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Li TT, Zhao DY, Liang QL, Elsheikha HM, Wang M, Sun LX, Zhang ZW, Chen XQ, Zhu XQ, Wang JL. The antioxidant protein glutaredoxin 1 is essential for oxidative stress response and pathogenicity of Toxoplasma gondii. FASEB J 2023; 37:e22932. [PMID: 37115746 DOI: 10.1096/fj.202201275r] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2022] [Revised: 03/22/2023] [Accepted: 04/07/2023] [Indexed: 04/29/2023]
Abstract
Glutaredoxins (Grxs) are ubiquitous antioxidant proteins involved in many molecular processes to protect cells against oxidative damage. Here, we study the roles of Grxs in the pathogenicity of Toxoplasma gondii. We show that Grxs are localized in the mitochondria (Grx1), cytoplasm (Grx2), and apicoplast (Grx3, Grx4), while Grx5 had an undetectable level of expression. We generated Δgrx1-5 mutants of T. gondii type I RH and type II Pru strains using CRISPR-Cas9 system. No significant differences in the infectivity were detected between four Δgrx (grx2-grx5) strains and their respective wild-type (WT) strains in vitro or in vivo. Additionally, no differences were detected in the production of reactive oxygen species, total antioxidant capacity, superoxide dismutase activity, and sensitivity to external oxidative stimuli. Interestingly, RHΔgrx1 or PruΔgrx1 exhibited significant differences in all the investigated aspects compared to the other grx2-grx5 mutant and WT strains. Transcriptome analysis suggests that deletion of grx1 altered the expression of genes involved in transport and metabolic pathways, signal transduction, translation, and obsolete oxidation-reduction process. The data support the conclusion that grx1 supports T. gondii resistance to oxidative killing and is essential for the parasite growth in cultured cells and pathogenicity in mice and that the active site CGFS motif was necessary for Grx1 activity.
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Affiliation(s)
- Ting-Ting Li
- State Key Laboratory for Animal Disease Control and Prevention, Key Laboratory of Veterinary Parasitology of Gansu Province, Lanzhou Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Gansu Province, Lanzhou, People's Republic of China
- Institute of Urban Agriculture, Chinese Academy of Agricultural Sciences, Sichuan Province, Chengdu, People's Republic of China
| | - Dan-Yu Zhao
- State Key Laboratory for Animal Disease Control and Prevention, Key Laboratory of Veterinary Parasitology of Gansu Province, Lanzhou Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Gansu Province, Lanzhou, People's Republic of China
| | - Qin-Li Liang
- State Key Laboratory for Animal Disease Control and Prevention, Key Laboratory of Veterinary Parasitology of Gansu Province, Lanzhou Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Gansu Province, Lanzhou, People's Republic of China
| | - Hany M Elsheikha
- Faculty of Medicine and Health Sciences, School of Veterinary Medicine and Science, University of Nottingham, Loughborough, UK
| | - Meng Wang
- State Key Laboratory for Animal Disease Control and Prevention, Key Laboratory of Veterinary Parasitology of Gansu Province, Lanzhou Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Gansu Province, Lanzhou, People's Republic of China
- Institute of Urban Agriculture, Chinese Academy of Agricultural Sciences, Sichuan Province, Chengdu, People's Republic of China
| | - Li-Xiu Sun
- State Key Laboratory for Animal Disease Control and Prevention, Key Laboratory of Veterinary Parasitology of Gansu Province, Lanzhou Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Gansu Province, Lanzhou, People's Republic of China
| | - Zhi-Wei Zhang
- State Key Laboratory for Animal Disease Control and Prevention, Key Laboratory of Veterinary Parasitology of Gansu Province, Lanzhou Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Gansu Province, Lanzhou, People's Republic of China
| | - Xiao-Qing Chen
- Jiangxi Provincial Key Laboratory for Animal Health, College of Animal Science and Technology, Jiangxi Agricultural University, Nanchang, Jiangxi Province, People's Republic of China
| | - Xing-Quan Zhu
- Laboratory of Parasitic Diseases, College of Veterinary Medicine, Shanxi Agricultural University, Taigu, Shanxi Province, People's Republic of China
- Key Laboratory of Veterinary Public Health of Yunnan Province, College of Veterinary Medicine, Yunnan Agricultural University, Kunming, Yunnan Province, People's Republic of China
| | - Jin-Lei Wang
- State Key Laboratory for Animal Disease Control and Prevention, Key Laboratory of Veterinary Parasitology of Gansu Province, Lanzhou Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Gansu Province, Lanzhou, People's Republic of China
- Institute of Urban Agriculture, Chinese Academy of Agricultural Sciences, Sichuan Province, Chengdu, People's Republic of China
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Tiwari S, Sharma N, Sharma GP, Mishra N. Redox interactome in malaria parasite Plasmodium falciparum. Parasitol Res 2021; 120:423-434. [PMID: 33459846 DOI: 10.1007/s00436-021-07051-9] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2020] [Accepted: 01/08/2021] [Indexed: 11/26/2022]
Abstract
The malaria-causing parasite Plasmodium falciparum is a severe threat to human health across the globe. This parasite alone causes the highest morbidity and mortality than any other species of Plasmodium. The parasites dynamically multiply in the erythrocytes of the vertebrate hosts, a large number of reactive oxygen species that damage biological macromolecules are produced in the cell during parasite growth. To relieve this intense oxidative stress, the parasite employs an NADPH-dependent thioredoxin and glutathione system that acts as an antioxidant and maintains redox status in the parasite. The mutual interaction of both redox proteins is involved in various biological functions and the survival of the erythrocytic stage of the parasite. Since the Plasmodium species is deficient in catalase and classical glutathione peroxidase, so their redox balance relies on a complex set of five peroxiredoxins, differentially positioned in the cytosol, mitochondria, apicoplast, and nucleus with partly overlapping substrate preferences. Moreover, Plasmodium falciparum possesses a set of members belonging to the thioredoxin superfamily, such as three thioredoxins, two thioredoxin-like proteins, one dithiol, three monocysteine glutaredoxins, and one redox-active plasmoredoxin with largely redundant functions. This review paper aims to discuss and encapsulate the biological function and current knowledge of the functional redox network of Plasmodium falciparum.
