Fig. 1. Components of the Q regulatory system.
(A) The transcription factor QF activates QUAS-regulated genes to produce reporter or effector proteins (indicated by X). (B) QF activity is blocked by the repressor QS. (C) QS repression of the QF/QUAS interaction is alleviated by addition of quinic acid (QA). P1 and P2 represent promoter/enhancer sequences for QF and QS transcription.