FIG. 4.
The near-consensus −35 hexamer in the PexsC promoter is not required for ExsA-independent transcription. (A) Diagram showing the mutant PexsC promoter derivatives used in this experiment. The −35, extended −10, and −10 elements are boxed, and the individual point mutations are in bold. (B) Single-round in vitro transcription assays showing ExsA-independent transcription from PexsC derivatives containing −35 (G41T, T40A, G39C, A38T, C37G, A36T, and A33G), extended −10 (TG), and −10 (T8G) point mutations. Reactions were performed as described in the legend to Fig. 3, except open complexes were allowed to form for 20 min in the absence of ExsA. (C) Quantification of the in vitro transcription data shown in panel B. The amount of exsC transcript produced in each experiment was normalized to an ExsA-independent transcript (64) produced from a weak promoter on the minicircle backbone. The reported values are the averages from three independent experiments, and error bars represent the standard errors of the means.