FIG. 5.

Model depicting the coordinate regulation of LEE and flagellar gene expressions by the GrlR-GrlA system in EHEC. GrlA activates LEE expression via activation of ler transcription, whereas it inhibits transcription of the flhD operon in response to GrlR levels in the cell. ClpXP positively regulates LEE expression by controlling changes in GrlR and RpoS levels and directly or indirectly represses the flagellar regulon by altering the stabilities of FlhD/FlhC and GrlR. As described in the text, additional regulatory elements, such as Fis, H-NS, IHF, Hha, GadX, YhiE, YhiF, BipA, EtrA, EivF, GrvA, and quorum sensing, have also been implicated in the regulation of LEE.