FIG. 3.

Dependence of k_obs on RNAP concentration for the p_R⁻/p_RM and D10 constructs. The k_obs were determined as a function of [RNAP], and the data were fit to the equation k_obs = (K_B · k_f) [RNAP]/(K_B[RNAP] + 1), where [RNAP] is the concentration of enzyme, K_B is the association constant for RNAP binding to the promoter in a closed complex, and k_f is the first-order rate constant for the conversion of the closed to the open promoter complex. The curves are the result of the fits. Symbols: ■, promoter with the 10-bp deletion; ▿, wild-type DNA that has had the p_R promoter inactivated by the base changes indicated in Fig. 1. The DNA concentration was kept constant (approximately 1 to 2 nM) for all concentrations of RNAP.