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Affiliation(s)
- Savitri Tiwari
- Parasite-Host Biology Group, National Institute of Malaria Research, Indian Council of Medical Research, Sector-8, Dwarka, New Delhi, 110077, India
| | - Nivedita Sharma
- Parasite-Host Biology Group, National Institute of Malaria Research, Indian Council of Medical Research, Sector-8, Dwarka, New Delhi, 110077, India
| | | | - Neelima Mishra
- Parasite-Host Biology Group, National Institute of Malaria Research, Indian Council of Medical Research, Sector-8, Dwarka, New Delhi, 110077, India.
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Quantitative assessment of the determinant structural differences between redox-active and inactive glutaredoxins. Nat Commun 2020; 11:1725. [PMID: 32265442 PMCID: PMC7138851 DOI: 10.1038/s41467-020-15441-3] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2019] [Accepted: 03/04/2020] [Indexed: 11/08/2022] Open
Abstract
Class I glutaredoxins are enzymatically active, glutathione-dependent oxidoreductases, whilst class II glutaredoxins are typically enzymatically inactive, Fe-S cluster-binding proteins. Enzymatically active glutaredoxins harbor both a glutathione-scaffold site for reacting with glutathionylated disulfide substrates and a glutathione-activator site for reacting with reduced glutathione. Here, using yeast ScGrx7 as a model protein, we comprehensively identified and characterized key residues from four distinct protein regions, as well as the covalently bound glutathione moiety, and quantified their contribution to both interaction sites. Additionally, we developed a redox-sensitive GFP2-based assay, which allowed the real-time assessment of glutaredoxin structure-function relationships inside living cells. Finally, we employed this assay to rapidly screen multiple glutaredoxin mutants, ultimately enabling us to convert enzymatically active and inactive glutaredoxins into each other. In summary, we have gained a comprehensive understanding of the mechanistic underpinnings of glutaredoxin catalysis and have elucidated the determinant structural differences between the two main classes of glutaredoxins. Glutaredoxins play a central role in numerous biological processes including cellular redox homeostasis and Fe-S cluster biogenesis. Here the authors establish the molecular basis for glutaredoxin redox catalysis through comprehensive biochemical and structural analyses.
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Kumar A, Chauhan N, Singh S. Understanding the Cross-Talk of Redox Metabolism and Fe-S Cluster Biogenesis in Leishmania Through Systems Biology Approach. Front Cell Infect Microbiol 2019; 9:15. [PMID: 30778378 PMCID: PMC6369582 DOI: 10.3389/fcimb.2019.00015] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2018] [Accepted: 01/17/2019] [Indexed: 11/13/2022] Open
Abstract
Leishmania parasites possess an exceptional oxidant and chemical defense mechanism, involving a very unique small molecular weight thiol, trypanothione (T[SH]2), that helps the parasite to manage its survival inside the host macrophage. The reduced state of T[SH]2 is maintained by NADPH-dependent trypanothione reductase (TryR) by recycling trypanothione disulfide (TS2). Along with its most important role as central reductant, T[SH]2 have also been assumed to regulate the activation of iron-sulfur cluster proteins (Fe/S). Fe/S clusters are versatile cofactors of various proteins and execute a much broader range of essential biological processes viz., TCA cycle, redox homeostasis, etc. Although, several Fe/S cluster proteins and their roles have been identified in Leishmania, some of the components of how T[SH]2 is involved in the regulation of Fe/S proteins remains to be explored. In pursuit of this aim, a systems biology approach was undertaken to get an insight into the overall picture to unravel how T[SH]2 synthesis and reduction is linked with the regulation of Fe/S cluster proteins and controls the redox homeostasis at a larger scale. In the current study, we constructed an in silico kinetic model of T[SH]2 metabolism. T[SH]2 reduction reaction was introduced with a perturbation in the form of its inhibition to predict the overall behavior of the model. The main control of reaction fluxes were exerted by TryR reaction rate that affected almost all the important reactions in the model. It was observed that the model was more sensitive to the perturbation introduced in TryR reaction, 5 to 6-fold. Furthermore, due to inhibition, the T[SH]2 synthesis rate was observed to be gradually decreased by 8 to 14-fold. This has also caused an elevated level of free radicals which apparently affected the activation of Fe/S cluster proteins. The present kinetic model has demonstrated the importance of T[SH]2 in leishmanial cellular redox metabolism. Hence, we suggest that, by designing highly potent and specific inhibitors of TryR enzyme, inhibition of T[SH]2 reduction and overall inhibition of most of the downstream pathways including Fe/S protein activation reactions, can be accomplished.
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Abstract
SIGNIFICANCE Glutathione metabolism is comparable to a jigsaw puzzle with too many pieces. It is supposed to comprise (i) the reduction of disulfides, hydroperoxides, sulfenic acids, and nitrosothiols, (ii) the detoxification of aldehydes, xenobiotics, and heavy metals, and (iii) the synthesis of eicosanoids, steroids, and iron-sulfur clusters. In addition, glutathione affects oxidative protein folding and redox signaling. Here, I try to provide an overview on the relevance of glutathione-dependent pathways with an emphasis on quantitative data. Recent Advances: Intracellular redox measurements reveal that the cytosol, the nucleus, and mitochondria contain very little glutathione disulfide and that oxidative challenges are rapidly counterbalanced. Genetic approaches suggest that iron metabolism is the centerpiece of the glutathione puzzle in yeast. Furthermore, recent biochemical studies provide novel insights on glutathione transport processes and uncoupling mechanisms. CRITICAL ISSUES Which parts of the glutathione puzzle are most relevant? Does this explain the high intracellular concentrations of reduced glutathione? How can iron-sulfur cluster biogenesis, oxidative protein folding, or redox signaling occur at high glutathione concentrations? Answers to these questions not only seem to depend on the organism, cell type, and subcellular compartment but also on different ideologies among researchers. FUTURE DIRECTIONS A rational approach to compare the relevance of glutathione-dependent pathways is to combine genetic and quantitative kinetic data. However, there are still many missing pieces and too little is known about the compartment-specific repertoire and concentration of numerous metabolites, substrates, enzymes, and transporters as well as rate constants and enzyme kinetic patterns. Gathering this information might require the development of novel tools but is crucial to address potential kinetic competitions and to decipher uncoupling mechanisms to solve the glutathione puzzle. Antioxid. Redox Signal. 27, 1130-1161.
