Flagellar motor switch
In molecular biology, the flagellar motor switch is a protein complex. In Escherichia coli and Salmonella typhimurium it regulates the direction of flagellar rotation and hence controls swimming behaviour.[1] The switch is a complex apparatus that responds to signals transduced by the chemotaxis sensory signalling system during chemotactic behaviour.[1] CheY, the chemotaxis response regulator, is believed to act directly on the switch to induce tumbles in the swimming pattern, but no physical interactions of CheY and switch proteins have yet been demonstrated.
| FliG C-terminal domain | |||||||||
|---|---|---|---|---|---|---|---|---|---|
 crystal structure of the middle and c-terminal domains of the flagellar rotor protein flig | |||||||||
| Identifiers | |||||||||
| Symbol | FliG_C | ||||||||
| Pfam | PF01706 | ||||||||
| Pfam clan | CL0436 | ||||||||
| InterPro | IPR000090 | ||||||||
| SCOPe | 1qc7 / SUPFAM | ||||||||
| |||||||||
| Flagellar motor switch protein FliM | |||||||||
|---|---|---|---|---|---|---|---|---|---|
| Identifiers | |||||||||
| Symbol | FliM | ||||||||
| Pfam | PF02154 | ||||||||
| Pfam clan | CL0355 | ||||||||
| InterPro | IPR001689 | ||||||||
| |||||||||
The switch complex comprises at least three proteins - FliG, FliM and FliN. It has been shown that FliG interacts with FliM, FliM interacts with itself, and FliM interacts with FliN.[2] Several amino acids within the middle third of FliG appear to be strongly involved in the FliG-FliM interaction, with residues near the N- or C-termini being less important.[2] Such clustering suggests that FliG-FliM interaction plays a central role in switching.
Analysis of the FliG, FliM and FliN sequences shows that none are especially hydrophobic or appear to be integral membrane proteins.[3] This result is consistent with other evidence suggesting that the proteins may be peripheral to the membrane, possibly mounted on the basal body M ring.[3][4] FliG is present in about 25 copies per flagellum. The structure of the C-terminal domain of FliG is known, this domain functions specifically in motor rotation.[5]
References
- Roman SJ, Frantz BB, Matsumura P (October 1993). "Gene sequence, overproduction, purification and determination of the wild-type level of the Escherichia coli flagellar switch protein FliG". Gene. 133 (1): 103–8. doi:10.1016/0378-1119(93)90232-R. PMID 8224881.
- Marykwas DL, Berg HC (March 1996). "A mutational analysis of the interaction between FliG and FliM, two components of the flagellar motor of Escherichia coli". J. Bacteriol. 178 (5): 1289–94. PMC 177801. PMID 8631704.
- Kihara M, Homma M, Kutsukake K, Macnab RM (June 1989). "Flagellar switch of Salmonella typhimurium: gene sequences and deduced protein sequences". J. Bacteriol. 171 (6): 3247–57. PMC 210043. PMID 2656645.
- Francis NR, Irikura VM, Yamaguchi S, DeRosier DJ, Macnab RM (July 1992). "Localization of the Salmonella typhimurium flagellar switch protein FliG to the cytoplasmic M-ring face of the basal body". Proc. Natl. Acad. Sci. U.S.A. 89 (14): 6304–8. doi:10.1073/pnas.89.14.6304. PMC 49489. PMID 1631122.
- Lloyd SA, Whitby FG, Blair DF, Hill CP (July 1999). "Structure of the C-terminal domain of FliG, a component of the rotor in the bacterial flagellar motor". Nature. 400 (6743): 472–5. doi:10.1038/22794. PMID 10440379.