Insight into the flagella type III export revealed by the complex structure of the type III ATPase and its regulator

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 113; no. 13; pp. 3633 - 3638
• Main Authors: Imada, Katsumi, Minamino, Tohru, Uchida, Yumiko, Kinoshita, Miki, Namba, Keiichi
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 29.03.2016; National Acad Sciences
• Subjects: Adenosine triphosphatase; Amino Acid Sequence; Amino Acid Substitution; Bacterial Proteins - chemistry; Bacterial Proteins - genetics; Bacterial Proteins - metabolism; Biological Sciences; Cells; Flagella - chemistry; Flagella - genetics; Flagella - metabolism; Membranes; Models, Molecular; Molecular Sequence Data; Mutagenesis, Site-Directed; Protein Interaction Domains and Motifs; Protein Multimerization; Protein Structure, Quaternary; Proton-Translocating ATPases - chemistry; Proton-Translocating ATPases - genetics; Proton-Translocating ATPases - metabolism; Salmonella typhimurium - genetics; Salmonella typhimurium - metabolism; Sequence Homology, Amino Acid; Static Electricity; Type III Secretion Systems - chemistry; Type III Secretion Systems - genetics; Type III Secretion Systems - metabolism; crystal structure; bacterial flagellum; type III protein export; F/A/V-type ATPase
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.1524025113

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.