title: Protein-protein interactions among Helicobacter pylori cag proteins.
abstract: Many Helicobacter pylori isolates contain a 40-kb region of chromosomal DNA known as the cag pathogenicity island (PAI). The risk for development of gastric cancer or peptic ulcer disease is higher among humans infected with cag PAI-positive H. pylori strains than among those infected with cag PAI-negative strains. The cag PAI encodes a type IV secretion system that translocates CagA into gastric epithelial cells. To identify Cag proteins that are expressed by H. pylori during growth in vitro, we compared the proteomes of a wild-type H. pylori strain and an isogenic cag PAI deletion mutant using two-dimensional difference gel electrophoresis (2D-DIGE) in multiple pH ranges. Seven Cag proteins were identified by this approach. We then used a yeast two-hybrid system to detect potential protein-protein interactions among 14 Cag proteins. One heterotypic interaction (CagY/7 with CagX/8) and two homotypic interactions (involving H. pylori VirB11/ATPase and Cag5) were similar to interactions previously reported to occur among homologous components of the Agrobacterium tumefaciens type IV secretion system. Other interactions involved Cag proteins that do not have known homologues in other bacterial species. Biochemical analysis confirmed selected interactions involving five of the proteins that were identified by 2D-DIGE. Protein-protein interactions among Cag proteins are likely to have an important role in the assembly of the H. pylori type IV secretion apparatus.
authors.affiliation: Department of Microbiology and Immunology, Division of Infectious Diseases, A2200 Medical Center North, Vanderbilt University School of Medicine, Nashville, TN 37232, USA.
authors.forename: Valerie J
authors.initials: VJ
authors.lastname: Busler
authors.forename: Victor J
authors.initials: VJ
authors.lastname: Torres
authors.forename: Mark S
authors.initials: MS
authors.lastname: McClain
authors.forename: Oscar
authors.initials: O
authors.lastname: Tirado
authors.forename: David B
authors.initials: DB
authors.lastname: Friedman
authors.forename: Timothy L
authors.initials: TL
authors.lastname: Cover
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism; D000942:Antigens, Bacterial / Q000378:metabolism; D001426:Bacterial Proteins / Q000032:analysis / Q000378:metabolism*; D001692:Biological Transport; D045744:Cell Line, Tumor; D015180:Electrophoresis, Gel, Two-Dimensional; D044404:Genomic Islands / Q000235:genetics; D016481:Helicobacter Infections / Q000378:metabolism / Q000382:microbiology; D016480:Helicobacter pylori / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D006801:Humans; D009154:Mutation; D011485:Protein Binding; D025941:Protein Interaction Mapping; D020543:Proteome / Q000032:analysis / Q000378:metabolism*
chemical_list: D000942:Antigens, Bacterial; D001426:Bacterial Proteins; D020543:Proteome; C080866:cagA protein, Helicobacter pylori; D000251:Adenosine Triphosphatases