Functional differences between manganese and iron superoxide dismutases in Escherichia coli K-12

Karen A. Hopkin, Madeline A. Papazian, Howard M. Steinman

Research output: Contribution to journalArticle

71 Citations (Scopus)

Abstract

Superoxide dismutases are enzymes that defend against oxidative stress through decomposition of superoxide radical. Escherichia coli contains two highly homologous Superoxide dismutases, one containing manganese (MnSOD) and the other iron (FeSOD). Although E. coli Mn and FeSOD catalyze the dismutation of Superoxide with comparable rate constants, it is not known if they are physiologically equivalent in their protection of cellular targets from oxyradical damage. To address this issue, isogenic strains of E. coli containing either Mn or FeSOD encoded on a plasmid and under the control of tac promoter were constructed. SOD specific activity in the Mn and FeSOD strains could be controlled by the concentration of isopropyl β-thiogalactoside in the medium. The tolerance of these strains to oxidative stress was compared at equal Mn and FeSOD specific activities. Our results indicate that E. coli Mn and FeSOD are not functionally equivalent. The MnSOD is more effective than FeSOD in preventing damage to DNA, while the FeSOD appears to be more effective in protecting a cytoplasmic superoxide-sensitive enzyme. These data are the first demonstration that Mn and FeSOD are adapted to different antioxidant roles in E. coli.

Original languageEnglish (US)
Pages (from-to)24253-24258
Number of pages6
JournalJournal of Biological Chemistry
Volume267
Issue number34
StatePublished - Dec 5 1992

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Escherichia coli
Superoxide Dismutase
Superoxides
Oxidative stress
Oxidative Stress
Isopropyl Thiogalactoside
Enzymes
Manganese
DNA Damage
Rate constants
Plasmids
Demonstrations
Iron
Antioxidants
Decomposition
DNA

ASJC Scopus subject areas

  • Biochemistry

Cite this

Functional differences between manganese and iron superoxide dismutases in Escherichia coli K-12. / Hopkin, Karen A.; Papazian, Madeline A.; Steinman, Howard M.

In: Journal of Biological Chemistry, Vol. 267, No. 34, 05.12.1992, p. 24253-24258.

Research output: Contribution to journalArticle

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abstract = "Superoxide dismutases are enzymes that defend against oxidative stress through decomposition of superoxide radical. Escherichia coli contains two highly homologous Superoxide dismutases, one containing manganese (MnSOD) and the other iron (FeSOD). Although E. coli Mn and FeSOD catalyze the dismutation of Superoxide with comparable rate constants, it is not known if they are physiologically equivalent in their protection of cellular targets from oxyradical damage. To address this issue, isogenic strains of E. coli containing either Mn or FeSOD encoded on a plasmid and under the control of tac promoter were constructed. SOD specific activity in the Mn and FeSOD strains could be controlled by the concentration of isopropyl β-thiogalactoside in the medium. The tolerance of these strains to oxidative stress was compared at equal Mn and FeSOD specific activities. Our results indicate that E. coli Mn and FeSOD are not functionally equivalent. The MnSOD is more effective than FeSOD in preventing damage to DNA, while the FeSOD appears to be more effective in protecting a cytoplasmic superoxide-sensitive enzyme. These data are the first demonstration that Mn and FeSOD are adapted to different antioxidant roles in E. coli.",
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AB - Superoxide dismutases are enzymes that defend against oxidative stress through decomposition of superoxide radical. Escherichia coli contains two highly homologous Superoxide dismutases, one containing manganese (MnSOD) and the other iron (FeSOD). Although E. coli Mn and FeSOD catalyze the dismutation of Superoxide with comparable rate constants, it is not known if they are physiologically equivalent in their protection of cellular targets from oxyradical damage. To address this issue, isogenic strains of E. coli containing either Mn or FeSOD encoded on a plasmid and under the control of tac promoter were constructed. SOD specific activity in the Mn and FeSOD strains could be controlled by the concentration of isopropyl β-thiogalactoside in the medium. The tolerance of these strains to oxidative stress was compared at equal Mn and FeSOD specific activities. Our results indicate that E. coli Mn and FeSOD are not functionally equivalent. The MnSOD is more effective than FeSOD in preventing damage to DNA, while the FeSOD appears to be more effective in protecting a cytoplasmic superoxide-sensitive enzyme. These data are the first demonstration that Mn and FeSOD are adapted to different antioxidant roles in E. coli.

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