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J Biol Chem. 2000 Aug 11;275(32):24709-14.

Evidence of an unusually long operator for the fur repressor in the aerobactin promoter of Escherichia coli.

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Department of Microbial Biotechnology, Centro Nacional de Biotecnologia CSIC, Campus de Cantoblanco, 28049 Madrid, Spain.


Production of the siderophore aerobactin in Escherichia coli is transcriptionally metalloregulated through the iron-dependent binding of the Fur (ferric uptake regulator) to a large region (>100 base pairs) within the cognate promoter in the pColV-K30 plasmid. We show in this article that such an unusually long operator results from the specific addition of degenerate repeats 5'-NAT(A/T)AT-3' and not from a fortuitous occupation of the DNA adjacent to the primary binding sites by an excess of the repressor. Furthermore, the protection pattern revealed by DNase I and hydroxyl radical footprinting reflected a side-by-side oligomerization of the protein along an extended DNA stretch. This type of DNA-protein interactions is more like those observed in some eukaryotic factors and nucleoid-associated proteins than typical of specific prokaryotic regulators.

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