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References to other databases: GTC:G00051MO, GlycomeDB:48
Structural formula & atomic coordinates
Sweet-II 3D model
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The lipopolysaccharide of certain strains of Helicobacter pylori was recently shown to contain the Lewis X (Lex) trisaccharide (Galβ-1,4-(Fucα(1,3))-GlcNAc). Lex is an oncofetal antigen which appears on human gastric epithelium, and its mimicry by carbohydrate structures on the surface of H. pylori may play an important part in the interaction of this pathogen with its host. Potential roles for bacterial Lex in mucosal adhesion, immune evasion, and autoantibody induction have been proposed (Moran, A. P., Prendergast, M. M., and Appelmelk, B. J. (1996) FEMS Immunol. Med. Microbiol. 16, 105-115). In mammals, the final step of Lex biosynthesis is the α(1,3)-fucosylation of GlcNAc in a terminal Galβ(1→4)GlcNAc unit, and a corresponding GDP-fucose:N-acetylglucosaminyl α(1,3) fucosyltransferase (α(1,3)-Fuc-T) activity was recently discovered in H. pylori extracts. We used part of a human α(1, 3)-Fuc-T amino acid sequence to search an H. pylori genomic data base for related sequences. Using a probe based upon weakly matching data base sequences, we retrieved clones from a plasmid library of H. pylori DNA. DNA sequence analysis of the library clones revealed a gene which we have named fucT, encoding a protein with localized homology to the human α(1,3)-Fuc-Ts. We have demonstrated that fucT encodes an active Fuc-T enzyme by expressing the gene in Escherichia coli. The recombinant enzyme shows a strong preference for type 2 (e.g. LacNAc) over type 1 (e.g. lacto-N-biose) acceptors in vitro. Certain residues in a short segment of the H. pylori protein are completely conserved throughout the α(1,3)-Fuc-T family, defining an α(1,3)-Fuc-T motif which may be of use in identifying new fucosyltransferase genes.

Lipopolysaccharide, biosynthesis, LPS, O-antigen, transferase, Helicobacter pylori, Helicobacter, L-fucose, Lewis, Lewis x

NCBI PubMed ID: 9261148
Journal NLM ID: 2985121R
Publisher: Baltimore, MD: American Society for Biochemistry and Molecular Biology
Correspondence: slm17885@ggr.co.uk
Institutions: Glycobiology Unit and the Advanced Technologies and Informatics Unit, GlaxoWellcome Medicines Research Centre, Stevenage, Herts SGl, NY, United Kingdom and the Department of Medical Chemistry, Vrije Universiteit, Amsterdam, The Netherlands.

Helicobacter pylori NCTC11637 lipopolysaccharide (LPS) expresses the human blood group antigens Lewis x (Lex), Ley, and H type I. In this report, we demonstrate that the H type I epitope displays high-frequency phase variation. One variant expressed Lex and Ley and no H type I as determined by serology; this switch was reversible. Insertional mutagenesis in NCTC11637 of JHP563 (a poly(C) tract containing an open reading frame homologous to glycosyltransferases) yielded a transformant with a serotype similar to the phase variant. Structural analysis of the NCTC11637 LPS confirmed the loss of the H type I epitope. Sequencing of JHP563 in strains NCTC11637, an H type I-negative variant, and an H type I-positive switchback variant showed a C14 (gene on), C13 (gene off), and C14 tract, respectively. Inactivation of strain G27, which expresses Lex, Ley, H type I, and Lea, yielded a transformant that expressed Lex and Ley. We conclude that JHP563 encodes a b3-galactosyltransferase involved in the biosynthesis of H type I and Lea and that phase variation in H type I is due to C-tract changes in this gene. A second H type I-negative variant (variant 3a) expressed Lex and Lea and had lost both H type I and Ley expression. Inactivation of HP093-HP094 resulted in a transformant expressing Lex and lacking Ley and H type I. Structural analysis of a mutant LPS confirmed the serological data. We conclude that the HP093-HP094 a2-fucosyltransferase (a2-Fuct) gene product is involved in the biosynthesis of both Ley and Lex. Finally, we inactivated HP0379 in strain 3a. The transformant had lost both Lex and Lea expression, which demonstrates that the HP0379 gene product is both an a3- and an a4-FucT. Our data provide understanding at the molecular level of how H. pylori is able to diversify in the host, a requirement likely essential for successful colonization and transmission.