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Affiliation(s)
- Marcel Deponte
- Department of Parasitology, Ruprecht-Karls University , Heidelberg, Germany
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Glutaredoxin catalysis requires two distinct glutathione interaction sites. Nat Commun 2017; 8:14835. [PMID: 28374771 PMCID: PMC5382279 DOI: 10.1038/ncomms14835] [Citation(s) in RCA: 70] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2016] [Accepted: 02/02/2017] [Indexed: 01/15/2023] Open
Abstract
Glutaredoxins are key players in cellular redox homoeostasis and exert a variety of essential functions ranging from glutathione-dependent catalysis to iron metabolism. The exact structure–function relationships and mechanistic differences among glutaredoxins that are active or inactive in standard enzyme assays have so far remained elusive despite numerous kinetic and structural studies. Here, we elucidate the enzymatic mechanism showing that glutaredoxins require two distinct glutathione interaction sites for efficient redox catalysis. The first site interacts with the glutathione moiety of glutathionylated disulfide substrates. The second site activates glutathione as the reducing agent. We propose that the requirement of two distinct glutathione interaction sites for the efficient reduction of glutathionylated disulfide substrates explains the deviating structure–function relationships, activities and substrate preferences of different glutaredoxin subfamilies as well as thioredoxins. Our model also provides crucial insights for the design or optimization of artificial glutaredoxins, transition-state inhibitors and glutaredoxin-coupled redox sensors. Glutaredoxins have important roles in redox processes. Here the authors show that the enzymatic activity of glutaredoxins requires two distinct glutathione interactions sites, one recognizing the glutathione disulfide substrate and one activating glutathione as a reducing agent.
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Role and Regulation of Glutathione Metabolism in Plasmodium falciparum. Molecules 2015; 20:10511-34. [PMID: 26060916 PMCID: PMC6272303 DOI: 10.3390/molecules200610511] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2015] [Revised: 05/11/2015] [Accepted: 06/01/2015] [Indexed: 11/30/2022] Open
Abstract
Malaria in humans is caused by one of five species of obligate intracellular protozoan parasites of the genus Plasmodium. P. falciparum causes the most severe disease and is responsible for 600,000 deaths annually, primarily in Sub-Saharan Africa. It has long been suggested that during their development, malaria parasites are exposed to environmental and metabolic stresses. One strategy to drug discovery was to increase these stresses by interfering with the parasites’ antioxidant and redox systems, which may be a valuable approach to disease intervention. Plasmodium possesses two redox systems—the thioredoxin and the glutathione system—with overlapping but also distinct functions. Glutathione is the most abundant low molecular weight redox active thiol in the parasites existing primarily in its reduced form representing an excellent thiol redox buffer. This allows for an efficient maintenance of the intracellular reducing environment of the parasite cytoplasm and its organelles. This review will highlight the mechanisms that are responsible for sustaining an adequate concentration of glutathione and maintaining its redox state in Plasmodium. It will provide a summary of the functions of the tripeptide and will discuss the potential of glutathione metabolism for drug discovery against human malaria parasites.
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Begas P, Staudacher V, Deponte M. Systematic re-evaluation of the bis(2-hydroxyethyl)disulfide (HEDS) assay reveals an alternative mechanism and activity of glutaredoxins. Chem Sci 2015; 6:3788-3796. [PMID: 29218148 PMCID: PMC5707495 DOI: 10.1039/c5sc01051a] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2015] [Accepted: 05/07/2015] [Indexed: 11/21/2022] Open
Abstract
The sequential kinetic patterns of mono- and dithiol glutaredoxins in the HEDS assay reflect an alternative enzymatic mechanism for the glutathione-dependent reduction of disulfide substrates.
The reduction of bis(2-hydroxyethyl)disulfide (HEDS) by reduced glutathione (GSH) is the most commonly used assay to analyze the presence and properties of enzymatically active glutaredoxins (Grx), a family of central redox proteins in eukaryotes and glutathione-utilizing prokaryotes. Enzymatically active Grx usually prefer glutathionylated disulfide substrates. These are converted via a ping-pong mechanism. Sequential kinetic patterns for the HEDS assay have therefore been puzzling since 1991. Here we established a novel assay and used the model enzyme ScGrx7 from yeast and PfGrx from Plasmodium falciparum to test several possible causes for the sequential kinetics such as pre-enzymatic GSH depletion, simultaneous binding of a glutathionylated substrate and GSH, as well as substrate or product inhibition. Furthermore, we analyzed the non-enzymatic reaction between HEDS and GSH by HPLC and mass spectrometry suggesting that such a reaction is too slow to explain high Grx activities in the assay. The most plausible interpretation of our results is a direct Grx-catalyzed reduction of HEDS. Physiological implications of this alternative mechanism and of the Grx-catalyzed reduction of non-glutathione disulfide substrates are discussed.
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Affiliation(s)
- Patricia Begas
- Department of Parasitology , Ruprecht-Karls University , D-69120 Heidelberg , Germany .
| | - Verena Staudacher
- Department of Parasitology , Ruprecht-Karls University , D-69120 Heidelberg , Germany .
| | - Marcel Deponte
- Department of Parasitology , Ruprecht-Karls University , D-69120 Heidelberg , Germany .
