title: Structure of the bacterial flagellar hook and implication for the molecular universal joint mechanism.
abstract: The bacterial flagellum is a motile organelle, and the flagellar hook is a short, highly curved tubular structure that connects the flagellar motor to the long filament acting as a helical propeller. The hook is made of about 120 copies of a single protein, FlgE, and its function as a nano-sized universal joint is essential for dynamic and efficient bacterial motility and taxis. It transmits the motor torque to the helical propeller over a wide range of its orientation for swimming and tumbling. Here we report a partial atomic model of the hook obtained by X-ray crystallography of FlgE31, a major proteolytic fragment of FlgE lacking unfolded terminal regions, and by electron cryomicroscopy and three-dimensional helical image reconstruction of the hook. The model reveals the intricate molecular interactions and a plausible switching mechanism for the hook to be flexible in bending but rigid against twisting for its universal joint function.
authors.affiliation: Dynamic NanoMachine Project, ICORP, JST, 1-3 Yamadaoka, Suita, Osaka 565-0871, Japan.
authors.forename: Fadel A
authors.initials: FA
authors.lastname: Samatey
authors.forename: Hideyuki
authors.initials: H
authors.lastname: Matsunami
authors.forename: Katsumi
authors.initials: K
authors.lastname: Imada
authors.forename: Shigehiro
authors.initials: S
authors.lastname: Nagashima
authors.forename: Tanvir R
authors.initials: TR
authors.lastname: Shaikh
authors.forename: Dennis R
authors.initials: DR
authors.lastname: Thomas
authors.forename: James Z
authors.initials: JZ
authors.lastname: Chen
authors.forename: David J
authors.initials: DJ
authors.lastname: Derosier
authors.forename: Akio
authors.initials: A
authors.lastname: Kitao
authors.forename: Keiichi
authors.initials: K
authors.lastname: Namba
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry* / Q000648:ultrastructure; D003198:Computer Simulation; D020285:Cryoelectron Microscopy; D018360:Crystallography, X-Ray; D008958:Models, Molecular; D010446:Peptide Fragments / Q000737:chemistry / Q000648:ultrastructure; D018583:Pliability; D020836:Protein Structure, Quaternary; D021122:Protein Subunits / Q000737:chemistry; D012486:Salmonella typhimurium / Q000737:chemistry*
chemical_list: D001426:Bacterial Proteins; C097681:FlgE protein, Bacteria; D010446:Peptide Fragments; D021122:Protein Subunits