title: The lbgAB gene cluster of Haemophilus ducreyi encodes a beta-1,4-galactosyltransferase and an alpha-1,6-DD-heptosyltransferase involved in lipooligosaccharide biosynthesis.
abstract: All Haemophilus ducreyi strains examined contain a lipooligosaccharide (LOS) consisting of a single but variable branch oligosaccharide that emanates off the first heptose (Hep-I) of a conserved Hep(3)-phosphorylated 3-deoxy-D-manno-octulosonic acid-lipid A core. In a previous report, identification of tandem genes, lbgA and lbgB, that are involved in LOS biosynthesis was described (Stevens et al., Infect. Immun. 65:651-660, 1997). In a separate study, the same gene cluster was identified and the lbgB (losB) gene was found to be required for transfer of the second sugar, D-glycero-D-manno-heptose (DD-Hep), of the major branch structure (Gibson et al., J. Bacteriol. 179:5062-5071, 1997). In this study, we identified the function of the neighboring upstream gene, lbgA, and found that it is necessary for addition of the third sugar in the dominant oligosaccharide branch, a galactose-linked beta1-->4, to the DD-Hep. LOS from an lbgA mutant and an lbgAB double mutant were isolated and were characterized by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, carbohydrate analysis, mass spectrometry, and nuclear magnetic resonance spectroscopy. The results showed that the mutant strains synthesize truncated LOS glycoforms that terminate after addition of the first glucose (lbgAB) or the disaccharide DD-Hepalpha1-->6Glcbeta1 (lbgA) that is attached to the heptose core. Both mutants show a significant reduction in the ability to adhere to human keratinocytes. Although minor differences were observed after two-dimensional gel electrophoresis of total proteins from the wild-type and mutant strains, the expression levels of the vast majority of proteins were unchanged, suggesting that the differences in adherence and invasion are due to differences in LOS. These studies add to the mounting evidence for a role of full-length LOS structures in the pathophysiology of H. ducreyi infection.
authors: Department of Pharmaceutical Chemistry, University of California, San Francisco, California 94143-0446, USA.
authors: Michael V
authors: MV
authors: Tullius
authors: Nancy J
authors: NJ
authors: Phillips
authors: N Karoline
authors: NK
authors: Scheffler
authors: Nicole M
authors: NM
authors: Samuels
authors: Robert S
authors: RS
authors: Munson Jr
authors: Eric J
authors: EJ
authors: Hansen
authors: Marla
authors: M
authors: Stevens-Riley
authors: Anthony A
authors: AA
authors: Campagnari
authors: Bradford W
authors: BW
authors: Gibson
mesh_terms: D000215:Acylation; D001422:Bacterial Adhesion; D001426:Bacterial Proteins; D002240:Carbohydrate Sequence; D004187:Disaccharides; D004591:Electrophoresis, Polyacrylamide Gel / Q000379:methods; D005798:Genes, Bacterial / Q000502:physiology*; D016695:Glycosyltransferases / Q000235:genetics / Q000378:metabolism*; D006191:Haemophilus ducreyi / Q000201:enzymology* / Q000235:genetics / Q000502:physiology; D015603:Keratinocytes / Q000382:microbiology; D008070:Lipopolysaccharides / Q000096:biosynthesis*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D008969:Molecular Sequence Data; D005810:Multigene Family / Q000502:physiology*; D009237:N-Acetyllactosamine Synthase / Q000235:genetics / Q000378:metabolism*; D009844:Oligosaccharides; D012967:Sodium Dodecyl Sulfate; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods
chemical_list: D001426:Bacterial Proteins; D004187:Disaccharides; D008070:Lipopolysaccharides; D009844:Oligosaccharides; C023023:lipid-linked oligosaccharides; D012967:Sodium Dodecyl Sulfate; D016695:Glycosyltransferases; C457419:lbgB protein, H ducreyi; D009237:N-Acetyllactosamine Synthase; C457399:lbgA protein, Haemophilus ducreyi