title: Internal and external components of the bacterial flagellar motor rotate as a unit.
abstract: Most bacteria that swim, including Escherichia coli, are propelled by helical filaments, each driven at its base by a rotary motor powered by a proton or a sodium ion electrochemical gradient. Each motor contains a number of stator complexes, comprising 4MotA 2MotB or 4PomA 2PomB, proteins anchored to the rigid peptidoglycan layer of the cell wall. These proteins exert torque on a rotor that spans the inner membrane. A shaft connected to the rotor passes through the peptidoglycan and the outer membrane through bushings, the P and L rings, connecting to the filament by a flexible coupling known as the hook. Although the external components, the hook and the filament, are known to rotate, having been tethered to glass or marked by latex beads, the rotation of the internal components has remained only a reasonable assumption. Here, by using polarized light to bleach and probe an internal YFP-FliN fusion, we show that the innermost components of the cytoplasmic ring rotate at a rate similar to that of the hook.
authors.affiliation: Rowland Institute at Harvard, Cambridge, MA 02142; Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA 02138.
authors.forename: Basarab G
authors.initials: BG
authors.lastname: Hosu
authors.affiliation: Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA 02138.
authors.forename: Vedavalli S J
authors.initials: VS
authors.lastname: Nathan
authors.affiliation: Rowland Institute at Harvard, Cambridge, MA 02142; Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA 02138 hberg@mcb.harvard.edu.
authors.forename: Howard C
authors.initials: HC
authors.lastname: Berg
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry* / Q000648:ultrastructure*; D008856:Microscopy, Fluorescence / Q000379:methods*; D057054:Molecular Imaging / Q000379:methods*; D020409:Molecular Motor Proteins / Q000737:chemistry* / Q000648:ultrastructure*; D015336:Molecular Probe Techniques; D038761:Photobleaching; D012399:Rotation
chemical_list: D001426:Bacterial Proteins; C077389:FliN protein, Bacteria; D020409:Molecular Motor Proteins
keywords: C ring; Escherichia coli; polarized fluorescence bleaching