1887

Abstract

Mutations in of have been shown to deregulate expression of several genes that are normally repressed by iron. A conserved sequence, the iron-responsive operator (IRO), was identified near promoters of (involved in the synthesis of the siderophore vicibactin), (specifies an ECF factor needed for vicibactin synthesis) and the two genes (encoding vicibactin receptor). Removal of these IRO sequences abolished Fe-responsive repression. Most of these genes were constitutively expressed in the heterologous host, , but introduction of the cloned gene repressed expression of these genes in this heterologous host if the corresponding IRO sequences were also intact. These observations are the first to examine the mechanisms of RirA, which has no sequence similarity to well-known iron-responsive regulators such as Fur or DtxR. They provide strong circumstantial evidence that RirA is a transcriptional regulator that binds to -acting regulatory sequences near the promoters of at least some of the genes whose expression it controls in response to Fe availability.

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2004-12-01
2019-11-19
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