Fig. 5.

Summary model. The population of open (activated) rpoS leader in the presence of sRNAs was simulated from the in vitro binding data [Table 1, (23)]: DsrA at 37 °C (dark blue), DsrA at 25 °C (light blue), and ArcZ (brown). Solid curves, no Hfq; dashed curves, with Hfq. Vertical dashed lines show the expected fraction of translatable rpoS leader when sRNAs are present at either endogenous or overexpressed levels. (Top) sRNA activation of the WT rpoS leader; (Bottom) sRNA activation of the (AAN)₄ mutant rpoS leader. It was assumed that the mutation does not affect sRNA binding, and that the presence of Hfq improves sRNA binding to the mutant by ∼1.5-fold, similar to the kinetic behavior reported in ref. 23.