Peroxiredoxins (Prxs) are a ubiquitous family of antioxidant proteins. They can be divided into three classes: typical 2-Cys, atypical 2-Cys and 1-Cys peroxiredoxins . The peroxidase reaction comprises two steps centred around a redox-active cysteine called the peroxidatic cysteine. All three peroxiredoxin classes have the first step in common, in which the peroxidatic cysteine attacks the peroxide substrate and is oxidized to S-hydroxycysteine (a sulfenic acid) (see {single/111115a::mechanism}). The second step of the peroxidase reaction, the regeneration of cysteine from S-hydroxycysteine, distinguishes the three peroxiredoxin classes. For typical 2-Cys Prxs, in the second step, the peroxidatic S-hydroxycysteine from one subunit is attacked by the 'resolving' cysteine located in the C-terminus of the second subunit, to form an intersubunit disulfide bond, which is then reduced by one of several cell-specific thiol-containing reductants completing the catalytic cycle. In the atypical 2-Cys Prxs, both the peroxidatic cysteine and its resolving cysteine are in the same polypeptide, so their reaction forms an intrachain disulfide bond. The 1-Cys Prxs conserve only the peroxidatic cysteine, so its regeneration involves direct interaction with a reductant molecule. This bacterial peroxiredoxin differs from most other forms by comprising two types of subunits. One subunit (AhpC) is a typical 2-Cys peroxiredoxin. Following the reduction of the substrate, one AhpC subunit forms a disulfide bond with an identical unit. The disulfide bond is reduced by the second type of subunit (AhpF). This second subunit is a flavin-containing protein that uses electrons from NADH to reduce the cysteine residues on the AhpC subunits back to their active state.
proposed mechanism of H2O2 reduction for the AhpC-AhpF complex. binding mechanism in which the C terminus of AhpC wraps around the N-terminal domain, slowing the dissociation rate for an efficient electron transfer process, and a release mechanism mediated by the conformational change of the C terminus of AhpC upon reduction
proposed mechanism of H2O2 reduction for the AhpC-AhpF complex. binding mechanism in which the C terminus of AhpC wraps around the N-terminal domain, slowing the dissociation rate for an efficient electron transfer process, and a release mechanism mediated by the conformational change of the C terminus of AhpC upon reduction
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SYSTEMATIC NAME
IUBMB Comments
NADH:hydroperoxide oxidoreductase
Peroxiredoxins (Prxs) are a ubiquitous family of antioxidant proteins. They can be divided into three classes: typical 2-Cys, atypical 2-Cys and 1-Cys peroxiredoxins [1]. The peroxidase reaction comprises two steps centred around a redox-active cysteine called the peroxidatic cysteine. All three peroxiredoxin classes have the first step in common, in which the peroxidatic cysteine attacks the peroxide substrate and is oxidized to S-hydroxycysteine (a sulfenic acid) (see {single/111115a::mechanism}). The second step of the peroxidase reaction, the regeneration of cysteine from S-hydroxycysteine, distinguishes the three peroxiredoxin classes. For typical 2-Cys Prxs, in the second step, the peroxidatic S-hydroxycysteine from one subunit is attacked by the 'resolving' cysteine located in the C-terminus of the second subunit, to form an intersubunit disulfide bond, which is then reduced by one of several cell-specific thiol-containing reductants completing the catalytic cycle. In the atypical 2-Cys Prxs, both the peroxidatic cysteine and its resolving cysteine are in the same polypeptide, so their reaction forms an intrachain disulfide bond. The 1-Cys Prxs conserve only the peroxidatic cysteine, so its regeneration involves direct interaction with a reductant molecule. This bacterial peroxiredoxin differs from most other forms by comprising two types of subunits. One subunit (AhpC) is a typical 2-Cys peroxiredoxin. Following the reduction of the substrate, one AhpC subunit forms a disulfide bond with an identical unit. The disulfide bond is reduced by the second type of subunit (AhpF). This second subunit is a flavin-containing protein that uses electrons from NADH to reduce the cysteine residues on the AhpC subunits back to their active state.
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CRYSTALLIZATION (Commentary)
ORGANISM
UNIPROT
LITERATURE
hanging-drop vapour diffusion method at 23°C. Crystal structures of both of the subunits of EcAhpR, EcAhpF and EcAhpC, are solved. The EcAhpF structures (2.0 and 2.65 A resolution) reveal an open and elongated conformation, while that of EcAhpC (3.3 A resolution) forms a decameric ring