School of Biomedical Sciences, Faculty of Health, Queensland University of Technology, 60 Musk Ave, Kelvin Grove, Brisbane, Australia, Moscow Institute of Physics and Technology, 9 Institutskii per., Dolgoprudny, Moscow Region, Russia, School of Life and Environmental Sciences, The University of Sydney, Cnr of Maze Cres and Butlin Ave, Darlington Campus, Sydney, Australia
Methods: 13C NMR, 1H NMR, NMR-2D, sugar analysis, acid hydrolysis, GLC, Smith degradation, GPC, bioinformatic analysis (BLASTp)
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