FIG. 1.
DNA relaxation and fim switch inversion preferences. (A) Phase-on and -off fim switches, showing inverted repeats IRL and IRR, the PfimA promoter (−10, −35), the fimA transcription start site, and Lrp binding sites 1 and 2. (B) Topoisomers of plasmid pUC18 isolated from E. coli K-12 strain VL386 treated with novobiocin at the concentrations shown. (C) Switch inversion preferences with and without a functional PfimA promoter (structures summarized above each panel) at increasing concentrations of novobiocin. Densitometric data from PCR switch assay gels (insets) were used to plot the graphs. Numbers above each gel lane are μg/ml of novobiocin. Bands corresponding to phase-on or -off are labeled.