SoxRS

Gaudu, P., Moon, N., and Weiss, B. 1997. Regulation of the soxRS oxidative stress regulon. The Journal of Biological Chemistry 272 5082-5086. 

SoxR, OxyR Fur LAC9 Acel —rather uniform results showing activation -de-repression of genes that are under the control of Fur —attenuated DNA-binding in vitro —inhibition of DNA-binding in yeast... 

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

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],... 

SoxR in the reduced state in the cell. Detailed understanding of molecular mechanism of transcription activation by SoxR awaits structural refinement. 

Ding H, Demple B. Direct nitric oxide signal transduction via nitrosylation of iron-sulfur centers in the SoxR transcription activator. P. Natl. Acad. Sci. 2000 97 5146-5150. 

In procaryotes, short upstream regulatory sequences (generally less than 100 bp) known as antioxidant response elements (AREs) control the expression of antioxidant enzymes. In E. coli, up-regulation of SODs involves soxR and soxS gene products [69]. 

A model (Figure 11-1) has thus emerged in which SoxR exists in a dynamic equilibrium linked both to chemical oxidation and reduction, presumably enzymatic. This model can explain the rapid shifts from inactive to active SoxR, and back again [29]. It does not necessarily require specific oxidizing species, as both oxygen and superoxide might be capable of the activating reaction under aerobic conditions [30]. However, the soxRS system is also activated upon cellular exposure to NO, which is even more effective under anaerobic conditions where NO is not... 

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.

The studies of bacterial oxidative stress responses have been very important in several respects. The oxyR and soxRS systems show how dynamic modulation of gene expression can help counteract both metabolic oxidants and oxidative stress imposed by environmental agents. These systems have potential importance in aspects of clinical infections, as noted above. More broadly, the molecular characterization of OxyR and of SoxR have provided key models for understanding how transcrip-... 

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