Redox Regulation

PerR Regulated by Histidine Oxidation

Science's STKE  21 Mar 2006:
Vol. 2006, Issue 327, pp. tw98
DOI: 10.1126/stke.3272006tw98

Both prokaryotes and eukaryotes respond to oxidative stress by increasing the expression of genes that detoxify reactive oxygen species. Lee and Helmann show that Bacillus subtilis PerR, which is a transcriptional repressor of the PerR regulon, undergoes peroxide-stimulated iron-catalyzed histidine oxidation, which causes the protein to dissociate from DNA, allowing the PerR-regulated genes to be expressed. PerR is a dimer that under native conditions contains one Zn2+ and one Fe2+ per subunit. Lee and Helmann modeled the PerR structure on FurPA, a homolog from Pseudomonas aeruginosa, and predicted that four cysteines formed a binding site for Zn2+ and three histidines and two aspartic acid residues formed a binding site for Fe2+ (or Mn2+). Mutational analysis confirmed that these nine residues were essential for peroxide-mediated derepression of a reporter gene. PerR bound to Fe2+ became oxidized and dissociated from DNA (based on electrophoretic mobility shift assay and fluorescence anisotropy measurements) in response to peroxide, whereas PerR bound to Mn2+ in place of Fe2+ did not. In the presence of Fe2+ and aerobic conditions, the protein was oxidized and the oxidation did not influence the accessibility of the cysteine residues to iodoacetamide, which indicated that they were not oxidized. Mass spectrometry analysis and mutational analysis in vivo demonstrated that His37 and His91, which are also involved in Fe2+ coordination, were the sites of oxidation. The data suggest that peroxide triggers the metal-catalyzed formation of 2-oxo-histidine in PerR, which allows expression of peroxide-defense genes. Histidine oxidation is a new mechanism of peroxide sensing, with most other redox-sensitive proteins, thus far studied, modified on cysteine residues.

J.-W. Lee, J. D. Helmann, The PerR transcription factor senses H2O2 by metal-catalysed histidine oxidation. Nature 440, 363-367 (2006). [PubMed]