Dual Repression by Fe 2+ -Fur and Mn 2+ -MntR of the mntH Gene, Encoding an NRAMP-Like Mn 2+ Transporter in Escherichia coli
Open Access
- 15 August 2001
- journal article
- Published by American Society for Microbiology in Journal of Bacteriology
- Vol. 183 (16) , 4806-4813
- https://doi.org/10.1128/jb.183.16.4806-4813.2001
Abstract
The uptake of Mn 2+ , a cofactor for several enzymes in Escherichia coli , is mediated by MntH, a proton-dependent metal transporter, which also recognizes Fe 2+ with lower affinity. MntH belongs to the NRAMP family of eukaryotic Fe 2+ and Mn 2+ transporters. In E. coli strains with chromosomal mntH-lacZ fusions, mntH was partially repressed by both Mn 2+ and Fe 2+ . Inactivation of fur resulted in the loss of Fe 2+ -dependent repression of mntH transcription, demonstrating that Fe 2+ repression depends on the global iron regulator Fur. However, these fur mutants still showed Mn 2+ -dependent repression of mntH . The Mn 2+ -responsive transcriptional regulator of mntH was identified as the gene product of o155 (renamed MntR). mntR mutants were impaired in Mn 2+ but not Fe 2+ repression of mntH transcription. Binding of purified MntR to the mntH operator was manganese dependent. The binding region was localized by DNase I footprinting analysis and covers a nearly perfect palindrome. The Fur binding site, localized within 22 nucleotides of the mntH operator by in vivo operator titration assays, resembles the Fur-box consensus sequence.Keywords
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