Abdelnasser El Ghazouani
Biochemical and functional characterizations of the PerR protein (Bacillus subtilis): A bacterial sensor of hydrogen peroxide
Published on 13 November 2007
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Thesis presented November 13, 2007
Abstract:
The PerR (Peroxyde resistance Regulator) metalloprotein is a transcription factor described as a H2O2 sensor in many micro-organisms. The PerR protein from
Bacillus subtilis, isolated in its apo form contains one Zn2+ ion per monomer. Under normal growth conditions, PerR is partially oxidized and inactive in terms of DNA binding. Mass spectrometry and EPR spectroscopy allowed us to connect the metal binding capacity of PerR towards Fe2+ or Mn2+ and its oxidation state. A new expression protocol which leads to a fully reduced form of the protein has been established. It allows the reliable determination of the affinity of the protein for the regulatory metal and the DNA target. The apo-PerR-Zn form has been crystallized and the structure reveals that the Zn2+ ion is part of a structural site. The zinc atom is coordinated in a tetrahedral geometry by the four cysteine residues of the protein (Zn(Cys)4). This site locks the dimerization domain and increases the dimer stability. The structural role of the zinc site has been confirmed by biochemical experiments which showed a poor reactivity toward H2O2. Fluorescence spectroscopy experiments indicated conformational changes of PerR during manganese incorporation and DNA binding. The formation of the DNA-PerR complex has been studied in more details. Two nucleotides and three amino acids have been shown to be crucial in this interaction. Finally, our work on the oxidized form of PerR showed that the 2-oxo-histidine modified residue is the biological marker of PerR oxidation.
Keywords:
H2O2, PerR, Oxidative stress, 2-oxo
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