title: Systematic site-directed mutagenesis of the Helicobacter pylori CagL protein of the Cag type IV secretion system identifies novel functional domains.
abstract: The Cag Type IV secretion system, which contributes to inflammation and cancerogenesis during chronic infection, is one of the major virulence factors of the bacterial gastric pathogen Helicobacter pylori. We have generated and characterized a series of non-marked site-directed chromosomal mutants in H. pylori to define domains of unknown function of the essential tip protein CagL of the Cag secretion system. Characterizing the CagL mutants, we determined that their function to activate cells and transport the effector CagA was reduced to different extents. We identified three novel regions of the CagL protein, involved in its structural integrity, its possible interaction with the CagPAI T4SS pilus protein CagI, and in its binding to integrins and other host cell ligands. In particular two novel variable CagL motifs were involved in integrin binding, TSPSA, and TASLI, which is located opposite of its integrin binding motif RGD. We thereby defined functionally important subdomains within the CagL structure, which can be used to clarify CagL contributions in the context of other CagPAI proteins or for inhibition of the CagT4SS. This structure-function correlation of CagL domains can also be instructive for the functional characterization of other potential VirB5 orthologs whose structure is not yet known.
authors.affiliation: Medizinische Hochschule Hannover, Institute for Medical Microbiology, Carl-Neuberg-Strasse 1, 30625 Hannover, Germany.|DZIF German Center for Infection Research, partner site Hannover-Braunschweig, Carl Neuberg Str 1, 30625 Hannover, Germany.
authors.forename: Tobias
authors.initials: T
authors.lastname: Bönig
authors.affiliation: Medizinische Hochschule Hannover, Institute for Medical Microbiology, Carl-Neuberg-Strasse 1, 30625 Hannover, Germany.|DZIF German Center for Infection Research, partner site Hannover-Braunschweig, Carl Neuberg Str 1, 30625 Hannover, Germany.
authors.forename: Patrick
authors.initials: P
authors.lastname: Olbermann
authors.affiliation: Medizinische Hochschule Hannover, Institute for Medical Microbiology, Carl-Neuberg-Strasse 1, 30625 Hannover, Germany.|DZIF German Center for Infection Research, partner site Hannover-Braunschweig, Carl Neuberg Str 1, 30625 Hannover, Germany.
authors.forename: Simon H
authors.initials: SH
authors.lastname: Bats
authors.affiliation: Ludwig Maximilians University Munich, Max-von-Pettenkofer Institute, Munich, Germany.|DZIF German Center for Infection Research, partner site Munich, Pettenkoferstr. 9, 80336 Munich, Germany.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Fischer
authors.affiliation: Medizinische Hochschule Hannover, Institute for Medical Microbiology, Carl-Neuberg-Strasse 1, 30625 Hannover, Germany.|DZIF German Center for Infection Research, partner site Hannover-Braunschweig, Carl Neuberg Str 1, 30625 Hannover, Germany.
authors.forename: Christine
authors.initials: C
authors.lastname: Josenhans
mesh_terms: D000942:Antigens, Bacterial / Q000235:genetics; D001426:Bacterial Proteins / Q000235:genetics*; D045744:Cell Line, Tumor; D016481:Helicobacter Infections / Q000382:microbiology; D016480:Helicobacter pylori / Q000235:genetics*; D054884:Host-Pathogen Interactions / Q000235:genetics; D006801:Humans; D016023:Integrins / Q000235:genetics; D016297:Mutagenesis, Site-Directed / Q000379:methods; D011485:Protein Binding / Q000235:genetics; D021381:Protein Transport / Q000235:genetics; D013270:Stomach / Q000382:microbiology; D000069319:Type IV Secretion Systems / Q000235:genetics*
chemical_list: D000942:Antigens, Bacterial; D001426:Bacterial Proteins; D016023:Integrins; D000069319:Type IV Secretion Systems; C568315:cagL protein, Helicobacter pylori