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

Proc Natl Acad Sci U S A. 2016 Mar 29;113(13):3633-8. doi: 10.1073/pnas.1524025113. Epub 2016 Mar 16.

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.

Keywords: F/A/V-type ATPase; bacterial flagellum; crystal structure; type III protein export.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Amino Acid Substitution
  • Bacterial Proteins / chemistry*
  • Bacterial Proteins / genetics
  • Bacterial Proteins / metabolism
  • Flagella / chemistry
  • Flagella / genetics
  • Flagella / metabolism
  • 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

Substances

  • Bacterial Proteins
  • Type III Secretion Systems
  • fliH protein, Bacteria
  • fliI protein, bacteria
  • fliJ protein, Bacteria
  • Proton-Translocating ATPases

Associated data

  • PDB/5B0O