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In vivo parameters influencing 2-Cys Prx oligomerization: The role of enzyme sulfinylation.

Noichri Y, Palais G, Ruby V, D'Autreaux B, Delaunay-Moisan A, Nyström T, Molin M, Toledano MB - Redox Biol (2015)

Bottom Line: The critical molecular event allowing the peroxidase to chaperone switch is thought to be the enzyme assembly into high molecular weight (HMW) structures brought about by enzyme hyperoxidation.How hyperoxidation promotes HMW assembly is not well understood and Prx mutants allowing disentangling its peroxidase and chaperone functions are lacking.Our data confirm the strict causative link between H2O2-induced hyperoxidation and HMW formation/stabilization, also raising the question of whether CP hyperoxidation triggers the assembly of HMW structures by the stacking of decamers, which is the prevalent view of the literature, or rather, the stabilization of preassembled stacked decamers.

View Article: PubMed Central - PubMed

Affiliation: Oxidative Stress and Cancer, IBITECS, SBIGEM, CEA-Saclay, 91191 Gif-sur-Yvette, France.

No MeSH data available.


Related in: MedlinePlus

The peroxidatic cycle of eukaryotic 2-Cys Prxs. Eukaryotic typical 2-Cys Prx are obligate dimers with a mechanism involving two Cys residues, in which CP decomposes H2O2 into H2O by nucleophilic attack and is oxidized to a sulfenic acid (CP-SOH). The sulfenic acid then reacts with the resolving Cys (CR) residue of the other subunit to form an intermolecular disulfide [48]. This disulfide is then reduced by thioredoxin, which completes the catalytic cycle. Alternatively, when H2O2 levels raises, the CP-SOH can further react with H2O2, which leads to formation of a CP-sulfinic acid (CP-SO2H). The latter is reversed back to CP-SOH by ATP-dependent reduction by sulfiredoxin (Srx).
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f0005: The peroxidatic cycle of eukaryotic 2-Cys Prxs. Eukaryotic typical 2-Cys Prx are obligate dimers with a mechanism involving two Cys residues, in which CP decomposes H2O2 into H2O by nucleophilic attack and is oxidized to a sulfenic acid (CP-SOH). The sulfenic acid then reacts with the resolving Cys (CR) residue of the other subunit to form an intermolecular disulfide [48]. This disulfide is then reduced by thioredoxin, which completes the catalytic cycle. Alternatively, when H2O2 levels raises, the CP-SOH can further react with H2O2, which leads to formation of a CP-sulfinic acid (CP-SO2H). The latter is reversed back to CP-SOH by ATP-dependent reduction by sulfiredoxin (Srx).

Mentions: 2-Cys Prx are obligate head-to-tail B-type homodimers, each with two catalytic Cys residues. In the peroxidatic cycle, the N-terminal Cys, named CP for peroxidatic Cys, reduces H2O2, and is in turn oxidized to a sulfenic acid (CP-SOH) [48] (Fig. 1). The Cys-sulfenic acid moiety then condenses with the C-terminal catalytic Cys residue of the other subunit, or resolving Cys (CR) into an intermolecular disulfide. In the reduced enzyme CP and CR are ~13 Å apart. Therefore, disulfide formation involves an important structural remodeling occurring both at the CP-active site pocket and CR-containing C-terminal domain, which switches the enzyme structure form a fully folded (FF) to a locally unfolded (LU) conformation [17,47]. Based on a series of elegant studies Karplus and coworkers have proposed that the enzyme FF conformation both stabilizes the deprotonated reactive form of CP and provides a steric and electrostatic environment that activates H2O2, hence establishing the observed CP extraordinary high reactivity for H2O2[18,22]. The catalytic intermolecular disulfide is subsequently reduced by thioredoxin, which completes the catalytic cycle, and returns the enzyme to the FF conformation. In eukaryotic enzymes however, the CP-SOH can further react with H2O2 instead of condensing with CR, thus becoming oxidized to the corresponding sulfinic acid (−SO2H), which interrupts the peroxidatic cycle. Hyperoxidized Prx is not a dead-end product; it is reactivated by ATP-dependent reduction of the sulfinate by sulfiredoxin (Srx) [45,6]. The sensitivity of eukaryotic enzymes to hyperoxidation is linked to the presence of two sequence fingerprints absent in other family enzymes, a three amino acids insertion in the loop between α4 and β5 associated with a conserved GGLC motif, and an additional helix (α7) occurring as a C-terminal extension and containing the conserved YF motif [47]. Such a structural configuration is thought to slow down the FF to LU transition rate, thereby favoring hyperoxidation [47].


