tonB3-lacZ fusion assays showed that tonB3 expression was significantly lower in the lrp mutant strain that in the wild type strain. EMSA confirmed that Lrp bound specifically to the tonB3 promoter region. DNase I footprinting assay showed that Lrp protected three regions in the tonB3 promoter that overlap sequences with similarity to the Lrp consensus. LacZ transcriptional fusions constructed with tonB3 promoter in which the binding regions identified by DNase I footprinting were deleted showed that the expression of tonB3 promoter was abolished in the absence of these sequences. LacZ reporter assays showed that tonB3 expression was reduced at least 10 fold in the lrp mutant compared to the wild type strain.
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|