NDLI: Submicromolar hydrogen peroxide disrupts the ability of Fur protein to control free-iron levels in Escherichia coli

Content Provider	PubMed Central
Author	Varghese, Shery Wu, Amy Park, Sunny Imlay, Karin R. C. Imlay, James A.
Abstract	In aerobic environments, mutants of Escherichia coli that lack peroxidase and catalase activities (Hpx−) accumulate sub-micromolar concentrations of intracellular H2O2. We observed that in defined medium these strains constitutively expressed members of the Fur regulon. Iron-import proteins, which Fur normally represses, were fully induced. H2O2 may antagonize Fur function by oxidizing the Fur:Fe2+ complex and inactivating its repressor function. This is a potential problem, as in iron-rich environments excessive iron uptake would endanger H2O2-stressed cells by accelerating hydroxyl-radical production through the Fenton reaction. However, the OxyR H2O2-response system restored Fur repression in iron-replete LB medium by up-regulating the synthesis of Fur protein. Indeed, when the OxyR binding site upstream of fur was disrupted, Hpx− mutants failed to repress transporter synthesis, and they exhibited high levels of intracellular free iron. Mutagenesis and bacteriostasis resulted. These defects were eliminated by mutations or chelators that slowed iron import, confirming that dysregulation of iron uptake was the root problem. Thus aerobic organisms must grapple with a conundrum: how to monitor iron levels in oxidizing environments that might perturb the valence of the analyte. The induction of Fur synthesis by the OxyR response comprises one evolutionary solution to that problem.
Related Links	http://dx.doi.org/10.1111/j.1365-2958.2007.05701.x
Ending Page	830
Page Count	9
Starting Page	822
File Format	PDF
ISSN	0950382X
e-ISSN	13652958
Journal	Molecular microbiology
Issue Number	3
Volume Number	64
Language	English
Publisher Date	2007-05-01
Access Restriction	Open
Subject Keyword	Molecular Biology Microbiology Research in Higher Education
Content Type	Text
Resource Type	Article
Subject	Molecular Biology Microbiology

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The YaaA Protein of the Escherichia coli OxyR Regulon Lessens Hydrogen Peroxide Toxicity by Diminishing the Amount of Intracellular Unincorporated Iron ▿ †

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Submicromolar hydrogen peroxide disrupts the ability of Fur protein to control free-iron levels in Escherichia coli

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