Figure 4: Extent of operon coupling predicted by the sliding RNAP model, using the kinetic parameter values from Table 2.

a. Distribution of search times that end in a promoter encounter t_f obtained by simulating the model in Figure 1 for d = 600 bp and [σ⁷⁰] = 5 μM. b. Coupling efficiency dependence on the distance d between primary operon terminator and secondary operon promoter, for two possible free σ⁷⁰ concentrations. Shaded areas show the 68% C.I.s. c. Distribution of distances between operon final terminators and the nearest operon initial promoter in the E. coli genome determined from data in ref. ²⁹.