title: The FliN-FliH interaction mediates localization of flagellar export ATPase FliI to the C ring complex.
abstract: FliH regulates the flagellar export ATPase FliI, preventing nonproductive ATP hydrolysis. FliH has been shown to stably associate with the C ring protein FliN. Analysis of this complex reveals that FliH is required for FliI localization to the C ring, and thus FliH not only inhibits FliI ATPase activity but also may act to target FliI to the basal body. Quantitative binding studies revealed a KD of 110 nM for FliH binding to FliN. The KD for FliH binding of a FliN variant from a temperature-sensitive nonflagellate fliN point mutant was determined to be 270 nM, suggesting a molecular explanation for its phenotype. Another variant FliN from a temperature-sensitive mutant with a different phenotype displayed binding with an intermediate affinity. Weak export activity in a fliN null mutant was greatly increased by overproduction of FliI, mimicking a previously observed FliH bypass effect and supporting the conclusion that FliN-FliH binding is important for localization of FliI to the C ring and thus the membrane-embedded export apparatus beyond. A model incorporating the present findings is presented.
authors.affiliation: Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut 06520-8114, USA. jmcmurr1@kennesaw.edu
authors.forename: Jonathan L
authors.initials: JL
authors.lastname: McMurry
authors.forename: James W
authors.initials: JW
authors.lastname: Murphy
authors.forename: Bertha
authors.initials: B
authors.lastname: González-Pedrajo
mesh_terms: D000255:Adenosine Triphosphate / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002462:Cell Membrane / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D005407:Flagella / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D006358:Hot Temperature; D046912:Multiprotein Complexes / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D009154:Mutation; D011485:Protein Binding; D017434:Protein Structure, Tertiary / Q000235:genetics; D021381:Protein Transport / Q000235:genetics; D006180:Proton-Translocating ATPases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D019779:Salmonella enterica / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D046912:Multiprotein Complexes; C069250:fliH protein, Bacteria; C069251:fliI protein, bacteria; D000255:Adenosine Triphosphate; D006180:Proton-Translocating ATPases