Positive Gene Regulation? Activator?

- Some operons are also subject to positive control through a stimulatory protein, called an activator of transcription​ - When glucose (a preferred food source of E. coli) is scarce, a specific activator attaches to the promoter of the lac operon and increases the affinity of RNA polymerase, thus accelerating transcription​ - When glucose levels increase, the activator detaches from the lac operon, and transcription returns to a normal, low level​ - The ability to catalyze compounds like lactose enables cells deprived of glucose to survive​