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Prakash K, Goyal M, Soni A, Siddiqui AJ, Bhardwaj J, Puri SK. Molecular cloning and biochemical characterization of iron superoxide dismutase from the rodent malaria parasite Plasmodium vinckei. Parasitol Int 2014; 63:817-25. [DOI: 10.1016/j.parint.2014.07.004] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2014] [Revised: 07/11/2014] [Accepted: 07/16/2014] [Indexed: 10/24/2022]
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Comini MA, Krauth-Siegel RL, Bellanda M. Mono- and dithiol glutaredoxins in the trypanothione-based redox metabolism of pathogenic trypanosomes. Antioxid Redox Signal 2013; 19:708-22. [PMID: 22978520 PMCID: PMC3739957 DOI: 10.1089/ars.2012.4932] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
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. RECENT ADVANCES Two 2-C-Grxs and three 1-C-Grxs have been identified in pathogenic trypanosomatids. The 2-C-Grxs catalyze the reduction of glutathione disulfide by trypanothione and display reductase activity towards protein disulfides, as well as protein-glutathione mixed disulfides. In vitro, all three 1-C-Grxs as well as the cytosolic 2-C-Grx of Trypanosoma brucei can complex an iron-sulfur cluster. Recently the structure of the 1-C-Grx1 has been solved by NMR spectroscopy. The structure is very similar to those of other 1-C-Grxs, with some differences in the loop containing the conserved cis-Pro and the surface charge distribution. CRITICAL ISSUES Although four of the five trypanosomal glutaredoxins proved to coordinate an iron-sulfur cluster in vitro, the physiological role of the mitochondrial and cytosolic proteins, respectively, has only started to be unraveled. FUTURE DIRECTIONS The use of trypanothione by the glutaredoxins has established a novel role for this parasite-specific dithiol. Future work should reveal if these differences can be exploited for the development of novel antiparasitic drugs.
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Affiliation(s)
- Marcelo A Comini
- Laboratory Redox Biology of Trypanosomes, Institut Pasteur de Montevideo, Montevideo, Uruguay.
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Djuika CF, Fiedler S, Schnölzer M, Sanchez C, Lanzer M, Deponte M. Plasmodium falciparum antioxidant protein as a model enzyme for a special class of glutaredoxin/glutathione-dependent peroxiredoxins. Biochim Biophys Acta Gen Subj 2013; 1830:4073-90. [DOI: 10.1016/j.bbagen.2013.04.020] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2013] [Revised: 04/15/2013] [Accepted: 04/16/2013] [Indexed: 01/06/2023]
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Trypanothione: A unique bis-glutathionyl derivative in trypanosomatids. Biochim Biophys Acta Gen Subj 2013; 1830:3199-216. [DOI: 10.1016/j.bbagen.2013.01.013] [Citation(s) in RCA: 84] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2012] [Revised: 01/11/2013] [Accepted: 01/16/2013] [Indexed: 11/21/2022]
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Deponte M. Glutathione catalysis and the reaction mechanisms of glutathione-dependent enzymes. Biochim Biophys Acta Gen Subj 2013; 1830:3217-66. [DOI: 10.1016/j.bbagen.2012.09.018] [Citation(s) in RCA: 625] [Impact Index Per Article: 56.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2012] [Accepted: 09/25/2012] [Indexed: 12/12/2022]
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The antimalarial activities of methylene blue and the 1,4-naphthoquinone 3-[4-(trifluoromethyl)benzyl]-menadione are not due to inhibition of the mitochondrial electron transport chain. Antimicrob Agents Chemother 2013; 57:2114-20. [PMID: 23439633 DOI: 10.1128/aac.02248-12] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Methylene blue and a series of recently developed 1,4-naphthoquinones, including 3-[4-(substituted)benzyl]-menadiones, are potent antimalarial agents in vitro and in vivo. The activity of these structurally diverse compounds against the human malaria parasite Plasmodium falciparum might involve their peculiar redox properties. According to the current theory, redox-active methylene blue and 3-[4-(trifluoromethyl)benzyl]-menadione are "subversive substrates." These agents are thought to shuttle electrons from reduced flavoproteins to acceptors such as hemoglobin-associated or free Fe(III)-protoporphyrin IX. The reduction of Fe(III)-protoporphyrin IX could subsequently prevent essential hemoglobin digestion and heme detoxification in the parasite. Alternatively, owing to their structures and redox properties, methylene blue and 1,4-naphthoquinones might also affect the mitochondrial electron transport chain. Here, we tested the latter hypothesis using an established system of transgenic P. falciparum cell lines and the antimalarial agents atovaquone and chloroquine as controls. In contrast to atovaquone, methylene blue and 3-[4-(trifluoromethyl)benzyl]-menadione do not inhibit the mitochondrial electron transport chain. A systematic comparison of the morphologies of drug-treated parasites furthermore suggests that the three drugs do not share a mechanism of action. Our findings support the idea that methylene blue and 3-[4-(trifluoromethyl)benzyl]-menadione exert their antimalarial activity as redox-active subversive substrates.
