Transcription start sites were determined by primer extension experiments with RNA isolated from V.anguillarum H775-3, a strain deficient in anguibactin biosynthesis. The authors identified a putative Fur box based on E.coli Fur box consensus. Primer extension analysis with RNA obtained from V.anguillarum H775-3 grown in iron rich conditions suggested Fur-mediated repression of huvA since no signal was observed. Similarly, the huvXZ and tonB1exbB1D1-huvBCD genes were shown to be regulated by Fur. Fur-mediated repression of these genes was confirmed by measuring the β-galactosidase activities of uvA∷lacZ, huvX∷lacZ and tonB1∷lacZ. The results of this assay showed that expression was high in low-iron medium and low after the addition of iron to the medium. Additionally, lacZ reporter assay in the fur mutant strain showed that β-galactosidase activity was high under both high- and low-iron conditions.
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|