FIG. 3.

SC of the leuV(−50 +10) promoter and mutant derivatives. The strains from which RNA was extracted and whether the cultures were treated (+) or not treated (−) with serine hydroxymate (SeOH) to induce the stringent response are shown above the lanes. Transcripts were detected with the test primer which is complementary to β-galactosidase mRNA sequences or with the reference primer complementary to unique plasmid transcripts (see Materials and Methods). These mixtures were electrophoresed in separate wells to avoid overlapping with nonspecific bands. All samples were quantitated by using an ImageQuant PhosphorImager. Actual values (in pixels × 1,000 per microgram of total RNA) of promoter activity were as follows: leuV, 20.8 ± 4.2 before induction and 3 ± 0.7 after induction; 45T, 48.5 ± 5.7 before induction and 7.5 ± 0.65 after induction; D mutant (Dmut), 49 ± 6.8 before induction and 8 ± 0.9 after induction; and A7 mutant, 37.5 ± 5.2 before induction and 13 ± 2.3 after induction. Values reported are the averages of five different independent experiments.