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Gene Review

flaB  -  flagellin B

Helicobacter pylori J99

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Disease relevance of flaB

  • Sequences of three gene fragments (flaA, flaB, and vacA) from Helicobacter pylori strains isolated from patients in Germany, Canada, and South Africa were analyzed for diversity and for linkage equilibrium by using the Homoplasy Test and compatibility matrices [1].
  • The lpp20 gene encoding this protein was cloned in Escherichia coli by using the vector lambda EMBL3, and plasmid subclones expressed the full-length protein from the native H. pylori promoter. lpp20 was mapped to the same 358-kb NruI fragment as flaB [2].
  • The flagellin proteins in pathogenic bacteria such as Campylobacter jejuni and Helicobacter pylori are heavily glycosylated with the nine-carbon alpha-keto acid, pseudaminic acid [3].
  • Bacterial flagellin, the primary structural component of flagella, is a dominant target of humoral immunity upon infection by enteric pathogens and in Crohn's disease [4].
  • Whereas neither oral nor rectal administration of flagellin elicited a strong serum Ab response, induction of colitis with dextran sodium sulfate resulted in a MyD88-dependent serum Ab response to endogenous flagellin, suggesting that, in an inflammatory milieu, TLR signaling promotes acquisition of Abs to intestinal flagellin [4].

High impact information on flaB


Chemical compound and disease context of flaB

  • A causative agent of gastric and duodenal ulcers, H. pylori, heavily modifies its flagellin with the sialic acid-like sugar 5,7-diacetamido-3,5,7,9-tetradeoxy-l-glycero-alpha-l-manno-nonulosonic acid (pseudaminic acid) [6].

Biological context of flaB

  • As little as 42 bp of DNA upstream of the flaB promoter and 26 bp of DNA sequence downstream of the transcriptional start site were sufficient for efficient FlgR-mediated expression from a flaB'-'xylE reporter gene in H. pylori, indicating that FlgR does not use an enhancer to activate transcription [7].
  • Topoisomerase I of Helicobacter pylori: juxtaposition with a flagellin gene (flaB) and functional requirement of a fourth zinc finger motif [8].
  • Mapping of the transcription start site for the H. pylori flaB gene by a primer extension experiment confirmed the functional activity of the sigma 54 promoter [9].
  • Isogenic flaA and flaB mutants of H. mustelae F1 were constructed by means of reverse genetics [10].
  • Helicobacter pylori possesses two different flagellin genes, flaA and flaB, which are unlinked on the chromosome and transcribed from sigma(28) and sigma(54) promoters, respectively [11].

Anatomical context of flaB

  • In this study we analyzed whether infection with Helicobacter pylori gives rise to specific B-cell responses against a number of putative virulence factors of H. pylori, e.g., urease, flagellin, and different bacterial surface antigens, locally in the gastric mucosa [12].
  • Among these, expression of the genes for the neutrophil activating protein (napA) and the major flagellin subunit (flaA) were significantly induced [13].
  • Salmonella enterica serovar Typhimurium FliC flagellin was able to activate human gastric epithelial cells [14].

Associations of flaB with chemical compounds

  • Isogenic mutant strains of H. mustelae have been constructed by disruption of the flaA or flaB gene with a kanamycin resistance cassette or by introduction of both a kanamycin and a chloramphenicol resistance gene to produce a double mutant [15].
  • The minor 57,000-Mr flagellin species contained a higher content of proline [16].

Other interactions of flaB

  • The double-mutant strain was unable to colonize; the flaA and flaB single-mutant strains were able to initially colonize at a low level and establish persistent infection with increasing numbers of organisms over time [15].
  • In the isogenic mutant of rpoN, transcription of the flaB gene was severely affected, but transcription of the ureA gene (control) was intact [17].

Analytical, diagnostic and therapeutic context of flaB

  • However, Western blot analysis showed substantially reduced amounts of the major flagellin subunit FlaA in the H. pylori 11A ylxH knockout compared to H. pylori 11A [18].
  • A marker strain with wild-type phenotype, carrying multiple plasmid-borne copies of gfp under the control of the H. pylori flaB promoter, was constructed for studies of bacterial distribution and transmission in animal models [19].
  • Sequence alignment of H. pylori flagellin (FlaA) with other bacterial flagellins demonstrates a high degree of similarity in the amino-terminal and carboxy-terminal regions, including those of the closely related genus Campylobacter (56% overall identity with Campylobacter coli flaA), but little homology in the central domain [20].
  • Flagella of Campylobacter pylori were analyzed by electron microscopy and purified, and the molecular weight of the flagellin was determined [21].
  • Using three different reporter genes as well as Northern blot analyses and RT-PCR, it was determined that both flagellin genes are transcribed in a growth phase-dependent fashion [11].


