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Molecular cloning and characterization of the Helicobacter pylori fliD gene, an essential factor in flagellar structure and motility.

ABSTRACT: Helicobacter pylori colonizes the human stomach and can cause gastroduodenal disease. Flagellar motility is regarded as a major factor in the colonizing ability of H. pylori. The functional roles of flagellar structural proteins other than FlaA, FlaB, and FlgE are not well understood. The fliD operon of H. pylori consists of flaG, fliD, and fliS genes, in the order stated, under the control of a sigma(28)-dependent promoter. In an effort to elucidate the function of the FliD protein, a hook-associated protein 2 homologue, in flagellar morphogenesis and motility, the fliD gene (2,058 bp) was cloned and isogenic mutants were constructed by disruption of the fliD gene with a kanamycin resistance cassette and electroporation-mediated allelic-exchange mutagenesis. In the fliD mutant, morphologically abnormal flagellar appendages in which very little filament elongation was apparent were observed. The fliD mutant strain was completely nonmotile, indicating that these abnormal flagella were functionally defective. Furthermore, the isogenic fliD mutant of H. pylori SS1, a mouse-adapted strain, was not able to colonize the gastric mucosae of host mice. These results suggest that H. pylori FliD is an essential element in the assembly of the functional flagella that are required for colonization of the gastric mucosa.

SUBMITTER: Kim JS

PROVIDER: S-EPMC94171 | biostudies-literature | 1999 Nov

REPOSITORIES: biostudies-literature

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Molecular cloning and characterization of the Helicobacter pylori fliD gene, an essential factor in flagellar structure and motility.

Kim J S JS Chang J H JH Chung S I SI Yum J S JS

Journal of bacteriology 19991101 22

Helicobacter pylori colonizes the human stomach and can cause gastroduodenal disease. Flagellar motility is regarded as a major factor in the colonizing ability of H. pylori. The functional roles of flagellar structural proteins other than FlaA, FlaB, and FlgE are not well understood. The fliD operon of H. pylori consists of flaG, fliD, and fliS genes, in the order stated, under the control of a sigma(28)-dependent promoter. In an effort to elucidate the function of the FliD protein, a hook-asso ...[more]

PMID: 10559162

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Project description:UnlabelledHelicobacter pylori contains four genes that are predicted to encode proteins secreted by the autotransporter (type V) pathway. One of these, the pore-forming toxin VacA, has been studied in great detail, but thus far there has been very little investigation of three VacA-like proteins. We show here that all three VacA-like proteins are >250 kDa in mass and localized on the surface of H. pylori. The expression of the three vacA-like genes is upregulated during H. pylori colonization of the mouse stomach compared to H. pylori growth in vitro, and a wild-type H. pylori strain outcompeted each of the three corresponding isogenic mutant strains in its ability to colonize the mouse stomach. One of the VacA-like proteins localizes to a sheath that overlies the flagellar filament and bulb, and therefore, we designate it FaaA (flagella-associated autotransporter A). In comparison to a wild-type H. pylori strain, an isogenic faaA mutant strain exhibits decreased motility, decreased flagellar stability, and an increased proportion of flagella in a nonpolar site. The flagellar localization of FaaA differs markedly from the localization of other known autotransporters, and the current results reveal an important role of FaaA in flagellar localization and motility.ImportanceThe pathogenesis of most bacterial infections is dependent on the actions of secreted proteins, and proteins secreted by the autotransporter pathway constitute the largest family of secreted proteins in pathogenic Gram-negative bacteria. In this study, we analyzed three autotransporter proteins (VacA-like proteins) produced by Helicobacter pylori, a Gram-negative bacterium that colonizes the human stomach and contributes to the pathogenesis of gastric cancer and peptic ulcer disease. We demonstrate that these three proteins each enhance the capacity of H. pylori to colonize the stomach. Unexpectedly, one of these proteins (FaaA) is localized to a sheath that overlies H. pylori flagella. The absence of FaaA results in decreased H. pylori motility as well as a reduction in flagellar stability and a change in flagellar localization. The atypical localization of FaaA reflects a specialized function of this autotransporter designed to optimize H. pylori colonization of the gastric niche.

Dataset Information

Molecular cloning and characterization of the Helicobacter pylori fliD gene, an essential factor in flagellar structure and motility.

Publications

Molecular cloning and characterization of the Helicobacter pylori fliD gene, an essential factor in flagellar structure and motility.

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