Glutathionylation of Trypanosomal Thiol Redox Proteins

Melchers, Johannes; Dirdjaja, Natalie; Ruppert, Thomas; Krauth‐Siegel, R. Luise

doi:10.1074/jbc.m608140200

Cited by 37 publications

(31 citation statements)

References 55 publications

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“…45 47 or Cys 95 but not of both residues in the same protein molecule (48). Modification of one cysteine probably interferes sterically with the modification of the second one in accordance with the structural data that also in the reduced form of Px III both cysteines lie in close proximity.…”

Section: Discussionsupporting

confidence: 82%

Structural Basis for a Distinct Catalytic Mechanism in Trypanosoma brucei Tryparedoxin Peroxidase

Melchers

Diechtierow

Fehér

et al. 2008

Journal of Biological Chemistry

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Trypanosoma brucei, the causative agent of African sleeping sickness, encodes three cysteine homologues (Px I-III) of classical selenocysteine-containing glutathione peroxidases. The enzymes obtain their reducing equivalents from the unique trypanothione (bis(glutathionyl)spermidine)/tryparedoxin system. During catalysis, these tryparedoxin peroxidases cycle between an oxidized form with an intramolecular disulfide bond between Cys 47 and Cys 95 and the reduced peroxidase with both residues in the thiol state. Here we report on the three-dimensional structures of oxidized T. brucei Px III at 1.4 Å resolution obtained by x-ray crystallography and of both the oxidized and the reduced protein determined by NMR spectroscopy. Px III is a monomeric protein unlike the homologous poplar thioredoxin peroxidase (TxP). Trypanosomes and Leishmania, the causative agents of several tropical diseases, have a unique thiol redox metabolism that is based on trypanothione (N 1 ,N 8 -bis(glutathionyl)spermidine) and the flavoenzyme trypanothione reductase (for reviews, see Refs. 1 and 2). The parasites lack catalases and selenocysteine-containing glutathione peroxidases. 2-Cys-peroxiredoxins and cysteine-containing glutathione peroxidasetype enzymes are responsible for hydroperoxide reduction acting both as tryparedoxin peroxidases (for a recent review, see Ref.3). With NADPH as primary electron source, the reducing equivalents flow via trypanothione and tryparedoxin (Tpx), 2 a distant relative of the thioredoxin protein family, onto the peroxidases which then reduce the hydroperoxide substrates (Scheme 1). In Trypanosoma brucei, the causative agent of African sleeping sickness, both the cytosolic 2-Cys peroxiredoxin and the glutathione peroxidase-type enzymes proved to be essential (4, 5).Classical glutathione peroxidases (GPXs) are selenoproteins. Five distinct enzymes have been characterized in mammals, cytosolic GPX1, gastro-intestinal GPX2, plasma GPX3, phospholipid hydroperoxide peroxidase GPX4, and in humans, GPX6, which is restricted to the olfactory system (6). The high specificity of GPX1 for glutathione as reducing substrate gave the protein family its name (7). In the epididymis of rodents and monkeys, a GPX5 is expressed that contains an active site cysteine instead of the selenocysteine. Recently the structure of human GPX7, also a cysteine homologue, has been solved (PDB code 2P31). Expression of this gene is dramatically down-regulated in breast cancer cells (8). In general, cysteine-containing glutathione peroxidase-type enzymes are widespread in nature, and most of the enzymes, few of which are biochemically characterized, function as thioredoxin peroxidases (for reviews, see Refs. 9 and 10).The selenoenzymes contain a catalytic triad. The selenoate of the peroxidatic selenocysteine is supposed to be stabilized by hydrogen bonds with a Gln and a Trp residue (11, 12). Site-directed mutagenesis (13) and computational studies (14, 15) supported the crucial role of the Gln and Trp residue for catalysis. Both residues ...

