In molecular biology, the flagellar motor switch protein(Flig) is one of three proteins in certain bacteria coded for by the gene fliG.[1] The other two proteins are FliN coded for by fliN,[2] and FliM coded for by fliM.[3] The protein complex regulates the direction of flagellar rotation and hence controls swimming behaviour.[4] The switch is a complex apparatus that responds to signals transduced by the chemotaxis sensory signalling system during chemotactic behaviour.[4] CheY, the chemotaxis response regulator, is believed to act directly on the switch to induce a switch in the flagellar motor direction of rotation.
The switch complex comprises at least three proteins - FliG, FliM and FliN.[2] It has been shown that FliG interacts with FliM, FliM interacts with itself, and FliM interacts with FliN.[5] Several amino acids within the middle third of FliG appear to be strongly involved in the FliG-FliM interaction, with residues near the N-orC-termini being less important.[5] 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.[6] 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.[6][7] 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.[8]
^ abRoman 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. PMID8224881.
