title: Function of the conserved FHIPEP domain of the flagellar type III export apparatus, protein FlhA.
abstract: The Type III flagellar protein export apparatus of bacteria consists of five or six membrane proteins, notably FlhA, which controls the export of other proteins and is homologous to the large family of FHIPEP export proteins. FHIPEP proteins contain a highly-conserved cytoplasmic domain. We mutagenized the cloned Salmonella flhA gene for the 692 amino acid FlhA, changing a single, conserved amino acid in the 68-amino acid FHIPEP region. Fifty-two mutations at 30 positions mostly led to loss of motility and total disappearance of microscopically visible flagella, also Western blot protein/protein hybridization showed no detectable export of hook protein and flagellin. There were two exceptions: a D199A mutant strain, which produced short-stubby flagella; and a V151L mutant strain, which did not produce flagella and excreted mainly un-polymerized hook protein. The V151L mutant strain also exported a reduced amount of hook-cap protein FlgD, but when grown with exogenous FlgD it produced polyhooks and polyhook-filaments. A suppressor mutant in the cytoplasmic domain of the export apparatus membrane protein FlhB rescued export of hook-length control protein FliK and facilitated growth of full-length flagella. These results suggested that the FHIPEP region is part of the gate regulating substrate entry into the export apparatus pore.
authors.affiliation: Trans-membrane Trafficking Unit, Okinawa Institute of Science and Technology, Okinawa, Japan.
authors.forename: Clive S
authors.initials: CS
authors.lastname: Barker
authors.affiliation: Trans-membrane Trafficking Unit, Okinawa Institute of Science and Technology, Okinawa, Japan.
authors.forename: Tomoharu
authors.initials: T
authors.lastname: Inoue
authors.affiliation: Trans-membrane Trafficking Unit, Okinawa Institute of Science and Technology, Okinawa, Japan.
authors.forename: Irina V
authors.initials: IV
authors.lastname: Meshcheryakova
authors.affiliation: Trans-membrane Trafficking Unit, Okinawa Institute of Science and Technology, Okinawa, Japan.
authors.forename: Seiya
authors.initials: S
authors.lastname: Kitanobo
authors.affiliation: Trans-membrane Trafficking Unit, Okinawa Institute of Science and Technology, Okinawa, Japan.
authors.forename: Fadel A
authors.initials: FA
authors.lastname: Samatey
mesh_terms: D000595:Amino Acid Sequence; D000596:Amino Acids / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D001692:Biological Transport; D003001:Cloning, Molecular; D003593:Cytoplasm / Q000378:metabolism; D005407:Flagella / Q000378:metabolism*; D005408:Flagellin / Q000378:metabolism; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D009154:Mutation; D000072417:Protein Domains; D012475:Salmonella / Q000235:genetics / Q000378:metabolism; D013379:Substrate Specificity
chemical_list: D000596:Amino Acids; D001426:Bacterial Proteins; C080688:FlhA protein, Bacteria; D008565:Membrane Proteins; D005408:Flagellin