xlnR promoter region activity Plot of the xlnR promoter region activities defined by ΓA, ΓR and ΓAΓR depending on the regulator. The term ΓAΓR - is the combined affect of competitive binding to promoter region by activators and repressors. Plots (A) and (B) show the influence of weak (k
= 1) and strong (k
= 5) synthesis parameters respectively.