Transcriptional regulation of Mn-superoxide dismutase gene (sodA) of Escherichia coli is stimulated by DNA gyrase inhibitors (original) (raw)
Related papers
Archives of Biochemistry and Biophysics, 1992
The expression of manganese-containing superoxide dismutase (sodA) in Escherichia coli using sodA : : 1acZ gene fusion was found to he stimulated by DNA gyrase inhibitors, nalidixic acid, or coumermycin Al. Aerobically, the gyrase inhibitors increased the expression of sodA : : 1acZ in the presence or absence of either paraquat or the iron chelator 2,2'-dipyridyl. The concentrations of the inhibitors used were found to reduce DNA supercoiling. Treatment of wild-type cells (sodA+) with nalidixic acid increased the transcription of MnSOD mRNA. Anaerobically, the expression of sodA: : 1acZ in wild-type cells was not affected by nalidixic acid. However, nalidixic acid had a stimulatory effect on the anaerobic expression of sodA : : 1acZ in cells preinduced by the iron chelator as well as in mutants derepressed in sodA expression by virtue of their lacking the transacting repressor proteins or the cis-acting regulatory elements needed for sodA regulation. The results indicate that the effect of DNA gyrase inhibitors is secondary to the cisand trans-regulatory elements of sodA and suggest that changes in DNA topology may affect transcriptional regulation of sodA.
Fems Microbiology Reviews, 1994
Abstract: Aerobic life-style offers both benefits and risks to living cells. The major risk comes from the formation of reactive oxygen intermediates (i.e. superoxide radical, O−2; hydrogen peroxide, H2O2; and hydroxyl radical, OH) during normal oxygen metabolism. However, living cells are able to cope with oxygen toxicity by virtue of a unique set of antioxidant enzymes that scavenge O−2 and H2O2, and prevent the formation OH. Superoxide dismutases (SODs; EC 1.15.1.1) are metalloenzymes essential for aerobic survival. Escherichia coli contains two forms of this enzyme: an iron-containing enzyme (FeSOD) and a manganese-containing enzyme (MnSOD). In E. Coli, MnSOD biosynthesis is under rigorous control. The enzyme is induced in response to a variety of environmental stress conditions including exposure to oxygen, redox cycling compounds such as paraquat which exacerbate the level of intracellular superoxide radicals, iron chelation (i.e. iron deprivation), and oxidants. A model for the regulation of the MnSOD has been proposed in which the MnSOD gene (sodA) is negatively regulated at the level of transcription by an iron-containing redox-sensitive repressor protein. The effect of ironchelation most probably results in removal of the iron necessary for repressor activity. Recent studies have shown that sodA expression is regulated by three iron-dependent regulatory proteins, Fur (ferric uptake regulation), Fnr (fumarate nitrate regulation) and SoxR (superoxide regulon), and by the ArcA/ArcB (aerobic respiratkm control) system. The potential Fur-, Fnr- and AreA-binding sites in the sodA promoter region have bcen identified by using different cis-acting regulatory mutations that caused anaerobic derepression of the gene. An updated model is presented to accommodate these findings and explain the biological significance of regulation by multi-regulatory elements in response to multi-environmental effectors.
Transcriptional activation of Mn-superoxide dismutase gene (sodA) of Escherichia coli by MnCl2
Biochimica et Biophysica Acta (BBA) - Gene Structure and Expression, 1993
Transcription of the manganese-superoxide dismutase gene (sodA) in Escherichia coli was shown to be activated by manganese. Addition of MnCI z increased the expression of/3-galactosidase from a sodA::lacZ protein fusion and increased the concentration of mRNA transcribed from sodA + and sodA::lacZ constructs. The stimulatory affect of manganese on the expression of sodA::lacZ was greatly reduced (i.e., > 90%) in a strain harboring a fur mutation. We also found that manganese was capable of altering DNA topology. These results show that Mn z+ causes activation of soda transcription.
