flgB transcription start site was determined by S1 nuclease protection assays. Visual sequence inspection of the flgB promoter identified the presence of a consensus CtrA binding sequence (TTAA-N7-TTAA). DNase I footprinting confirmed that CtrA interacts with the flgB promoter by binding to a 28-bp region. Comparison of the expression levels by beta-gal reporter assays in the wild-type and ctrA temperature-sensitive C. crescentus strains, indicated that CtrA represses flgB expression and activates fliO-fliP expression. Additionally, B-Galactosidase activity was measured from the promoters containing mutations within the consensus CtrA binding sequence and outside of it. The authors report that the results of this analysis were complex. Among the results obtained from these site-directed mutagenesis experiments, it was shown that mutation in the conserved TTAA to GCAA had a deleterious effect on both flgB and fliO-fliP expression.
Regulated genes for each binding site are displayed below. Gene regulation diagrams show binding sites, positively-regulated genes, negatively-regulated genes, both positively and negatively regulated genes, genes with unspecified type of regulation. For each indvidual site, experimental techniques used to determine the site are also given.
|Site sequence||Regulated genes||Gene diagram||Experimental techniques||TF function||TF type|
|TTAATGCCGGATTAA||fliO, fliP, flgB,||