title: Variable symmetry in Salmonella typhimurium flagellar motors.
abstract: Electron cryomicroscopy of rotor complexes of the Salmonella typhimurium flagellar motor, overproduced in a nonmotile Escherichia coli host, has revealed a variation in subunit symmetry of the cytoplasmic ring (C ring) module. C rings with subunit symmetries ranging from 31 to 38 were found. They formed a Gaussian distribution around a mean between 34 and 35, a similar number to that determined for native C rings. C-ring diameter scaled with the number of subunits, indicating that the elliptical-shaped subunits maintained constant intersubunit spacing. Taken together with evidence that the M ring does not correspondingly increase in size, this finding indicates that rotor assembly does not require strict stoichiometric interactions between the M- and C-ring subunits. Implications for motor function are discussed.
authors.affiliation: Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, New York 13210, USA.
authors.forename: Howard S
authors.initials: HS
authors.lastname: Young
authors.forename: Hongyue
authors.initials: H
authors.lastname: Dang
authors.forename: Yimin
authors.initials: Y
authors.lastname: Lai
authors.forename: David J
authors.initials: DJ
authors.lastname: DeRosier
authors.forename: Shahid
authors.initials: S
authors.lastname: Khan
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000648:ultrastructure; D020285:Cryoelectron Microscopy / Q000379:methods; D004926:Escherichia coli / Q000737:chemistry / Q000235:genetics; D005407:Flagella / Q000737:chemistry* / Q000648:ultrastructure*; D008565:Membrane Proteins / Q000737:chemistry / Q000235:genetics / Q000648:ultrastructure; D020409:Molecular Motor Proteins / Q000737:chemistry* / Q000648:ultrastructure*; D011487:Protein Conformation; D021122:Protein Subunits / Q000737:chemistry; D011994:Recombinant Proteins / Q000737:chemistry / Q000648:ultrastructure; D012486:Salmonella typhimurium / Q000737:chemistry* / Q000648:ultrastructure
chemical_list: D001426:Bacterial Proteins; C077389:FliN protein, Bacteria; C075661:Flif protein, Bacteria; C075660:Flig protein, Bacteria; D008565:Membrane Proteins; D020409:Molecular Motor Proteins; D021122:Protein Subunits; D011994:Recombinant Proteins; C066821:FliM protein, Bacteria