Figure 2.

Dependence of transcription termination on metabolite concentration without feedback. (A) Fraction of terminated RNA transcripts, $f_{ter}$, as a function of the logarithm of the metabolite concentration for different values of $K_2\equiv k_{-f2}/k_{f2}$ with $k_{b2}=k_{b3}=k_b$. Parameters that reproduce the in vitro experimental $f_{ter}$ are listed in Table 1. The inset in (A) shows the half-response metabolite concentration, $T_{50}$, as a function of K₂. (B) Sensitivity of $f_{ter}$ to different values of $k_{b2}$ and $k_{b3}$. Except for modest changes in $T_{50}$ there is little change in $f_{ter}$ when the binding rates are drastically altered. The blue points in (A) and (B) are data from experiments on FMN riboswitch (9).