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Kehr S, Sturm N, Rahlfs S, Przyborski JM, Becker K. Compartmentation of redox metabolism in malaria parasites. PLoS Pathog 2010; 6:e1001242. [PMID: 21203490 PMCID: PMC3009606 DOI: 10.1371/journal.ppat.1001242] [Citation(s) in RCA: 129] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2010] [Accepted: 11/23/2010] [Indexed: 01/06/2023] Open
Abstract
Malaria, caused by the apicomplexan parasite Plasmodium, still represents a major threat to human health and welfare and leads to about one million human deaths annually. Plasmodium is a rapidly multiplying unicellular organism undergoing a complex developmental cycle in man and mosquito – a life style that requires rapid adaptation to various environments. In order to deal with high fluxes of reactive oxygen species and maintain redox regulatory processes and pathogenicity, Plasmodium depends upon an adequate redox balance. By systematically studying the subcellular localization of the major antioxidant and redox regulatory proteins, we obtained the first complete map of redox compartmentation in Plasmodium falciparum. We demonstrate the targeting of two plasmodial peroxiredoxins and a putative glyoxalase system to the apicoplast, a non-photosynthetic plastid. We furthermore obtained a complete picture of the compartmentation of thioredoxin- and glutaredoxin-like proteins. Notably, for the two major antioxidant redox-enzymes – glutathione reductase and thioredoxin reductase – Plasmodium makes use of alternative-translation-initiation (ATI) to achieve differential targeting. Dual localization of proteins effected by ATI is likely to occur also in other Apicomplexa and might open new avenues for therapeutic intervention. The unicellular parasite Plasmodium falciparum is the causative agent of tropical malaria, which represents a global health burden. In order to survive in its human host and the malaria vector Anopheles, malaria parasites depend on adequate antioxidant defense and efficient redox regulation. Furthermore, as shown by glucose-6 phosphate dehydrogenase deficiency, a genetic variation protecting from malaria, redox equilibrium plays a vital role in parasite pathogenicity. Using a green fluorescent protein reporter gene, we systematically studied the subcellular compartmentation of redox networks in Plasmodium falciparum. Based on our results and data from literature, we provide the first thorough map of redox compartmentation. Most interestingly, for the two major antioxidant redox-enzymes – glutathione reductase (GR) and thioredoxin reductase (TrxR) – Plasmodium falciparum makes use of alternative translation initiation to translate protein isoforms with differing subcellular localization from one gene. Dual localization of proteins due to alternative translation initiation might occur frequently in Apicomplexa and identification of further genes that have evolved alternative translation initiation is likely to offer new therapeutic strategies against this devastating disease.
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Affiliation(s)
- Sebastian Kehr
- Interdisciplinary Research Centre, Justus Liebig University, Giessen, Germany
| | - Nicole Sturm
- Interdisciplinary Research Centre, Justus Liebig University, Giessen, Germany
| | - Stefan Rahlfs
- Interdisciplinary Research Centre, Justus Liebig University, Giessen, Germany
| | - Jude M. Przyborski
- Department of Parasitology, Faculty of Biology, Philipps University Marburg, Marburg, Germany
| | - Katja Becker
- Interdisciplinary Research Centre, Justus Liebig University, Giessen, Germany
- * E-mail:
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Li L, Cheng N, Hirschi KD, Wang X. Structure of Arabidopsis chloroplastic monothiol glutaredoxin AtGRXcp. ACTA CRYSTALLOGRAPHICA SECTION D: BIOLOGICAL CRYSTALLOGRAPHY 2010; 66:725-32. [PMID: 20516625 PMCID: PMC2879357 DOI: 10.1107/s0907444910013119] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/08/2010] [Accepted: 04/08/2010] [Indexed: 01/13/2023]
Abstract
The structure of Arabidopsis monothiol glutaredoxin AtGRXcp has been determined and reveals unique structural features of monothiol glutaredoxins, key residues for their interaction with glutathione and structural determinants for their distinct biochemical properties. Monothiol glutaredoxins (Grxs) play important roles in maintaining redox homeostasis in living cells and are conserved across species. Arabidopsis thaliana monothiol glutaredoxin AtGRXcp is critical for protection from oxidative stress in chloroplasts. The crystal structure of AtGRXcp has been determined at 2.4 Å resolution. AtGRXcp has a glutaredoxin/thioredoxin-like fold with distinct structural features that differ from those of dithiol Grxs. The structure reveals that the putative active-site motif CGFS is well defined and is located on the molecular surface and that a long groove extends to both sides of the catalytic Cys97. Structural comparison and molecular modeling suggest that glutathione can bind in this groove and form extensive interactions with conserved charged residues including Lys89, Arg126 and Asp152. Further comparative studies reveal that a unique loop with five additional residues adjacent to the active-site motif may be a key structural feature of monothiol Grxs and may influence their function. This study provides the first structural information on plant CGFS-type monothiol Grxs, allowing a better understanding of the redox-regulation mechanism mediated by these plant Grxs.
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Affiliation(s)
- Lenong Li
- Plant Biology Division, Samuel Roberts Noble Foundation, 2510 Sam Noble Parkway, Ardmore, Oklahoma 73401, USA
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Gao XH, Zaffagnini M, Bedhomme M, Michelet L, Cassier-Chauvat C, Decottignies P, Lemaire SD. Biochemical characterization of glutaredoxins fromChlamydomonas reinhardtii: Kinetics and specificity in deglutathionylation reactions. FEBS Lett 2010; 584:2242-8. [DOI: 10.1016/j.febslet.2010.04.034] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2010] [Revised: 04/09/2010] [Accepted: 04/12/2010] [Indexed: 10/19/2022]
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Eckers E, Bien M, Stroobant V, Herrmann JM, Deponte M. Biochemical Characterization of Dithiol Glutaredoxin 8 from Saccharomyces cerevisiae: The Catalytic Redox Mechanism Redux. Biochemistry 2009; 48:1410-23. [DOI: 10.1021/bi801859b] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Affiliation(s)
- Elisabeth Eckers
- Butenandt Institute for Physiological Chemistry, Ludwig-Maximilians University, D-81377 Munich, Germany, Cell Biology, University of Kaiserslautern, D-67663 Kaiserslautern, Germany, and Ludwig Institute for Cancer Research and Cellular Genetics Unit, Université Catholique de Louvain, B-1200 Brussels, Belgium
| | - Melanie Bien
- Butenandt Institute for Physiological Chemistry, Ludwig-Maximilians University, D-81377 Munich, Germany, Cell Biology, University of Kaiserslautern, D-67663 Kaiserslautern, Germany, and Ludwig Institute for Cancer Research and Cellular Genetics Unit, Université Catholique de Louvain, B-1200 Brussels, Belgium
| | - Vincent Stroobant
