Interacting components of the flagellar motor of Escherichia coli revealed by the two-hybrid system in yeast.

The ability of the flagellar motor of Escherichia coli to switch between clockwise and counterclockwise modes of operation is ultimately responsible for the swimming behavior of the cell. Three motor proteins, FliG, FliM, and FliN, have been implicated in this process. Using the two-hybrid system in Saccharomyces cerevisiae, we demonstrated strong interactions between FliG/FliM,FliM/FliM, and FliM/FliN. A screen for other components that might interact with FliG revealed interactions with FliF (the MS ring protein) and H-NS (a histone-like protein). Regions of proteins important for several of these interactions were identified by mutational analysis. The implications for motor assembly and function are discussed.