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Section: Discussionsupporting

confidence: 82%

Structural Basis for a Distinct Catalytic Mechanism in Trypanosoma brucei Tryparedoxin Peroxidase

Melchers

Diechtierow

Fehér

et al. 2008

Journal of Biological Chemistry

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“…Protein (de)glutathionylation is a reversible regulatory mechanism in which Grxs play a pivotal role (5,6). Previously, we demonstrated that several thiol redox proteins of T. brucei are susceptible to specific glutathionylation in vitro (59). As shown here, both parasite Grxs catalyze the reduction of GSH mixed disulfides of BSA, TXNPx, or 2-mercaptoethanol.…”

Section: Table 2 Reduction Of Glutathionylated Model Substrates By DIsupporting

confidence: 68%

The Dithiol Glutaredoxins of African Trypanosomes Have Distinct Roles and Are Closely Linked to the Unique Trypanothione Metabolism

Ceylan

Seidel

Ziebart

et al. 2010

Journal of Biological Chemistry

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“…2A). In contrast to the specificity displayed by E. coli Grx4 and S. cerevisiae Grx5, Cys181-not Cys104-forms a mixed disulfide with GSH and Gsp (58), which can trigger the formation of an intramolecular Cys104-Cys181 disulfide bridge (16,58). In vitro, both oxidation states are reduced by TXN or the T(SH) 2 /TR system (27,58).…”

Section: Oligomeric State and Redox Properties Of The T Brucei 1-c-grxsmentioning

confidence: 96%

“…An N-terminal region of about *37 residues, exclusive of the kinetoplastid 1-C-Grx1s, has recently been identified to be responsible for dimerization of the T. brucei and T. cruzi proteins (55a). In vitro, T. brucei 1-CGrx1 lacks any general thiol-disulfide oxidoreductase activity (27) but is susceptible to oxidation by GSSG and Gsp disulfide (16,58). In addition to the active site Cys104, T. brucei 1-CGrx1 contains a second cysteine, namely Cys181, located at the fourth position from the C-terminus ( Fig.…”

Section: Oligomeric State and Redox Properties Of The T Brucei 1-c-grxsmentioning

confidence: 99%

“…At the fourth position form the C-terminus Cys181 is located ( Figs. 2A and 5A) which in vitro can form an intramolecular disulfide with the active-site Cys104 (58). In the available structure the two residues are positioned at a distance far beyond that required for a disulfide bridge, and only a substantial conformational change or a local unfolding would allow formation of this covalent link.…”

Section: Structural Basis For Monothiol Glutaredoxin Functionmentioning

confidence: 99%

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Mono- and Dithiol Glutaredoxins in the Trypanothione-Based Redox Metabolism of Pathogenic Trypanosomes

Comini

Krauth‐Siegel²,

Bellanda³

2013

Antioxidants & Redox Signaling

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Significance: Glutaredoxins are ubiquitous small thiol proteins of the thioredoxin-fold superfamily. Two major groups are distinguished based on their active sites: the dithiol (2-C-Grxs) and the monothiol (1-C-Grxs) glutaredoxins with a CXXC and a CXXS active site motif, respectively. Glutaredoxins are involved in cellular redox and/or iron sulfur metabolism. Usually their functions are closely linked to the glutathione system. Trypanosomatids, the causative agents of several tropical diseases, rely on trypanothione as principal low molecular mass thiol, and their glutaredoxins readily react with the unique bis(glutathionyl) spermidine conjugate.

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Glutathionylation of Trypanosomal Thiol Redox Proteins

Cited by 37 publications

References 55 publications

Structural Basis for a Distinct Catalytic Mechanism in Trypanosoma brucei Tryparedoxin Peroxidase

Structural Basis for a Distinct Catalytic Mechanism in Trypanosoma brucei Tryparedoxin Peroxidase

The Dithiol Glutaredoxins of African Trypanosomes Have Distinct Roles and Are Closely Linked to the Unique Trypanothione Metabolism

Mono- and Dithiol Glutaredoxins in the Trypanothione-Based Redox Metabolism of Pathogenic Trypanosomes

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