- Butenandt Institute for Physiological Chemistry, Ludwig-Maximilians University, D-81377 Munich, Germany, Cell Biology, University of Kaiserslautern, D-67663 Kaiserslautern, Germany, and Ludwig Institute for Cancer Research and Cellular Genetics Unit, Université Catholique de Louvain, B-1200 Brussels, Belgium
| | - Johannes M. Herrmann
- Butenandt Institute for Physiological Chemistry, Ludwig-Maximilians University, D-81377 Munich, Germany, Cell Biology, University of Kaiserslautern, D-67663 Kaiserslautern, Germany, and Ludwig Institute for Cancer Research and Cellular Genetics Unit, Université Catholique de Louvain, B-1200 Brussels, Belgium
| | - Marcel Deponte
- Butenandt Institute for Physiological Chemistry, Ludwig-Maximilians University, D-81377 Munich, Germany, Cell Biology, University of Kaiserslautern, D-67663 Kaiserslautern, Germany, and Ludwig Institute for Cancer Research and Cellular Genetics Unit, Université Catholique de Louvain, B-1200 Brussels, Belgium
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20
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Comini MA, Rettig J, Dirdjaja N, Hanschmann EM, Berndt C, Krauth-Siegel RL. Monothiol Glutaredoxin-1 Is an Essential Iron-Sulfur Protein in the Mitochondrion of African Trypanosomes. J Biol Chem 2008; 283:27785-27798. [DOI: 10.1074/jbc.m802010200] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
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21
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Tripathi T, Rahlfs S, Becker K, Bhakuni V. Structural and stability characteristics of a monothiol glutaredoxin: Glutaredoxin-like protein 1 from Plasmodium falciparum. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2008; 1784:946-52. [DOI: 10.1016/j.bbapap.2008.03.012] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/10/2008] [Revised: 03/26/2008] [Accepted: 03/28/2008] [Indexed: 01/16/2023]
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22
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Mesecke N, Spang A, Deponte M, Herrmann JM. A novel group of glutaredoxins in the cis-Golgi critical for oxidative stress resistance. Mol Biol Cell 2008; 19:2673-80. [PMID: 18400945 PMCID: PMC2397307 DOI: 10.1091/mbc.e07-09-0896] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2007] [Revised: 03/25/2008] [Accepted: 04/02/2008] [Indexed: 01/16/2023] Open
Abstract
Glutaredoxins represent a ubiquitous family of proteins that catalyze the reduction of disulfide bonds in their substrate proteins by use of reduced glutathione. In an attempt to identify the full complement of glutaredoxins in baker's yeast, we found three so-far uncharacterized glutaredoxin-like proteins that we named Grx6, Grx7, and Grx8. Grx6 and Grx7 represent closely related monothiol glutaredoxins that are synthesized with N-terminal signal sequences. Both proteins are located in the cis-Golgi, thereby representing the first glutaredoxins found in a compartment of the secretory pathway. In contrast to formerly described monothiol glutaredoxins, Grx6 and Grx7, showed a high glutaredoxin activity in vitro. Grx6 and Grx7 overlap in their activity and deletion mutants lacking both proteins show growth defects and a strongly increased sensitivity toward oxidizing agents such as hydrogen peroxide or diamide. Our observations suggest that Grx6 and Grx7 do not play a general role in the oxidative folding of proteins in the early secretory pathway but rather counteract the oxidation of specific thiol groups in substrate proteins.
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Affiliation(s)
- Nikola Mesecke
- *Institute of Physiological Chemistry, University of Munich, 81377 Munich, Germany
- Cell Biology, University of Kaiserslautern, 67663 Kaiserslautern, Germany
| | - Anne Spang
- Biozentrum, University of Basel, CH-4056 Basel, Switzerland; and
| | - Marcel Deponte
- *Institute of Physiological Chemistry, University of Munich, 81377 Munich, Germany
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Mesecke N, Mittler S, Eckers E, Herrmann JM, Deponte M. Two Novel Monothiol Glutaredoxins from Saccharomyces cerevisiae Provide Further Insight into Iron-Sulfur Cluster Binding, Oligomerization, and Enzymatic Activity of Glutaredoxins. Biochemistry 2008; 47:1452-63. [DOI: 10.1021/bi7017865] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Nikola Mesecke
- Adolf-Butenandt-Institut für Physiologische Chemie, Ludwig-Maximilians Universität D-81377, München, and the Institut für Zellbiologie, Technische Universität Kaiserslautern D-67663, Kaiserslautern, Germany
| | - Sarah Mittler
- Adolf-Butenandt-Institut für Physiologische Chemie, Ludwig-Maximilians Universität D-81377, München, and the Institut für Zellbiologie, Technische Universität Kaiserslautern D-67663, Kaiserslautern, Germany
| | - Elisabeth Eckers
- Adolf-Butenandt-Institut für Physiologische Chemie, Ludwig-Maximilians Universität D-81377, München, and the Institut für Zellbiologie, Technische Universität Kaiserslautern D-67663, Kaiserslautern, Germany
| | - Johannes M. Herrmann
- Adolf-Butenandt-Institut für Physiologische Chemie, Ludwig-Maximilians Universität D-81377, München, and the Institut für Zellbiologie, Technische Universität Kaiserslautern D-67663, Kaiserslautern, Germany
| | - Marcel Deponte
- Adolf-Butenandt-Institut für Physiologische Chemie, Ludwig-Maximilians Universität D-81377, München, and the Institut für Zellbiologie, Technische Universität Kaiserslautern D-67663, Kaiserslautern, Germany
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24
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Sherman IW. References. ADVANCES IN PARASITOLOGY 2008. [DOI: 10.1016/s0065-308x(08)00430-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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25
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Kawazu SI, Komaki-Yasuda K, Oku H, Kano S. Peroxiredoxins in malaria parasites: parasitologic aspects. Parasitol Int 2007; 57:1-7. [PMID: 17890140 DOI: 10.1016/j.parint.2007.08.001] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2007] [Revised: 08/02/2007] [Accepted: 08/04/2007] [Indexed: 11/30/2022]
Abstract
Malaria is one of the most debilitating and life threatening diseases in tropical regions of the world. Over 500 million clinical cases occur, and 2-3 million people die of the disease each year. Because Plasmodium lacks genuine glutathione peroxidase and catalase, the two major antioxidant enzymes in the eukaryotic cell, malaria parasites are likely to utilize members of the peroxiredoxin (Prx) family as the principal enzymes to reduce peroxides, which increase in the parasite cell due to metabolism and parasitism during parasite development. In addition to its function of protecting macromolecules from H(2)O(2), Prx has also been reported to regulate H(2)O(2) as second messenger in transmission of redox signals, which mediate cell proliferation, differentiation, and apoptosis. In the malaria parasite, several lines of experimental data have suggested that the parasite uses Prxs as multifunctional molecules to adapt themselves to asexual and sexual development. In this review, we summarize the accumulated knowledge on the Prx family with respect to their functions in mammalian cells and their possible function(s) in malaria parasites.
