A glutamate bridge is essential for dimer stability and metal selectivity in manganese superoxide dismutase

Mei M. Whittaker, James W. Whittaker

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Abstract

In Escherichia coli manganese superoxide dismutase (MnSOD), the absolutely conserved Glu170 of one monomer is hydrogen-bonded to the Mn ligand His171 of the other monomer, forming a double bridge at the dimer interface. Point mutation of Glu170 → Ala destabilizes the dimer structure, and the mutant protein occurs as a mixture of dimer and monomer species. The purified E170A MnSOD contains exclusively Fe and is devoid of superoxide dismutase activity. E170A Fe2-MnSOD closely resembles authentic FeSOD in terms of spectroscopic properties, anion interactions and pH titration behavior. Reconstitution of E170A Fe2-MnSOD with Mn(II) salts does not restore superoxide dismutase activity despite the spectroscopic similarity between E170A Mn2-MnSOD and wild type Mn2-MnSOD. Growth of sodA+ and sodA- E. coli containing the mutant plasmid pDT1-5(E170A) is impaired, suggesting that expression of mutant protein is toxic to the host cells.

Original languageEnglish (US)
Pages (from-to)22188-22193
Number of pages6
JournalJournal of Biological Chemistry
Volume273
Issue number35
DOIs
StatePublished - Aug 28 1998

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ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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