IscR, an Fe-S Cluster-containing Transcription Factor, Represses Expression of Escherichia Coli Genes Encoding Fe-S Cluster Assembly Proteins

Overview

Journal Proc Natl Acad Sci U S A

Specialty Science

Date 2001 Dec 14

PMID 11742080

Citations 198

Authors

C J Schwartz

J L Giel

T Patschkowski

C Luther

F J Ruzicka

H BEINERT

P J Kiley

Affiliations

Soon will be listed here.

Abstract

IscR (iron-sulfur cluster regulator) is encoded by an ORF located immediately upstream of genes coding for the Escherichia coli Fe-S cluster assembly proteins, IscS, IscU, and IscA. IscR shares amino acid similarity with MarA, a member of the MarA/SoxS/Rob family of transcription factors. In this study, we found that IscR functions as a repressor of the iscRSUA operon, because strains deleted for iscR have increased expression of this operon. In addition, in vitro transcription reactions established a direct role for IscR in repression of the iscR promoter. Analysis of IscR by electron paramagnetic resonance showed that the anaerobically isolated protein contains a [2Fe-2S](1+) cluster. The Fe-S cluster appears to be important for IscR function, because repression of iscR expression is significantly reduced in strains containing null mutations of the Fe-S cluster assembly genes iscS or hscA. The finding that IscR activity is decreased in strain backgrounds in which Fe-S cluster assembly is impaired suggests that this protein may be part of a novel autoregulatory mechanism that senses the Fe-S cluster assembly status of cells.

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