Lipopolysaccharide, Phase variation, gene, phase, tract, variation, epitope, type, epitopes, Helicobacter pylori, Helicobacter, change, Lewis, fucosyltransferase, Lewis a

NCBI PubMed ID: 10992504
Journal NLM ID: 0246127
Publisher: American Society for Microbiology
Correspondence: BJ.Appelmelk.mm@med.vu.nl
Institutions: Department of Medical Microbiology, Vrije Universiteit, Medical School, 1081 BT Amsterdam, The Netherlands, IRIS Research Center, Chiron SpA, Siena, Laboratory Unit, City Hospital, Brescia, Italy, National Research Council, Ottawa, Canada, Isosep, Tullinge, Sweden
Methods: PCR, DNA sequencing, FAB-MS, ELISA, MAb studies, insertional mutagenesis

In contrast to other Helicobacter pylori strains, which have serologically detectable Lewis(x)+ (Le(x)) and Lewis(y)++ (++Le(y)) antigenic determinants in the O-specific polysaccharide chains of the lipopolysaccharides, H. pylori AF1 and 007 were non-typable with anti-Le(x) and anti-Le(y) antibodies. The carbohydrate portions of the lipopolysaccharides were liberated by mild acid hydrolysis and subsequently studied by sugar and methylation analyses, 1H NMR spectroscopy and electrospray ionization-mass spectrometry. Compared with each other, and with lipopolysaccharides of strains studied previously, the lipopolysaccharides of both AF1 and 007 showed similarities, but also differences, in the structures of the core region and O-specific polysaccharide chains. The O-specific polysaccharide chains of both strains consisted of a short or long polyfucosylated poly-N-acetyl-β-lactosamine chains, which were distinguished from those of other strains by a high degree of fucosylation producing a polymeric Le(x)chain terminating with Le(x) or Le(y) units:[sequence: see text] where n = 0 or 1 in strain AF1 and 0 in strain 007, m = 0-2, 6-7 in strain AF1 and m = 0-2, 6-7 or approximately 40 in strain 007, the medium-size species being predominant. Therefore, compared with other strains, the lack of reactivity of lipopolysaccharide of H. pylori AF1 and 007 with anti-Le(x) and anti-Le(y) may reflect the presence of a polymeric Le(x) chain and has important implications for serological and pathogenesis studies. As the substitution pattern of a D-glycero-D-manno-heptose residue in the outer core varied in the two strains, and an extended DD-heptan chain was present in some lipopolysaccharide species but not in others, this region was less conservative than the inner core region. The inner core L-glycero-D-manno-heptose region of both strains carried a 2-aminoethyl phosphate group, rather than a phosphate group, as reported previously for other H. pylori strains.

Lipopolysaccharide, O-antigen, core oligosaccharide, O-specific polysaccharide, Helicobacter pylori

NCBI PubMed ID: 10542057
Journal NLM ID: 0107600
Publisher: Oxford, UK: Blackwell Science Ltd. on behalf of the Federation of European Biochemical Societies
Correspondence: knirel@ioc.ac.ru
Institutions: Clinical Research Centre, Huddinge Hospital, Huddinge, Sweden
Methods: methylation, NMR, ESI-MS

Helicobacter pylori is an important gastroduodenal pathogen of humans whose survival in the gastric environment below pH 4 is dependent on bacterial production of urease, whereas above pH 4 urease-independent mechanisms are involved in survival, but that remain to be elucidated fully. Previous structural investigations on the lipopolysaccharides (LPSs) of H. pylori have shown that the majority of these surface glycolipids express partially fucosylated, glucosylated, or galactosylated N-acetyllactosamine (LacNAc) O-polysaccharide chains containing Lewis(x) (Le(x)) and/or Lewis(y) (Le(y)), although some strains also express type 1 determinants, Lewis(a), Lewis(b), and H-1 antigen. In this study, we investigated acid-induced changes in the structure and composition of LPS and cellular lipids of the genome-sequenced strain, H. pylori 26695. When grown in liquid medium at pH 7, the O-chain consisted of a type 2 LacNAc polysaccharide, which was glycosylated with α-1-fucose at O-3 of the majority of N-acetylglucosamine residues forming Le(x) units, including chain termination by a Le(x) unit. However, growth in liquid medium at pH 5 resulted in production of a more complex O-chain whose backbone of type 2 LacNAc units was partially glycosylated with α-L-fucose, thus forming Le(x), whereas the majority of the nonfucosylated N-acetylglucosamine residues were substituted at O-6 by α-D-galactose residues, and the chain was terminated by a Le(y) unit. In contrast, detailed chemical analysis of the core and lipid A components of LPS and analysis of cellular lipids did not show significant differences between H. pylori 26695 grown at pH 5 and 7. Although putative molecular mechanisms affecting Le(x) and Le(y) expression have been investigated previously, this is the first report identifying an environmental trigger inducing phase variation of Le(x) and Le(y) in H. pylori that can aid adaptation of the bacterium to its ecological niche.

Lipopolysaccharide, structure, Phase variation, phenotype, O-antigen, Helicobacter pylori, Lewis x, blood group antigens, Lewis y

NCBI PubMed ID: 11741906
Publication DOI: 10.1074/jbc.M108574200
Journal NLM ID: 2985121R
Publisher: Baltimore, MD: American Society for Biochemistry and Molecular Biology
Correspondence: pererik.jansson@kfc.hs.sll.se
Institutions: Department of Organic Chemistry, Arrhenius Laboratory, Stockholm University, Stockholm, Sweden, N.D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, Moscow, Russia, Department of Microbiology, National University of Ireland, Galway, Ireland, Karolinska Institute, Clinical Research Centre, Huddinge University Hospital, Huddinge, Sweden
Methods: methylation, NMR, ESI-MS