FIG. 6.
Transcriptional activation by λcI-AsiA in the presence of the α-ς chimeras. (A) Schematic diagram of test promoter placCOP-93+OL2-62 used to determine the effects of substitutions in the α-ς chimeras on transcriptional activation by λcI-AsiA. The test promoter placCOP-93+OL2-62 bears both a consensus λ operator and OL2 centered 93 and 62 bp, respectively, upstream from the transcriptional start site of the lac core promoter. In reporter strain F′93+62 the placCOP-93+OL2-62 test promoter is located on an F′ episome and drives expression of a linked lacZ gene. (B) Effect of λcI-AsiA on transcription in vivo from placCOP-93+OL2-62 in the presence of the α-ς chimeras. F′93+62 cells harboring compatible plasmids expressing the indicated proteins were grown in the presence of different concentrations of IPTG and assayed for β-galactosidase activity. ΔcI refers to the fact that no λcI was made by control plasmid pACΔcI.