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.
Publication types
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Bacterial Proteins / chemistry
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Bacterial Proteins / genetics
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Bacterial Proteins / ultrastructure
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Cryoelectron Microscopy / methods
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Escherichia coli / chemistry
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Escherichia coli / genetics
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Flagella / chemistry*
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Flagella / ultrastructure*
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Membrane Proteins / chemistry
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Membrane Proteins / genetics
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Membrane Proteins / ultrastructure
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Molecular Motor Proteins / chemistry*
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Molecular Motor Proteins / ultrastructure*
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Protein Conformation
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Protein Subunits / chemistry
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Recombinant Proteins / chemistry
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Recombinant Proteins / ultrastructure
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Salmonella typhimurium / chemistry*
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Salmonella typhimurium / ultrastructure
Substances
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Bacterial Proteins
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FliN protein, Bacteria
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Flif protein, Bacteria
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Flig protein, Bacteria
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Membrane Proteins
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Molecular Motor Proteins
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Protein Subunits
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Recombinant Proteins
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FliM protein, Bacteria