title: Insight into the flagella type III export revealed by the complex structure of the type III ATPase and its regulator.
abstract: FliI and FliJ form the FliI6FliJ ATPase complex of the bacterial flagellar export apparatus, a member of the type III secretion system. The FliI6FliJ complex is structurally similar to the α3β3γ complex of F1-ATPase. The FliH homodimer binds to FliI to connect the ATPase complex to the flagellar base, but the details are unknown. Here we report the structure of the homodimer of a C-terminal fragment of FliH (FliHC2) in complex with FliI. FliHC2 shows an unusually asymmetric homodimeric structure that markedly resembles the peripheral stalk of the A/V-type ATPases. The FliHC2-FliI hexamer model reveals that the C-terminal domains of the FliI ATPase face the cell membrane in a way similar to the F/A/V-type ATPases. We discuss the mechanism of flagellar ATPase complex formation and a common origin shared by the type III secretion system and the F/A/V-type ATPases.
authors.affiliation: Department of Macromolecular Science, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043, Japan; kimada@chem.sci.osaka-u.ac.jp.
authors.forename: Katsumi
authors.initials: K
authors.lastname: Imada
authors.affiliation: Graduate School of Frontier Biosciences, Osaka University, Suita, Osaka 565-0871, Japan;
authors.forename: Tohru
authors.initials: T
authors.lastname: Minamino
authors.affiliation: Department of Macromolecular Science, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043, Japan;
authors.forename: Yumiko
authors.initials: Y
authors.lastname: Uchida
authors.affiliation: Department of Macromolecular Science, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043, Japan; Graduate School of Frontier Biosciences, Osaka University, Suita, Osaka 565-0871, Japan;
authors.forename: Miki
authors.initials: M
authors.lastname: Kinoshita
authors.affiliation: Graduate School of Frontier Biosciences, Osaka University, Suita, Osaka 565-0871, Japan; Quantitative Biology Center, RIKEN, Suita, Osaka 565-0871, Japan.
authors.forename: Keiichi
authors.initials: K
authors.lastname: Namba
mesh_terms: D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D005407:Flagella / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D054730:Protein Interaction Domains and Motifs; D055503:Protein Multimerization; D020836:Protein Structure, Quaternary; D006180:Proton-Translocating ATPases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D012486:Salmonella typhimurium / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D055672:Static Electricity; D000069296:Type III Secretion Systems / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D000069296:Type III Secretion Systems; C069250:fliH protein, Bacteria; C069251:fliI protein, bacteria; C069253:fliJ protein, Bacteria; D006180:Proton-Translocating ATPases
keywords: F/A/V-type ATPase; bacterial flagellum; crystal structure; type III protein export