IscR, an Fe-S cluster-containing transcription factor, represses expression of Escherichia coli genes encoding Fe-S cluster assembly proteins
IscR, an Fe-S cluster-containing transcription factor, represses expression of Escherichia coli genes encoding Fe-S cluster assembly proteins
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DOI：
10.1073/pnas.251550898
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发表时间：
2001-12-18
影响因子：
11.1
通讯作者：
Kiley, PJ
中科院分区：
文献类型：
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作者：
Schwartz, CJ;Giel, JL;Kiley, PJ
IscR（铁硫簇调节因子）是由位于大肠杆菌Fe-S簇组装蛋白、IscS、IscU和IscA编码基因上游的一个ORF编码的。IscR与MarA/SoxS/Rob转录因子家族成员MarA具有氨基酸相似性。在这项研究中，我们发现IscR作为iscRSUA操纵子的抑制因子，因为删除IscR的菌株增加了该操纵子的表达。此外，体外转录反应证实了IscR在抑制IscR启动子中的直接作用。电子顺磁共振分析表明厌氧分离蛋白含有一个[2Fe-2S]（1+）簇。Fe-S簇似乎对IscR功能很重要，因为在含有Fe-S簇组装基因iscS或hscA零突变的菌株中，IscR表达的抑制显著降低。研究发现，在Fe-S簇组装受损的菌株背景下，IscR活性降低，这表明该蛋白可能是感知细胞Fe-S簇组装状态的一种新的自动调节机制的一部分。
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.