This result was dependent on RstA-activated feoAB transcription because Fe ( II ) uptake in the feoA promoter mutant strain reached wild-type levels upon RstA expression ( Fig. 3A ) .
We next compared the mRNA levels of fhuF between the wild-type and feoA promoter mutant strains grown in LB me-dium and found that the lack of RstA-activated feoAB transcription abrogates repression of the Fur target gene even in the strain expressing the RstA protein ( Fig. 3B ) .
The RstA protein maintained wild-type levels of the Fur protein but exceptionally activated transcription of the feoAB operon directly to the feoA promoter .
In sum , our experiments dem-onstrated that the RstA protein activates transcription of the feoAB operon via its direct binding to the feoA promoter .
The labeled wild-type feoA promoter was incubated with increasing concentrations of the RstA protein .