title: The Helicobacter pylori anti-sigma factor FlgM is predominantly cytoplasmic and cooperates with the flagellar basal body protein FlhA.
abstract: Helicobacter pylori requires flagellar motility and orientation to persist actively in its habitat. A particular feature of flagella in most Helicobacter species including H. pylori is a membraneous flagellar sheath. The anti-sigma factor FlgM of H. pylori is unusual, since it lacks an N-terminal domain present in other FlgM homologs, e.g., FlgM of Salmonella spp., whose regulatory function is intimately coupled to its secretion through the flagellar type III secretion system. The aim of the present study was to characterize the localization and secretion of the short H. pylori FlgM in the presence of a flagellar sheath and to elucidate its interaction with other flagellar proteins, such as the basal body protein FlhA, which was previously shown to cooperate with FlgM for regulation. H. pylori FlgM was only released into the medium in minor amounts in wild-type bacteria, where the bulk amount of the protein was retained in the cytoplasm. Some FlgM was detected in the flagellar fraction. FlgM was expressed in flhA mutants and was less soluble and differentially localized in bacterial fractions of the flhA mutant in comparison to wild-type bacteria. FlgM-green fluorescent protein and FlgM-V5 translational fusions were generated and expressed in H. pylori. FlgM displayed a predominantly polar distribution and interacted with the C-terminal domain of FlhA (FlhA(C)). We suggest that, in H. pylori, FlgM secretion may not be paramount for its regulatory function and that protein interactions at the flagellar basal body may determine the turnover and localization of functional FlgM.
authors.affiliation: Hannover Medical School, Department for Medical Microbiology and Hospital Epidemiology, Hannover, Germany.
authors.forename: Melanie
authors.initials: M
authors.lastname: Rust
authors.forename: Sophie
authors.initials: S
authors.lastname: Borchert
authors.forename: Eike
authors.initials: E
authors.lastname: Niehus
authors.forename: Sarah A
authors.initials: SA
authors.lastname: Kuehne
authors.forename: Eugenia
authors.initials: E
authors.lastname: Gripp
authors.forename: Afrodita
authors.initials: A
authors.lastname: Bajceta
authors.forename: Jonathan L
authors.initials: JL
authors.lastname: McMurry
authors.forename: Sebastian
authors.initials: S
authors.lastname: Suerbaum
authors.forename: Kelly T
authors.initials: KT
authors.lastname: Hughes
authors.forename: Christine
authors.initials: C
authors.lastname: Josenhans
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D003593:Cytoplasm / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D005407:Flagella / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D005816:Genetic Complementation Test; D016480:Helicobacter pylori / Q000235:genetics / Q000378:metabolism*; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D008854:Microscopy, Electron; D009154:Mutation; D016133:Polymerase Chain Reaction; D011485:Protein Binding; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D020798:Two-Hybrid System Techniques
chemical_list: D001426:Bacterial Proteins; C080688:FlhA protein, Bacteria; D008565:Membrane Proteins; D011994:Recombinant Proteins; C071266:FlgM protein, Bacteria