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Structure type: monomer
Trivial name: GDP-4-keto-6-deoxy-D-lyxo-heptose, GDP-6-deoxy-4-keto-D-lyxo-heptose
Compound class: nucleoside diphosphate sugar
Contained glycoepitopes: IEDB_141493,IEDB_149170,IEDB_190357

• Article ID: 3479
  Ho N, Kondakova AN, Knirel YA, Creuzenet C "The biosynthesis and biological role of 6-deoxyheptoses in the lipopolysaccharide O-antigen of Yersinia pseudotuberculosis" - Molecular Microbiology 68(2) (2008) 424-447
  

  Yersinia pseudotuberculosis O:2a harbours 6-deoxy-d-manno-heptose in its O-antigen. The biological function of 6-deoxyheptose and its role in virulence is unknown and its biosynthetic pathway has not been demonstrated experimentally. Here, we show that dmhA and dmhB are necessary for 6-deoxyheptose biosynthesis in Y. pseudotuberculosis. Their disruption resulted in the lack of 6-deoxyheptose in the O-unit and its replacement by d-glycero-d-manno-heptose, thus indicating relaxed specificity of the glycosyltransferases, polymerase and ligase involved in lipopolysaccharide synthesis. The dmhB mutant exhibited a lower content in ketooctonic acid (Ko)-containing core molecules and reduced ligation and polymerization of the O-unit. We also show that Tyr128 is essential for activity of DmhB, and that DmhB functions as an oligomer, based on the dominant negative effect of overexpression of DmhB Y128F in dmhA. Moreover, we demonstrate that 6-deoxyheptose is important for virulence-related functions of the outer membrane and its appendages in vitro, such as barrier function against bile salts, polymyxin and novobiocin, and flagella-mediated motility. Although both mutants colonized the mouse ceacum as well as the wild type, the dmhB mutant was impaired for colonization of the liver, suggesting that DmhB represents a potential therapeutic target.

  Lipopolysaccharide, biosynthesis, O-antigen, Yersinia pseudotuberculosis, structural studies, 6-deoxyheptose

  NCBI PubMed ID: 18284593
  Journal NLM ID: 8712028
  Publisher: Blackwell Publishing
  Correspondence: ccreuzen@uwo.ca
  Institutions: Department of Microbiology and Immunology, Infectious Diseases Research Group, University of Western Ontario, London, Ontario, Canada.
  Methods: 13C NMR, 1H NMR, NMR-2D, ESI-MS, serological methods, genetic methods
  
   
  
  Yersinia pseudotuberculosis O2a
  CSDB ID 22977 (all data & tools)
• Article ID: 5478
  McCallum M, Shaw SD, Shaw GS, Creuzenet C "Complete 6-deoxy-D-altro-heptose biosynthesis pathway from Campylobacter jejuni: more complex than anticipated" - Journal of Biological Chemistry 287(35) (2012) 29776-29788
  

  The Campylobacter jejuni capsule is important for colonization and virulence in various infection models. In most strains, the capsule includes a modified heptose whose biological role and biosynthetic pathway are unknown. To decipher the biosynthesis pathway for the 6-deoxy-D-altro-heptose of strain 81-176, we previously showed that the 4,6-dehydratase WcbK and the reductase WcaG generated GDP-6-deoxy-D-manno-heptose, but the C3 epimerase necessary to form GDP-6-deoxy-D-altro-heptose was not identified. Herein, we characterized the putative C3/C5 epimerase Cjj1430 and C3/C5 epimerase/C4 reductase Cjj1427 from the capsular cluster. We demonstrate that GDP-6-deoxy-D-altro-heptose biosynthesis is more complex than anticipated and requires the sequential action of WcbK, Cjj1430, and Cjj1427. We show that Cjj1430 serves as C3 epimerase devoid of C5 epimerization activity and that Cjj1427 has no epimerization activity and only serves as a reductase to produce GDP-6-deoxy-D-altro-heptose. Cjj1430 and Cjj1427 are the only members of the C3/C5 epimerases and C3/C5 epimerase/C4 reductase families shown to have activity on a heptose substrate and to exhibit only one of their two to three potential activities, respectively. Furthermore, we show that although the reductase WcaG is not part of the main pathway, its presence and its product affect the outcome of the pathway in a complex regulatory loop involving Cjj1427. This work provides the grounds for the elucidation of similar pathways found in other C. jejuni strains and other pathogens. It provides new molecular tools for the synthesis of carbohydrate antigens useful for vaccination and for the screening of enzymatic inhibitors that may have antibacterial effects.

  Campylobacter, Enzymes, carbohydrate biosynthesis, Capsule Synthesis, Epimerases, GDP-6-Deoxy-altro-heptose, Heptose Modification, Microbial Pathogenesis

  NCBI PubMed ID: 22787156
  Publication DOI: 10.1074/jbc.M112.390492
  Journal NLM ID: 2985121R
  Publisher: Baltimore, MD: American Society for Biochemistry and Molecular Biology
  Correspondence: ccreuzen@uwo.ca
  Institutions: Department of Microbiology and Immunology, Infectious Diseases Research Group, University of Western Ontario, London, Ontario N6A 5C1, Canada
  Methods: 13C NMR, 1H NMR, NMR-2D, DNA cloning, DNA techniques, MALDI-MS, MS/MS, biochemical methods, enzyme assay, CE, anion exchange chromatography
  
   
  
  Campylobacter jejuni 81-176
  CSDB ID 1979 (all data & tools)