In vivo parameters influencing 2-Cys Prx oligomerization: The role of enzyme sulfinylation.

Noichri Y, Palais G, Ruby V, D'Autreaux B, Delaunay-Moisan A, Nyström T, Molin M, Toledano MB - Redox Biol (2015)

The peroxidatic cycle of eukaryotic 2-Cys Prxs. Eukaryotic typical 2-Cys Prx are obligate dimers with a mechanism involving two Cys residues, in which CP decomposes H2O2 into H2O by nucleophilic attack and is oxidized to a sulfenic acid (CP-SOH). The sulfenic acid then reacts with the resolving Cys (CR) residue of the other subunit to form an intermolecular disulfide [48]. This disulfide is then reduced by thioredoxin, which completes the catalytic cycle. Alternatively, when H2O2 levels raises, the CP-SOH can further react with H2O2, which leads to formation of a CP-sulfinic acid (CP-SO2H). The latter is reversed back to CP-SOH by ATP-dependent reduction by sulfiredoxin (Srx).
© Copyright Policy - CC BY-NC-ND
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4556779&req=5

f0005: The peroxidatic cycle of eukaryotic 2-Cys Prxs. Eukaryotic typical 2-Cys Prx are obligate dimers with a mechanism involving two Cys residues, in which CP decomposes H2O2 into H2O by nucleophilic attack and is oxidized to a sulfenic acid (CP-SOH). The sulfenic acid then reacts with the resolving Cys (CR) residue of the other subunit to form an intermolecular disulfide [48]. This disulfide is then reduced by thioredoxin, which completes the catalytic cycle. Alternatively, when H2O2 levels raises, the CP-SOH can further react with H2O2, which leads to formation of a CP-sulfinic acid (CP-SO2H). The latter is reversed back to CP-SOH by ATP-dependent reduction by sulfiredoxin (Srx).
Mentions: 2-Cys Prx are obligate head-to-tail B-type homodimers, each with two catalytic Cys residues. In the peroxidatic cycle, the N-terminal Cys, named CP for peroxidatic Cys, reduces H2O2, and is in turn oxidized to a sulfenic acid (CP-SOH) [48] (Fig. 1). The Cys-sulfenic acid moiety then condenses with the C-terminal catalytic Cys residue of the other subunit, or resolving Cys (CR) into an intermolecular disulfide. In the reduced enzyme CP and CR are ~13 Å apart. Therefore, disulfide formation involves an important structural remodeling occurring both at the CP-active site pocket and CR-containing C-terminal domain, which switches the enzyme structure form a fully folded (FF) to a locally unfolded (LU) conformation [17,47]. Based on a series of elegant studies Karplus and coworkers have proposed that the enzyme FF conformation both stabilizes the deprotonated reactive form of CP and provides a steric and electrostatic environment that activates H2O2, hence establishing the observed CP extraordinary high reactivity for H2O2[18,22]. The catalytic intermolecular disulfide is subsequently reduced by thioredoxin, which completes the catalytic cycle, and returns the enzyme to the FF conformation. In eukaryotic enzymes however, the CP-SOH can further react with H2O2 instead of condensing with CR, thus becoming oxidized to the corresponding sulfinic acid (−SO2H), which interrupts the peroxidatic cycle. Hyperoxidized Prx is not a dead-end product; it is reactivated by ATP-dependent reduction of the sulfinate by sulfiredoxin (Srx) [45,6]. The sensitivity of eukaryotic enzymes to hyperoxidation is linked to the presence of two sequence fingerprints absent in other family enzymes, a three amino acids insertion in the loop between α4 and β5 associated with a conserved GGLC motif, and an additional helix (α7) occurring as a C-terminal extension and containing the conserved YF motif [47]. Such a structural configuration is thought to slow down the FF to LU transition rate, thereby favoring hyperoxidation [47].

Bottom Line: The critical molecular event allowing the peroxidase to chaperone switch is thought to be the enzyme assembly into high molecular weight (HMW) structures brought about by enzyme hyperoxidation.How hyperoxidation promotes HMW assembly is not well understood and Prx mutants allowing disentangling its peroxidase and chaperone functions are lacking.Our data confirm the strict causative link between H2O2-induced hyperoxidation and HMW formation/stabilization, also raising the question of whether CP hyperoxidation triggers the assembly of HMW structures by the stacking of decamers, which is the prevalent view of the literature, or rather, the stabilization of preassembled stacked decamers.

View Article: PubMed Central - PubMed

Affiliation: Oxidative Stress and Cancer, IBITECS, SBIGEM, CEA-Saclay, 91191 Gif-sur-Yvette, France.

No MeSH data available.


Related in: MedlinePlus