The gal promoter region of E. coli
showing the P1 and P3 promoters in the
plasmid pSA852 (D. Lewis, unpublished data). pSA852 contains a 288-bp
segment of the gal control region (−197 to +91)
followed by a transcription terminator (21). The CRP binding site is in
bold. The transcription start site of P1 is denoted as
+1. The −10 region, the P1 promoter, is in bold and
boxed, and that of P3 is boxed. The adenine residues
with the asterisks were replaced individually by 2-AP in the
106-base-long rightward primer. DNA templates (385 bp) for in
vitro transcription containing 2-AP were generated by PCR using
the rightward and leftward primers (shown by arrows) from pSA852. The
106-base-long primer also contained −20T to G and −19T to G changes
to inactivate the P2 promoter. T, transcription
termination signal.