FIG. 3.
In vitro transcription analysis of the sar operon. Lane M, 32P-labeled DNA size markers. The sizes of the individual DNA fragments in bases are indicated on the left. DNA templates (0.02 μg) for the transcription reaction containing the sar P1, P2, or P3 promoters were added to the reaction mixtures. Lanes a and b were from mixtures containing P1; lanes c and d were from mixtures containing P2; and lanes e and f were from mixtures containing P3. The transcription reaction mixtures contained 0.4 U of E. coli core RNA polymerase preincubated with 0.58 μg of Trx-tagged SigB protein (lanes b, d, and f) or with dialysis buffer (lanes a, c, and e). The products of transcription were subjected to electrophoresis on a 6% denaturing polyacrylamide gel and visualized by autoradiography. The arrow indicates the position of the 190-base sar P3 transcript.