Fems Microbiology Letters, 1984
Abstract Nalidixic acid caused a significant increase in the Mn-containing superoxide dismutase (MnSOD) of Escherichia coli. The maximum stimulatory effect of nalidixic acid on MnSOD biosynthesis was observed at 0.1 mM. The stimulatory effect of nalidixic acid was not due to increases in the intracellular flux of O−2, but rather to its ability to chelate Fe2+. Furthermore, 2,2′-dipyridyl and 1,10-phenanthroline were shown to cause a 7- to 20-fold increase in the MnSOD of E. coli. It is proposed that the repressor for MnSOD is an iron-containing protein.
Current Microbiology, 1992
Escherichia coli strains harboring trans-acting mutations affecting the expression of Mn-superoxide dismutase (SOD) gene (sodA) were used to study soda regulation. Complementation studies revealed that either arc (aerobic respiratory control) or fur (ferric uptake regulation) loci independently complemented anaerobic expression of a sodA :: lacZ protein fusion in one mutant strain (UV16). This mutant exhibited phenotypes (i.e., elevated outer membrane proteins, enzyme activity, and dye sensitivity) typical of fur and arc mutants. When these mutations were introduced into an otherwise wild-type background, anaerobic sodA expression occurred only when both arc and fur mutations were present simultaneously, suggesting cooperative roles of Fur and Arc in sodA repression. The reconstructed fur arcA and fur arcB double mutants were still inducible by iron chelators, suggesting the possible involvement of another iron-containing repressor protein. A second independent mutant strain harboring a trans-acting regulatory mutation (UV14) was only partially complemented by multicopy plasmids carrying fur + or arc + genes, implicating other genetic elements in sodA regulation.
Proceedings of The National Academy of Sciences, 1992
Transcriptional regulation of the sodA gene, encoding the manganese superoxide dismutase (superoxide: superoxide oxidoreductase, EC 1.15.1.1) of Escherchia coli, was studied by monitoring expression of sodA-lacZ in different genetic backgrounds and under different growth conditions. Mutations in the fnr gene were found to affect aerobic and anaerobic expression of sodA-wacZ. Potential Fnr-binding sites were identified in the promoter region of sodA. Strains harboring simultaneous mutations in arcAiB and fur expressed sodA-lacZ under anaerobic growth conditions but were still inducible by iron chelators. However, in the triple mutants (fnr fur arcAiB) sodA-lacZ was fully expressed under anaerobiosis and was not further induced by the presence of 2,2'-dipyridyl, nitrate, or oxidants. On the other hand, aerobic expression of sodA-lacZ from a Fur-strain was -3.8-fold higher than that
Biosynthesis and regulation of superoxide dismutases
Free Radical Biology and Medicine, 1988
The past two decades have witnessed an explosion in our understanding of oxygen toxicity. The discovery of superoxide dismutases (SODs) (EC. 1.15.1.1), which specifically catalyze the dismutation of superoxide radicals (02-) to hydrogen peroxide (H202) and oxygen, has indicated that O2-is a normal and common byproduct of oxygen metabolism. There is an increasing evidence to support the conclusion that superoxide radicals play a major role in cellular injury, mutagenesis, and many diseases. In all cases SODs have been shown to protect the cells against these deleterious effects. Recent advances in molecular biology and the isolation of different SOD genes and SOD c-DNAs have been useful in. proving beyond doubt the physiological function of the enzyme. The biosynthesis of SODs, in most biological systems, is under rigorous controls. In general, exposure to increased pO2, increased intracellular fluxes of O2-, metal ions perturbation, and exposures to several environmental oxidants have been shown to influence the rate of SOD synthesis in both prokaryotic and eukaryotic organisms. Recent developments in the mechanism of regulation of the manganese-containing superoxide dismutase of Escherichia coli will certainly open new research avenues to better understand the regulation of SODs in other organisms.
Archives of Biochemistry and Biophysics, 2002
Escherichia coli, lacking cytoplasmic superoxide dismutases, exhibits a variety of oxygen-dependent phenotypic deficits. Enrichment of the growth medium with Mn(II) relieved those deficits. Extracts of cells grown on Mn(II)-rich medium exhibited superoxide dismutase-like activity that was due partially to low-molecular-weight and partially to high-molecular-weight complexes. The high-molecular-weight activity was sensitive to proteolysis. Hence this activity is likely associated with low-affinity binding of Mn to proteins.