Assessing the Role of the Active-site Cysteine Ligand in the Superoxide Reductase from Desulfoarculus baarsii

Mathé, Christelle; Weill, Claire; Mattioli, Tony A.; Berthomieu, Catherine; Houée-Levin⊥, Chantal; Tremey, Emilie; Nivière, Vincent

doi:10.1074/jbc.m700279200

“…However, the smaller effect of the C13S mutation on NADPH:superoxide oxidoreductase activity observed here, compared to what was observed for the reduction of SOR by Fpr (Figure 3), could result from the consumption of NADPH being partially rate-limited by superoxide production, as previously noted [30].…”

Section: Rubredoxin Can Replace Iron Center I As Electron Donor To Ircontrasting

confidence: 33%

“…As previously described, oxidation of NADPH can be specifically associated with turnovers of SOR with superoxide [23,30]. As shown in Figure 6, the rate of NADPH:superoxide oxidoreductase activity for the wild-type SOR was determined to be 9.4 µM NADPH oxidized per min.…”

Section: Rubredoxin Can Replace Iron Center I As Electron Donor To Irmentioning

confidence: 88%

“…baarsii 2Fe-SOR [30]. We demonstrated that iron center I could efficiently transfer electrons from the Fpr reductase to the SOR active site, acting as an inter-molecular electronic relay between two molecules of SOR.…”

Section: Introductionmentioning

confidence: 95%

“…It uses NADPH to reduce various electron acceptors such as flavodoxin or ferredoxin in vivo or ferricyanide and cytochrome c in vitro [32]. Fpr has previously been shown to efficiently transfer electrons to the D. baarsii 2Fe-SOR [30] and was used here to study the mechanism of SOR reduction. As shown in Figure 2, in the presence of a catalytic amount of Fpr and NADPH as electron donor, both D. baarsii SOR centers I and II could be fully reduced.…”

Section: Reduction Of Wild-type and Sor Mutant Proteins By Fprmentioning

confidence: 99%

“…The NADPH:superoxide oxidoreductase assays were carried out under aerobic conditions at room temperature, in a 1 ml spectrophotometric cuvette, in the presence of 10 mM Tris-HCl, pH 7.6, 200 μM NADPH, 500 units/ml catalase, 500 μM hypoxanthine, 1 μM of Fpr and 1 µM of SOR [23,30]. Catalase was added in order to remove hydrogen peroxide produced by the SOR reaction and by the xanthine/xanthine oxidase superoxide generating system.…”

mentioning

confidence: 99%

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Intermolecular electron transfer in two-iron superoxide reductase: a putative role for the desulforedoxin center as an electron donor to the iron active site

Bonnot

¹

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Duval

²

,

Lombard

³

et al. 2011

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Superoxide Reductase

Nivière¹,

Bonnot²,

Bourgeois³

2004

Handbook of Metalloproteins

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Superoxide reductase (SOR) is a small bacterial metalloprotein, which is present in the cytoplasm of some anaerobic or microaerophilic microorganisms. SOR is involved in the detoxification of the superoxide radical and catalyzes its one‐electron reduction into hydrogen peroxide. Three different classes of SOR have been identified and structurally characterized. They all contain a similar active site, which consists of an unusual nonheme iron center, coordinated in a square‐pyramidal geometry to four nitrogens from four histidine side chains in the equatorial plane and the sulfur of one cysteine residue along the fifth axial position. In the reduced state, the sixth axial coordinating site of the iron is vacant, suggesting the most obvious site for initial binding of the superoxide substrate. The reaction mechanism of SOR has been studied by pulse radiolysis. SOR reacts specifically at a nearly diffusion‐controlled rate with O 2 •− , generating H 2 O 2 and the oxidized Fe 3+ active site. Reaction intermediates have been observed and proposed to be Fe 3+ ‐(hydro)peroxo species, resulting from the fast electron transfer from the ferrous iron to the superoxide anion and from protonation step. Formation of Fe 3+ ‐(hydro)peroxo intermediate species in the active site of SOR has been supported by resonance Raman spectroscopy and X‐ray structures of iron(III) peroxide species in the SOR from Desulfoarculus baarsii .

show abstract

Superoxide Reductase

Nivière

¹

,

Bonnot

²

,

Bourgeois

³

2011

Encyclopedia of Inorganic and Bioinorganic Chemistry

View full text Add to dashboard Cite

Superoxide reductase (SOR) is a small bacterial metalloprotein, which is present in the cytoplasm of some anaerobic or microaerophilic microorganisms. SOR is involved in the detoxification of the superoxide radical and catalyzes its one‐electron reduction into hydrogen peroxide. Three different classes of SOR have been identified and structurally characterized. They all contain a similar active site, which consists of an unusual nonheme iron center, coordinated in a square‐pyramidal geometry to four nitrogens from four histidine side chains in the equatorial plane and the sulfur of one cysteine residue along the fifth axial position. In the reduced state, the sixth axial coordinating site of the iron is vacant, suggesting the most obvious site for initial binding of the superoxide substrate. The reaction mechanism of SOR has been studied by pulse radiolysis. SOR reacts specifically at a nearly diffusion‐controlled rate with O 2 •− , generating H 2 O 2 and the oxidized Fe 3+ active site. Reaction intermediates have been observed and proposed to be Fe 3+ ‐(hydro)peroxo species, resulting from the fast electron transfer from the ferrous iron to the superoxide anion and from protonation step. Formation of Fe 3+ ‐(hydro)peroxo intermediate species in the active site of SOR has been supported by resonance Raman spectroscopy and X‐ray structures of iron(III) peroxide species in the SOR from Desulfoarculus baarsii .

show abstract

Assessing the Role of the Active-site Cysteine Ligand in the Superoxide Reductase from Desulfoarculus baarsii

Cited by 36 publications

References 36 publications

Intermolecular electron transfer in two-iron superoxide reductase: a putative role for the desulforedoxin center as an electron donor to the iron active site

Intermolecular electron transfer in two-iron superoxide reductase: a putative role for the desulforedoxin center as an electron donor to the iron active site

Superoxide Reductase

Superoxide Reductase

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