title: Characterization of the pilin ortholog of the Helicobacter pylori type IV cag pathogenicity apparatus, a surface-associated protein expressed during infection.
abstract: The Helicobacter pylori cag pathogenicity island (cag PAI) encodes components of a type IV secretion system (T4SS) involved in host interaction and pathogenicity. Previously, seven cag PAI proteins were identified as homologs of Agrobacterium tumefaciens Vir proteins, which form a paradigm T4SS. The T pilus composed of the processed VirB2 pilin is an external structural part of the A. tumefaciens T4SS. In H. pylori, cag-dependent assembly of pili has not been observed so far, nor has a pilin (VirB2) ortholog been characterized. We have here identified, using a motif-based search, an H. pylori cag island protein (HP0546) that possesses sequence and predicted structural similarities to VirB2-like pilins of other T4SSs. The HP0546 protein displays interstrain variability in its terminal domains. HP0546 was expressed as a FLAG-tagged fusion protein in Escherichia coli, A. tumefaciens, and H. pylori and was detected as either two or three bands of different molecular masses in the insoluble fraction, indicating protein processing. As reported previously, isogenic H. pylori mutants in the putative cag pilin gene had reduced abilities to induce cag PAI-dependent interleukin-8 secretion in gastric epithelial cells. Fractionation analysis of H. pylori, using a specific antiserum raised against an N-terminal HP0546 peptide, showed that the protein is partially surface exposed and that its surface localization depended upon an intact cag system. By immunoelectron microscopy, HP0546 was localized in surface appendages, with surface exposure of an N-terminal epitope. Pronounced strain-to-strain variability of this predicted surface-exposed part of HP0546 indicates a strong selective pressure for variation in vivo.
authors.affiliation: Hannover Medical School, Institute for Medical Microbiology, Carl-Neuberg-Strasse 1, Hannover 30625, Germany.
authors.forename: Joanna
authors.initials: J
authors.lastname: Andrzejewska
authors.forename: Sae Kyung
authors.initials: SK
authors.lastname: Lee
authors.forename: Patrick
authors.initials: P
authors.lastname: Olbermann
authors.forename: Nina
authors.initials: N
authors.lastname: Lotzing
authors.forename: Elena
authors.initials: E
authors.lastname: Katzowitsch
authors.forename: Bodo
authors.initials: B
authors.lastname: Linz
authors.forename: Mark
authors.initials: M
authors.lastname: Achtman
authors.forename: Clarence I
authors.initials: CI
authors.lastname: Kado
authors.forename: Sebastian
authors.initials: S
authors.lastname: Suerbaum
authors.forename: Christine
authors.initials: C
authors.lastname: Josenhans
mesh_terms: D000595:Amino Acid Sequence; D000942:Antigens, Bacterial / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D045744:Cell Line, Tumor; D004847:Epithelial Cells / Q000378:metabolism / Q000382:microbiology; D036781:Fimbriae Proteins / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D016481:Helicobacter Infections / Q000382:microbiology*; D016480:Helicobacter pylori / Q000166:cytology / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D008565:Membrane Proteins / Q000378:metabolism; D008969:Molecular Sequence Data; D021122:Protein Subunits
chemical_list: D000942:Antigens, Bacterial; D001426:Bacterial Proteins; D008565:Membrane Proteins; D021122:Protein Subunits; C080866:cagA protein, Helicobacter pylori; D036781:Fimbriae Proteins