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Affiliation(s)
- Shin-ichiro Kawazu
- National Research Center for Protozoan Diseases, Obihiro University of Agriculture and Veterinary Medicine, 2-13 Inada-cho, Obihiro, Hokkaido 080-8555, Japan.
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26
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Melchers J, Dirdjaja N, Ruppert T, Krauth-Siegel RL. Glutathionylation of Trypanosomal Thiol Redox Proteins. J Biol Chem 2007; 282:8678-94. [PMID: 17242409 DOI: 10.1074/jbc.m608140200] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Trypanosomatids, the causative agents of several tropical diseases, lack glutathione reductase and thioredoxin reductase but have a trypanothione reductase instead. The main low molecular weight thiols are trypanothione (N(1),N(8)-bis-(glutathionyl)spermidine) and glutathionyl-spermidine, but the parasites also contain free glutathione. To elucidate whether trypanosomes employ S-thiolation for regulatory or protection purposes, six recombinant parasite thiol redox proteins were studied by ESI-MS and MALDI-TOF-MS for their ability to form mixed disulfides with glutathione or glutathionylspermidine. Trypanosoma brucei mono-Cys-glutaredoxin 1 is specifically thiolated at Cys(181). Thiolation of this residue induced formation of an intramolecular disulfide bridge with the putative active site Cys(104). This contrasts with mono-Cys-glutaredoxins from other sources that have been reported to be glutathionylated at the active site cysteine. Both disulfide forms of the T. brucei protein were reduced by tryparedoxin and trypanothione, whereas glutathione cleaved only the protein disulfide. In the glutathione peroxidase-type tryparedoxin peroxidase III of T. brucei, either Cys(47) or Cys(95) became glutathionylated but not both residues in the same protein molecule. T. brucei thioredoxin contains a third cysteine (Cys(68)) in addition to the redox active dithiol/disulfide. Treatment of the reduced protein with GSSG caused glutathionylation of Cys(68), which did not affect its capacity to catalyze reduction of insulin disulfide. Reduced T. brucei tryparedoxin possesses only the redox active Cys(32)-Cys(35) couple, which upon reaction with GSSG formed a disulfide. Also glyoxalase II and Trypanosoma cruzi trypanothione reductase were not sensitive to thiolation at physiological GSSG concentrations.
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Abstract
Cellular redox metabolism is considered to be involved in the pathophysiology of diseases caused by protozoal parasites such as Toxoplasma, Trypanosoma, Leishmania, and Plasmodia. Redox reactions furthermore are thought to play a major role in the action of and the resistance to some clinically used antiparasitic drugs. Interestingly, in malarial parasites, the antioxidant enzymes catalase and glutathione peroxidase are absent which indicates a crucial role of the thioredoxin system in redox control. Besides a glutathione peroxidase-like thioredoxin peroxidase and a glutathione S-transferase with slight peroxidase activity, Plasmodium falciparum (the causative agent of tropical malaria) possesses four classical peroxiredoxins: Two peroxiredoxins of the typical 2-Cys Prx class, one 1-Cys peroxiredoxin with homology to the atypical 2-Cys Prx class, and a peroxiredoxin of the 1-Cys Prx class have been identified and partially characterized In our article we give an introduction to redox-based drug development strategies against protozoal parasites and summarize the present knowledge on peroxiredoxin systems in Plasmodium.
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Affiliation(s)
- Marcel Deponte
- Interdisciplinary Research Center, Justus Liebig University, D-35392 Giessen, Germany
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28
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Herrero E, Ros J, Tamarit J, Bellí G. Glutaredoxins in fungi. PHOTOSYNTHESIS RESEARCH 2006; 89:127-40. [PMID: 16915356 DOI: 10.1007/s11120-006-9079-3] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/30/2006] [Accepted: 06/09/2006] [Indexed: 05/11/2023]
Abstract
Glutaredoxins (GRXs) can be subdivided into two subfamilies: dithiol GRXs with the CPY/FC active site motif, and monothiol GRXs with the CGFS motif. Both subfamilies share a thioredoxin-fold structure. Some monothiol GRXs exist with a single-Grx domain while others have a thioredoxin-like domain (Trx) and one or more Grx domains in tandem. Most fungi have both dithiol and monothiol GRXs with different subcellular locations. GRX-like molecules also exist in fungi that differ by one residue from one of the canonical active site motifs. Additionally, Omega-class glutathione transferases (GSTs) are active as GRXs. Among fungi, the GRXs more extensively studied are those from Saccharomyces cerevisiae. This organism contains two dithiol GRXs (ScGrx1 and ScGrx2) with partially overlapping functions in defence against oxidative stress. In this function, they cooperate with GSTs Gtt1 and Gtt2. While ScGrx1 is cytosolic, two pools exist for ScGrx2, a major one at the cytosol and a minor one at mitochondria. On the other hand, S. cerevisiae cells have two monothiol GRXs with the Trx-Grx structure (ScGrx3 and ScGrx4) that locate at the nucleus and probably regulate the activity of transcription factors such as Aft1, and one monothiol GRX with the Grx structure (ScGrx5) that localizes at the mitochondrial matrix, where it participates in the synthesis of iron-sulphur clusters. The function of yeast Grx5 seems to be conserved along the evolutionary scale.
