SoxR protein

SoxF protein, 47 89-90 SoxL protein, 47 89-90 SoxR protein, 47 480-481 Soybeans, leghemoglobin in, 46 495-501, see also Leghemoglobin... 

Figure 11-1 Model for redox regulation of the soxRS regulon. The SoxR [2Fe-2S] centers are in the reduced state, probably maintained enzymatically, in the absence of oxidative stress. Reduced SoxR binds its DNA target in the soxS promoter, but does not stimulate transcription. Oxidative stress caused by superoxide-generating agents or nitric oxide leads to oxidation of the [2Fe-2S] centers, and an allosteric transition in the SoxR protein-5ox5 DNA complex that strongly stimulates transcription.

Transcriptional regulation of antioxidant proteins. Certain proteins with easily accessible Fe-S clusters, e.g., aconitase, are readily inachvated by oxidants such as perox5mitrite. At least two proteins of this type function as transcription factors in E. coli. These are known as SoxR and OxyR. The SoxR protein is sensihve to superoxide anion, which carries out a one-electron oxidahon on its Fe2S2 centers. ... 

Hidalgo E, Bollinger JM Jr et al (1995) Binuclear[2Fe-2S] clusters in the Escherichia coli SoxR protein and role of the metal centers in transcription. J Biol Chem 270 20908-20914... 

NADH, reduced nicotinamide-adenine dinueleotide Q, coenzyme Q FNR, fumarate nitrate reduction SoxR, superoxide activated regulatory protein IRP, iron regulatory protein NIFU, nitrogen fixation gene U product. 

Relatively recently Fe/S proteins have been found to function in the regulation of biosynthesis. This can be by promoting deoxyribonucleic acid (DNA) transcription, e.g. the [2Fe-2S] containing Escherichia coli superoxide-activated (SoxR) transcription activator [10-12], or the presumably [4Fe-4S]-containing E. coli transcription factor fumarate nitrate reduction (FNR) [13,14], Alternatively, the Fe/S protein can act by interference with messenger ribonucleic acid (mRNA) translation, i.e., the iron regulatory proteins (IRPs) [15,16], These interactions are stoichiometric, therefore not catalytic. Presumably, they are also a form of sensoring, namely, of oxidants and/or iron [17],... 

In E. coli catalases are up-regulated by the redox-sensitive oxyR protein, which in its oxidized state binds to AREs, while up-regulation of SODs involves soxR and soxS gene products [69]. 

An excellent example of the regulatory function of Fe-S clusters, can be found in SoxR, which is discussed by Demple in Chapter 11. This protein is a [2Fe-2S] cluster-containing transcriptional regulator, which is activated by oxidative stress through the oxidation of its iron-sulfur centers, thus acting thus as a regulatory redox switch. 

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