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. 2012 Nov 1;17(9):1215–1231. doi: 10.1089/ars.2012.4511

FIG. 8.

FIG. 8.

The IscR regulatory system. Scheme summarizing the mechanism of IscR regulation of isc and suf operons. Under iron replete conditions (upper part of the figure), and when the cellular supply of iron–sulfur clusters is sufficient, cluster-bound IscR represses the housekeeping Isc iron–sulfur biogenesis system in E. coli. When iron–sulfur cluster demand increases, the apo-form of IscR accumulates, leading to depression of the cluster biosynthesis system. Under conditions of low iron or oxidative stress (lower part of the figure), E. coli utilizes a different iron–sulfur biogenesis system encoded by the Suf system. Under inducing conditions, suf operon expression is activated by apo-IscR, which accumulates under conditions of low iron–sulfur cluster supply through both the loss of cluster from cluster-bound IscR and depression of the isc operon, which includes iscR. See section IscR for details. Note that the high-resolution structure of IscR is not yet available, and the schematic representation included here is based on the recently published structure of the Rrf2 family protein CymR (133).

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