title: Molecular basis of the interaction between the flagellar export proteins FliI and FliH from Helicobacter pylori.
abstract: Bacterial flagellar protein export requires an ATPase, FliI, and presumptive inhibitor, FliH. We have explored the molecular basis for FliI/FliH interaction in the human gastric pathogen Helicobacter pylori. By using bioinformatic and biochemical analyses, we showed that residues 1-18 of FliI very likely form an amphipathic alpha-helix upon interaction with FliH, and that residues 21-91 of FliI resemble the N-terminal oligomerization domain of the F1-ATPase catalytic subunits. A truncated FliI-(2-91) protein was shown to be folded, although the N-terminal 18 residues were likely unstructured. Deletion and scanning mutagenesis showed that residues 1-18 of FliI were essential for the FliI/FliH interaction. Scanning mutation of amino acids in the N-terminal 10 residues of FliI indicated that a cluster of hydrophobic residues in this segment was critical for the interaction with FliH. The interaction between FliI and FliH has similarities to the interaction between the N-terminal alpha-helix of the F1-ATPase alpha-subunit and the globular domain of the F1-ATPase delta-subunit, respectively. This similarity suggests that FliH may function as a molecular stator.
authors.affiliation: Department of Biochemistry, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5E5, Canada.
authors.forename: Michael C
authors.initials: MC
authors.lastname: Lane
authors.forename: Paul W
authors.initials: PW
authors.lastname: O'Toole
authors.forename: Stanley A
authors.initials: SA
authors.lastname: Moore
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D002942:Circular Dichroism; D005407:Flagella / Q000378:metabolism*; D016480:Helicobacter pylori / Q000378:metabolism*; D008565:Membrane Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D016296:Mutagenesis; D017510:Protein Folding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D006180:Proton-Translocating ATPases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D012486:Salmonella typhimurium / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; D008565:Membrane Proteins; D011994:Recombinant Proteins; C069250:fliH protein, Bacteria; C074426:FliL protein, Bacteria; D006180:Proton-Translocating ATPases