1887

Abstract

The influence of iron levels on the transcription of the gene in is the focus of this study. Studies in our laboratory showed HupB to be co-expressed with the two siderophores in low-iron organisms. Mycobactin biosynthesis is repressed by the IdeR–Fe complex that binds the IdeR box in the promoter. Recently, we demonstrated the positive regulatory effect of HupB on mycobactin biosynthesis by demonstrating its binding to a 10 bp HupB box in the promoter. Earlier, we observed that HupB, expressed maximally in low-iron media (0.02 µg Fe ml; 0.36 µM Fe) was still detectable at 8 µg Fe ml (144 µM Fe) when the siderophores were absent and complete repression was seen only at 12 µg Fe ml (216 µM Fe). In this study, we observed elevated levels of transcripts in iron-limited organisms. IdeR, and not FurA, functioned as the iron regulator, by binding to two IdeR boxes in the promoter. Interestingly, the 10 bp HupB box, first reported in the promoter, was identified in the promoter. Using DNA footprinting and electrophoretic mobility shift assays, we demonstrated the functionality of the HupB box and the two IdeR boxes. The high transcript levels expressed by the organism and the protein–DNA interaction studies led us to hypothesize the sequence of events occurring in response to changes in the intracellular iron concentration, emphasizing the roles played by IdeR and HupB in iron homeostasis.

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2014-08-01
2019-10-13
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