title: Double hexameric ring assembly of the type III protein translocase ATPase HrcN.
abstract: 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.
authors.affiliation: M. E. Müller Institute for Structural Biology, Biozentrum, University of Basel, Klingelbergstrasse 70, CH-4056 Basel, Switzerland.
authors.forename: Shirley A
authors.initials: SA
authors.lastname: Müller
authors.forename: Charalambos
authors.initials: C
authors.lastname: Pozidis
authors.forename: Remington
authors.initials: R
authors.lastname: Stone
authors.forename: Christian
authors.initials: C
authors.lastname: Meesters
authors.forename: Mohamed
authors.initials: M
authors.lastname: Chami
authors.forename: Andreas
authors.initials: A
authors.lastname: Engel
authors.forename: Anastassios
authors.initials: A
authors.lastname: Economou
authors.forename: Henning
authors.initials: H
authors.lastname: Stahlberg
mesh_terms: D000251:Adenosine Triphosphatases / Q000737:chemistry* / Q000378:metabolism / Q000648:ultrastructure; D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism / Q000648:ultrastructure; D003198:Computer Simulation; D020285:Cryoelectron Microscopy / Q000379:methods; D017348:Microscopy, Electron, Scanning Transmission / Q000379:methods; D008958:Models, Molecular; D008970:Molecular Weight; D020836:Protein Structure, Quaternary; D006180:Proton-Translocating ATPases / Q000737:chemistry / Q000378:metabolism / Q000648:ultrastructure; D044224:Pseudomonas syringae / Q000201:enzymology*; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid
chemical_list: D001426:Bacterial Proteins; D000251:Adenosine Triphosphatases; D006180:Proton-Translocating ATPases