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High Resolution Electron Microscopy of the Helicobacter pylori Cag Type IV Secretion System Pili Produced in Varying Conditions of Iron Availability
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High Resolution Electron Microscopy of the Helicobacter pylori Cag Type IV Secretion System Pili Produced in Varying Conditions of Iron Availability

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Protein-protein interactions among Helicobacter pylori cag proteins

Valerie J Busler1, Victor J Torres, Mark S McClain

  • 1Department of Microbiology and Immunology, Division of Infectious Diseases, A2200 Medical Center North, Vanderbilt University School of Medicine, Nashville, TN 37232, USA.

Journal of Bacteriology
|June 22, 2006
PubMed

Insights

Helicobacter pylori strains with the cag pathogenicity island (PAI) increase gastric cancer risk. Researchers identified seven Cag proteins and mapped their interactions, revealing insights into the type IV secretion system assembly.

Area of Science:

  • Microbiology
  • Molecular Biology
  • Bacterial Pathogenesis

Background:

  • Helicobacter pylori infection is linked to gastric diseases, with cag pathogenicity island (PAI)-positive strains posing a higher risk.
  • The cag PAI encodes a type IV secretion system (T4SS) responsible for translocating bacterial effector proteins like CagA into host cells.
  • Understanding the molecular mechanisms of the H. pylori T4SS is crucial for elucidating its role in pathogenesis.

Purpose of the Study:

  • To identify Cag proteins expressed by H. pylori during in vitro growth.
  • To investigate protein-protein interactions among Cag proteins involved in the T4SS.
  • To elucidate the role of these interactions in the assembly of the H. pylori type IV secretion apparatus.

Main Methods:

  • Comparative proteomic analysis using two-dimensional difference gel electrophoresis (2D-DIGE) of wild-type and cag PAI deletion mutant H. pylori strains.
  • Yeast two-hybrid system to screen for protein-protein interactions among 14 Cag proteins.
  • Biochemical assays to confirm selected protein interactions.

Main Results:

  • Seven Cag proteins were identified through proteomic analysis.
  • Multiple Cag protein-protein interactions were detected, including homotypic and heterotypic interactions.
  • Interactions involving CagY/7 with CagX/8, H. pylori VirB11/ATPase, and Cag5 were characterized, with some showing similarity to Agrobacterium tumefaciens T4SS components.
  • Biochemical validation confirmed interactions for five identified Cag proteins.

Conclusions:

  • The study identified key Cag proteins and their interactions essential for H. pylori T4SS function.
  • These protein-protein interactions are critical for the proper assembly of the type IV secretion apparatus.
  • The findings contribute to understanding the molecular basis of H. pylori pathogenesis and T4SS machinery.

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