Third , the RstA-dependent activation of feoAB transcription increased Fe ( II ) uptake , whereas mutation of the RstA-binding sequences on the feoA promoter or deletion of the feoB gene abolished repression of Fur-regulated genes in cells expressing the RstA protein ( Fig. 3 ) .
However , given that the Fur regulators can efficiently control feoB mRNA levels in response to different levels of iron , the reason remains unknown .
However , given that the Fur regulators can efficiently control feoB mRNA levels in response to different levels of oxygen , the reason remains unknown .