  1. Free recombination within Helicobacter pylori. Suerbaum, S., Smith, J.M., Bapumia, K., Morelli, G., Smith, N.H., Kunstmann, E., Dyrek, I., Achtman, M. Proc. Natl. Acad. Sci. U.S.A. (1998) [Pubmed]
  2. Molecular characterization of a conserved 20-kilodalton membrane-associated lipoprotein antigen of Helicobacter pylori. Kostrzynska, M., O'Toole, P.W., Taylor, D.E., Trust, T.J. J. Bacteriol. (1994) [Pubmed]
  3. PseG of pseudaminic acid biosynthesis: a UDP-sugar hydrolase as a masked glycosyltransferase. Liu, F., Tanner, M.E. J. Biol. Chem. (2006) [Pubmed]
  4. Humoral immune response to flagellin requires T cells and activation of innate immunity. Sanders, C.J., Yu, Y., Moore, D.A., Williams, I.R., Gewirtz, A.T. J. Immunol. (2006) [Pubmed]
  5. Structural, genetic and functional characterization of the flagellin glycosylation process in Helicobacter pylori. Schirm, M., Soo, E.C., Aubry, A.J., Austin, J., Thibault, P., Logan, S.M. Mol. Microbiol. (2003) [Pubmed]
  6. Elucidation of the CMP-pseudaminic acid pathway in Helicobacter pylori: synthesis from UDP-N-acetylglucosamine by a single enzymatic reaction. Schoenhofen, I.C., McNally, D.J., Brisson, J.R., Logan, S.M. Glycobiology (2006) [Pubmed]
  7. Helicobacter pylori FlgR is an enhancer-independent activator of sigma54-RNA polymerase holoenzyme. Brahmachary, P., Dashti, M.G., Olson, J.W., Hoover, T.R. J. Bacteriol. (2004) [Pubmed]
  8. Topoisomerase I of Helicobacter pylori: juxtaposition with a flagellin gene (flaB) and functional requirement of a fourth zinc finger motif. Suerbaum, S., Brauer-Steppkes, T., Labigne, A., Cameron, B., Drlica, K. Gene (1998) [Pubmed]
  9. Cloning and genetic characterization of the Helicobacter pylori and Helicobacter mustelae flaB flagellin genes and construction of H. pylori flaA- and flaB-negative mutants by electroporation-mediated allelic exchange. Suerbaum, S., Josenhans, C., Labigne, A. J. Bacteriol. (1993) [Pubmed]
  10. Comparative ultrastructural and functional studies of Helicobacter pylori and Helicobacter mustelae flagellin mutants: both flagellin subunits, FlaA and FlaB, are necessary for full motility in Helicobacter species. Josenhans, C., Labigne, A., Suerbaum, S. J. Bacteriol. (1995) [Pubmed]
  11. Growth phase-dependent and differential transcriptional control of flagellar genes in Helicobacter pylori. Niehus, E., Ye, F., Suerbaum, S., Josenhans, C. Microbiology (Reading, Engl.) (2002) [Pubmed]
  12. Antibody-secreting cells in the stomachs of symptomatic and asymptomatic Helicobacter pylori-infected subjects. Mattsson, A., Quiding-Järbrink, M., Lönroth, H., Hamlet, A., Ahlstedt, I., Svennerholm, A. Infect. Immun. (1998) [Pubmed]
  13. Gene expression profiling of Helicobacter pylori reveals a growth-phase-dependent switch in virulence gene expression. Thompson, L.J., Merrell, D.S., Neilan, B.A., Mitchell, H., Lee, A., Falkow, S. Infect. Immun. (2003) [Pubmed]
  14. Helicobacter pylori flagellins have very low intrinsic activity to stimulate human gastric epithelial cells via TLR5. Lee, S.K., Stack, A., Katzowitsch, E., Aizawa, S.I., Suerbaum, S., Josenhans, C. Microbes Infect. (2003) [Pubmed]
  15. Infection of the ferret stomach by isogenic flagellar mutant strains of Helicobacter mustelae. Andrutis, K.A., Fox, J.G., Schauer, D.B., Marini, R.P., Li, X., Yan, L., Josenhans, C., Suerbaum, S. Infect. Immun. (1997) [Pubmed]
  16. Identification, characterization, and spatial localization of two flagellin species in Helicobacter pylori flagella. Kostrzynska, M., Betts, J.D., Austin, J.W., Trust, T.J. J. Bacteriol. (1991) [Pubmed]
  17. Allelic exchange mutagenesis of rpoN encoding RNA-polymerase sigma54 subunit in Helicobacter pylori. Fujinaga, R., Nakazawa, T., Shirai, M. J. Infect. Chemother. (2001) [Pubmed]
  18. Helicobacter pylori HP1034 (ylxH) is required for motility. van Amsterdam, K., van der Ende, A. Helicobacter (2004) [Pubmed]
  19. Green fluorescent protein as a novel marker and reporter system in Helicobacter sp. Josenhans, C., Friedrich, S., Suerbaum, S. FEMS Microbiol. Lett. (1998) [Pubmed]
  20. Cloning and genetic characterization of a Helicobacter pylori flagellin gene. Leying, H., Suerbaum, S., Geis, G., Haas, R. Mol. Microbiol. (1992) [Pubmed]
  21. Ultrastructure and chemical analysis of Campylobacter pylori flagella. Geis, G., Leying, H., Suerbaum, S., Mai, U., Opferkuch, W. J. Clin. Microbiol. (1989) [Pubmed]
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