Abstract
Escherichia coli responds to superoxide-generating agents by inducing approximately 40 proteins. We have identified a genetic locus, soxR (superoxide response), that positively regulates 9 of these proteins during superoxide stress. Induction under soxR control is at the transcriptional level, as shown with lac fusions to five paraquat-inducible promoters. Members of the soxR regulon include at least three proteins with demonstrable antioxidant roles: Mn-containing superoxide dismutase (which destroys superoxide radicals), endonuclease IV (which repairs radical-induced damages in DNA), and glucose-6-phosphate dehydrogenase (which produces NADPH). Induction of the soxR regulon also leads to diminished levels of the major outer membrane protein OmpF and alteration of the small-subunit ribosomal protein S6. These latter changes confer resistance to a variety of antibiotics. The soxR regulon may thus operate as an inducible defense against xenobiotics in general.
Publication types
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Anti-Bacterial Agents / pharmacology
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Antioxidants / pharmacology*
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Chromosome Deletion
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Cloning, Molecular
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DNA Transposable Elements*
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DNA-(Apurinic or Apyrimidinic Site) Lyase
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Deoxyribonuclease IV (Phage T4-Induced)
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Drug Resistance, Microbial / genetics
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Endodeoxyribonucleases / genetics*
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Escherichia coli / drug effects
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Escherichia coli / genetics*
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Escherichia coli Proteins*
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Gene Expression Regulation, Bacterial
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Genes, Bacterial
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Genes, Regulator*
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Glucosephosphate Dehydrogenase / genetics*
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Methylnitronitrosoguanidine / pharmacology
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Operon*
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R Factors
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Superoxide Dismutase / genetics*
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Superoxides / metabolism
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Superoxides / pharmacology*
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Transduction, Genetic
Substances
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Anti-Bacterial Agents
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Antioxidants
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DNA Transposable Elements
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Escherichia coli Proteins
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Superoxides
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Methylnitronitrosoguanidine
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Glucosephosphate Dehydrogenase
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Superoxide Dismutase
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Endodeoxyribonucleases
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Deoxyribonuclease IV (Phage T4-Induced)
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endonuclease IV, E coli
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DNA-(Apurinic or Apyrimidinic Site) Lyase