The MinE ring: an FtsZ-independent cell structure required for selection of the correct division site in E. coli.

E. coli cell division is mediated by the FtsZ ring and associated factors. Selection of the correct division site requires the combined action of an inhibitor of FtsZ ring formation (MinCD) and of a topological specificity factor that somehow prevents MinCD action at the middle of the cell (MinE). Here we show that a biologically active MinE-Gfp fusion accumulates in an annular structure near the middle of young cells. Formation of the MinE ring required MinD but was independent of MinC and continued in nondividing cells in which FtsZ function was inhibited. The results indicate that the MinE ring represents a novel cell structure, which allows FtsZ ring formation at midcell by suppressing MinCD activity at this site.