Double hexameric ring assembly of the type III protein translocase ATPase HrcN

Mol Microbiol. 2006 Jul;61(1):119-25. doi: 10.1111/j.1365-2958.2006.05219.x.


The specialized type III secretion (T3S) apparatus of pathogenic and symbiotic Gram-negative bacteria comprises a complex transmembrane organelle and an ATPase homologous to the F1-ATPase beta subunit. The T3S ATPase HrcN of Pseudomonas syringae associates with the inner membrane, and its ATP hydrolytic activity is stimulated by dodecamerization. The structure of dodecameric HrcN (HrcN12) determined to 1.6 nm by cryo-electron microscopy is presented. HrcN12 comprises two hexameric rings that are probably stacked face-to-face by the association of their C-terminal domains. It is 11.5 +/- 1.0 nm in diameter, 12.0 +/- 2.0 nm high and has a 2.0-3.8 nm wide inner channel. This structure is compared to a homology model based on the structure of the F1-beta-ATPase. A model for its incorporation within the T3S apparatus is presented.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenosine Triphosphatases / chemistry*
  • Adenosine Triphosphatases / metabolism
  • Adenosine Triphosphatases / ultrastructure
  • Bacterial Proteins / chemistry*
  • Bacterial Proteins / metabolism
  • Bacterial Proteins / ultrastructure
  • Computer Simulation
  • Cryoelectron Microscopy / methods
  • Microscopy, Electron, Scanning Transmission / methods
  • Models, Molecular
  • Molecular Weight
  • Protein Structure, Quaternary
  • Proton-Translocating ATPases / chemistry
  • Proton-Translocating ATPases / metabolism
  • Proton-Translocating ATPases / ultrastructure
  • Pseudomonas syringae / enzymology*
  • Sequence Alignment
  • Sequence Homology, Amino Acid


  • Bacterial Proteins
  • Adenosine Triphosphatases
  • Proton-Translocating ATPases