Figure 3. Analysis of promoter regulation in vivo by CRP using LacZ fusion.

The predicted CRP-target promoters were inserted into the lacZ expression plasmid to construct a collection of promoter-lacZ fusions. The promoter-dependent expression of LacZ was determined in both wild-type E. coli and crp-defective mutants (Y-axis, β-galactosidase activity in Miller unit). Except for the talA and fbaB promoters (shown under gray background), the activity of all other promoters decreased in the absence of activator CRP, indicating the involvement of CRP as an activator. The newly identified promoters are shown under black background. As references, some known CRP target promoters such as ptsG, dgsA, ptsH and glpF (shown under white background) were examined in parallel under the same conditions.