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Overproduced Salmonella typhimurium flagellar motor switch complexes.
1Laboratory of Cellular Bioenergetics, Department of Physiology and Biophysics, Albert Einstein College of Medicine, Bronx, NY 10461, USA.
Journal of Molecular Biology
|May 2, 2000
Summary
Salmonella typhimurium flagellar motor proteins FliG, FliM, and FliN assemble into the C-ring structure. This assembly occurs independently of other flagellar components, confirming their role in motor function.
Area of Science:
- Microbiology
- Molecular Biology
- Structural Biology
Background:
- The flagellar motor of Salmonella typhimurium controls bacterial motility through rotation.
- Specific proteins, FliG, FliM, and FliN, are crucial for regulating the direction of flagellar rotation.
- These proteins are known to localize to the cytoplasmic C-ring of the flagellar base.
Purpose of the Study:
- To investigate the in vivo assembly and localization of Salmonella typhimurium flagellar motor proteins FliG, FliM, and FliN.
- To determine if these proteins alone can form morphologically correct C-ring structures.
- To confirm the role of the C-ring as a dedicated motor component and its assembly process.
Main Methods:
- Plasmid-encoded expression of FliG, FliM, FliN, and FliF in Escherichia coli.
- Immuno-electron microscopy for protein localization and structure determination.
- Morphological analysis of assembled structures.
Main Results:
- Morphologically intact structures resembling native MS-ring and C-ring basal body modules were formed.
- These structures localized to the cell membrane and contained FliG, FliM, and FliN.
- The C-ring assembly onto the MS-ring proceeded correctly without other flagellar components.
Conclusions:
- The C-ring of the Salmonella flagellar motor is composed solely of FliG, FliM, and FliN.
- These proteins function as a dedicated component of the motor.
- Proper C-ring assembly on the MS-ring is independent of other flagellar structural elements.