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Affiliation(s)
- Enrique Herrero
- Departament de Ciències Mèdiques Bàsiques, Facultat de Medicina, Universitat de Lleida, Montserrat Roig 2, 25008, Lleida, Spain.
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Molina-Navarro MM, Casas C, Piedrafita L, Bellí G, Herrero E. Prokaryotic and eukaryotic monothiol glutaredoxins are able to perform the functions of Grx5 in the biogenesis of Fe/S clusters in yeast mitochondria. FEBS Lett 2006; 580:2273-80. [PMID: 16566929 DOI: 10.1016/j.febslet.2006.03.037] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2006] [Revised: 03/08/2006] [Accepted: 03/09/2006] [Indexed: 12/19/2022]
Abstract
The Saccharomyces cerevisiae monothiol glutaredoxin Grx5 participates in the mitochondrial biogenesis of iron-sulfur clusters. Grx5 homologues exist in organisms from bacteria to humans. Chicken (cGRX5) and human (hGRX5) homologues contain a mitochondrial targeting sequence, suggesting a mitochondrial localization for these two proteins. We have compartmentalized the Escherichia coli and Synechocystis sp. homologues, and also cGRX5 and hGRX5, in the mitochondrial matrix of a yeast grx5 mutant. All four heterologous proteins rescue the defects of the mutant. The chicken cGRX5 gene was significantly expressed throughout the embryo stages in different tissues. These results underline the functional conservation of Grx5 homologues throughout evolution.
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Affiliation(s)
- Maria Micaela Molina-Navarro
- Departament de Ciències Mèdiques Bàsiques, Facultat de Medicina, Universitat de Lleida, Montserrat Roig 2, 25008-Lleida, Spain
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Nickel C, Trujillo M, Rahlfs S, Deponte M, Radi R, Becker K. Plasmodium falciparum 2-Cys peroxiredoxin reacts with plasmoredoxin and peroxynitrite. Biol Chem 2006; 386:1129-36. [PMID: 16307478 DOI: 10.1515/bc.2005.129] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Thioredoxin peroxidase 1 (TPx1) of the malarial parasite Plasmodium falciparum is a 2-Cys peroxiredoxin involved in the detoxification of reactive oxygen species and - as shown here - of reactive nitrogen species. As novel electron acceptor of reduced TPx1, we characterised peroxynitrite; the rate constant for ONOO- reduction by the enzyme (1 x 10(6) M(-1) s(-1) at pH 7.4 and 37 degrees C) was determined by stopped-flow measurements. As reducing substrate of TPx1, we identified - aside from thioredoxin - plasmoredoxin; this 22-kDa protein occurs only in malarial parasites. When studying the potential roles of Cys74 and Cys170 of Tpx1 in catalysis, as well as in oligomerisation behaviour, we found that replacement of Cys74 by Ala influenced neither the dimerisation nor enzymatic activity of TPx1. In the C170A mutant, however, the kcat/Km for reduced Trx as a substrate was shown to be approximately 50-fold lower and, in contrast to the wild-type enzyme, covalently linked dimers were not formed. For the catalytic cycle of TPx1, we conclude that oxidation of the peroxidatic Cys50 by the oxidising substrate is followed by the formation of an intermolecular disulfide bond between Cys50 and Cys170' of the second subunit, which is then attacked by an external electron donor such as thioredoxin or plasmoredoxin.
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Affiliation(s)
- Christine Nickel
- Interdisciplinary Research Centre, Justus-Liebig-University, D-35392 Giessen, Germany
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Abstract
Hydroperoxide metabolism in diverse pathogens is reviewed under consideration of involved enzymes as potential drug targets. The common denominator of the peroxidase systems of Trypanosoma, Leishmania, Plasmodium, and Mycobacterium species is the use of NAD(P)H to reduce hydroperoxides including peroxynitrite via a flavin-containing disulfide reductase, a thioredoxin (Trx)-related protein and a peroxidase that operates with thiol catalysis. In Plasmodium falciparum, thioredoxin- and glutathione dependent systems appear to be linked via glutaredoxin and plasmoredoxin to terminal thioredoxin peroxidases belonging to both, the peroxiredoxin (Prx) and glutathione peroxidase (GPx) family. In Mycobacterium tuberculosis, a catalase-type peroxidase is complemented by the typical 2-C-Prx AhpC that, in contrast to most bacteria, is reduced by TrxC, and an atypical 2-C-Prx reduced by TrxB or C. A most complex variation of the scheme is found in trypanosomatids, where the unique redox metabolite trypanothione reduces the thioredoxin-related tryparedoxin, which fuels Prx- and GPx-type peroxidases as well as ribonucleotide reductase. In Trypanosoma brucei and Leishmania donovani the system has been shown to be essential for viability and virulence by inversed genetics. It is concluded that optimum efficacy can be expected from inhibitors of the most upstream components of the redox cascades. For trypanosomatids attractive validated drug targets are trypanothione reductase and trypanothione synthetase; for mycobacteria thioredoxin reductase appears most appealing, while in Plasmodium simultaneous inhibition of both the thioredoxin and the glutathione pathway appears advisable to avoid mutual substitution in co-substrate supply to the peroxidases. Financial and organisational needs to translate the scientific progress into applicable drugs are discussed under consideration of the socio-economic impact of the addressed diseases.
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Affiliation(s)
- Timo Jaeger
- MOLISA GmbH, Molecular Links Sachsen-Anhalt, Universitätsplatz 2, D-39106 Magdeburg, Germany.
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