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Variable Symmetry in Salmonella typhimurium Flagellar Motors

Authors
  • Howard S. Young
  • Hongyue Dang
  • Yimin Lai
  • David J. DeRosier
  • Shahid Khan
Publisher
Biophysical Society
Publication Date
Jan 01, 2003
Source
PMC
Keywords
License
Unknown

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.

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