This Article Full Text (PDF) Other Versions of this Article: JB.01281-06v1 189/2/305    most recent Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Reprints and Permissions Copyright Information Books from ASM Press MicrobeWorld Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Brown, P. N. Articles by Blair, D. F. Search for Related Content PubMed PubMed Citation Articles by Brown, P. N. Articles by Blair, D. F.

 Previous Article  |  Next Article 

J. Bacteriol. doi:10.1128/JB.01281-06
Copyright (c) 2006, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.

Mutational Analysis of the Flagellar Protein FliG: Sites of Interaction with FliM and Implications for Organization of the Switch Complex

Department of Biology, University of Utah, 257 S 1400 East, Salt Lake City, UT 84112-0840

^* To whom correspondence should be addressed. Email: blair{at}bioscience.utah.edu.

	Abstract

The switch complex at the base of the bacterial flagellum is essential for flagellar assembly, rotation, and switching. In E. coli and Salmonella, the complex contains about 26 copies of FliG, 34 copies of FliM, and more then 100 copies of FliN, together forming the basal body C-ring. FliG is involved most directly in motor rotation and is located in the upper (membrane-proximal) part of the C-ring. A crystal structure of the middle and C-terminal parts of FliG shows two globular domains connected by an -helix and a short extended segment. The middle domain of FliG has a conserved surface patch formed by the residues EHPQ_125-128 and R₁₆₀ (the EHPQR motif), and the C-terminal domain has a conserved surface hydrophobic patch. To examine the functional importance of these and other surface features of FliG, we made mutations in residues distributed over the protein surface and measured the effects on flagellar assembly and function. Mutations preventing flagellar assembly occurred mainly in the vicinity of the EHPQR motif and the hydrophobic patch. Mutations causing aberrant CW or CCW motor bias occurred in these same regions, and in the waist between the upper and lower parts of the C-terminal domain. Pulldown assays with GST-FliM showed that FliG interacts with FliM through both the EHPQR motif and the hydrophobic patch. We propose a model for the organization of FliG and FliM subunits that accounts for the FliG-FliM interactions identified here and for the different copy numbers of FliG and FliM in the flagellum.

This article has been cited by other articles:

• Tu, Y. (2008). The nonequilibrium mechanism for ultrasensitivity in a biological switch: Sensing by Maxwell's demons. Proc. Natl. Acad. Sci. USA 105: 11737-11741 [Abstract] [Full Text]  
• Blair, K. M., Turner, L., Winkelman, J. T., Berg, H. C., Kearns, D. B. (2008). A Molecular Clutch Disables Flagella in the Bacillus subtilis Biofilm. Science 320: 1636-1638 [Abstract] [Full Text]  
• Passmore, S. E., Meas, R., Marykwas, D. L. (2008). Analysis of the FliM/FliG motor protein interaction by two-hybrid mutation suppression analysis. Microbiology 154: 714-724 [Abstract] [Full Text]  
• Mashimo, T., Hashimoto, M., Yamaguchi, S., Aizawa, S.-I. (2007). Temperature-Hypersensitive Sites of the Flagellar Switch Component FliG in Salmonella enterica Serovar Typhimurium. J. Bacteriol. 189: 5153-5160 [Abstract] [Full Text]  
• Manson, M. D. (2007). How 34 Pegs Fit into 26 + 8 Holes in the Flagellar Motor. J. Bacteriol. 189: 291-293 [Full Text]