Figure 3.

Activation of P_RM by wild-type and mutant λcI dimers bound at nonadjacent operator sites. Strains AH-5.9 (in-phase reporter) and AH-5.5 (out-of-phase reporter) were transformed with derivatives of plasmid pA3B2 (A) or pLR2 (B) encoding wild-type or mutant derivatives of λcI. Fold activation was determined by calculation of the ratio of β-galactosidase activity observed in each case to that observed in cells transformed with a control plasmid that lacks the λcI gene. β-Galactosidase activities in the control cultures were between 1.6 and 2.5 Miller units in all cases. Results are averages of duplicate assays, which varied by less than ±6.5% from the mean.