1
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Jia Q, Sieburth D. Mitochondrial hydrogen peroxide positively regulates neuropeptide secretion during diet-induced activation of the oxidative stress response. Nat Commun 2021; 12:2304. [PMID: 33863916 PMCID: PMC8052458 DOI: 10.1038/s41467-021-22561-x] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2020] [Accepted: 03/17/2021] [Indexed: 12/17/2022] Open
Abstract
Mitochondria play a pivotal role in the generation of signals coupling metabolism with neurotransmitter release, but a role for mitochondrial-produced ROS in regulating neurosecretion has not been described. Here we show that endogenously produced hydrogen peroxide originating from axonal mitochondria (mtH2O2) functions as a signaling cue to selectively regulate the secretion of a FMRFamide-related neuropeptide (FLP-1) from a pair of interneurons (AIY) in C. elegans. We show that pharmacological or genetic manipulations that increase mtH2O2 levels lead to increased FLP-1 secretion that is dependent upon ROS dismutation, mitochondrial calcium influx, and cysteine sulfenylation of the calcium-independent PKC family member PKC-1. mtH2O2-induced FLP-1 secretion activates the oxidative stress response transcription factor SKN-1/Nrf2 in distal tissues and protects animals from ROS-mediated toxicity. mtH2O2 levels in AIY neurons, FLP-1 secretion and SKN-1 activity are rapidly and reversibly regulated by exposing animals to different bacterial food sources. These results reveal a previously unreported role for mtH2O2 in linking diet-induced changes in mitochondrial homeostasis with neuropeptide secretion.
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Affiliation(s)
- Qi Jia
- PIBBS program, Keck School of Medicine, University of Southern California, Los Angeles, CA, USA
| | - Derek Sieburth
- Department of Physiology and Neuroscience, Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, CA, USA.
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2
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Joardar N, Guevara-Flores A, Martínez-González JDJ, Sinha Babu SP. Thiol antioxidant thioredoxin reductase: A prospective biochemical crossroads between anticancer and antiparasitic treatments of the modern era. Int J Biol Macromol 2020; 165:249-267. [DOI: 10.1016/j.ijbiomac.2020.09.096] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2020] [Revised: 09/10/2020] [Accepted: 09/14/2020] [Indexed: 02/08/2023]
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3
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Ferguson GD, Bridge WJ. The glutathione system and the related thiol network in Caenorhabditis elegans. Redox Biol 2019. [DOI: 10.1110.1016/j.redox.2019.101171] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
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4
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Badiea EA, Sayed AA, Maged M, Fouad WM, Said MM, Esmat AY. A novel thermostable and halophilic thioredoxin reductase from the Red Sea Atlantis II hot brine pool. PLoS One 2019; 14:e0217565. [PMID: 31150456 PMCID: PMC6544261 DOI: 10.1371/journal.pone.0217565] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2019] [Accepted: 05/14/2019] [Indexed: 11/19/2022] Open
Abstract
The highly extreme conditions of the lower convective layer in the Atlantis II (ATII) Deep brine pool of the Red Sea make it an ideal environment for the search for novel enzymes that can function under extreme conditions. In the current study, we isolated a novel sequence of a thioredoxin reductase (TrxR) enzyme from the metagenomic dataset established from the microbial community that resides in the lower convective layer of Atlantis II. The gene was cloned, expressed and characterized for redox activity, halophilicity, and thermal stability. The isolated thioredoxin reductase (ATII-TrxR) was found to belong to the high-molecular-weight class of thioredoxin reductases. A search for conserved domains revealed the presence of an extra domain (Crp) in the enzyme sequence. Characterization studies of ATII-TrxR revealed that the enzyme was halophilic (maintained activity at 4 M NaCl), thermophilic (optimum temperature was 65°C) and thermostable (60% of its activity was retained at 70°C). Additionally, the enzyme utilized NADH in addition to NADPH as an electron donor. In conclusion, a novel thermostable and halophilic thioredoxin reductase has been isolated with a unique sequence that adapts to the harsh conditions of the brine pools making this protein a good candidate for biological research and industrial applications.
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Affiliation(s)
- Elham A. Badiea
- Department of Biochemistry, Faculty of Science, Ain Shams University, Cairo, Egypt
- Department of Biology, School of Sciences and Engineering, American University in Cairo, New Cairo, Egypt
| | - Ahmed A. Sayed
- Department of Biochemistry, Faculty of Science, Ain Shams University, Cairo, Egypt
- Children Cancer Hospital, Cairo, Egypt
| | - Mohamad Maged
- Faculty of Biotechnology, October University for Modern Sciences and Arts, 6th October City, Cairo, Egypt
| | - Walid M. Fouad
- Department of Biology, School of Sciences and Engineering, American University in Cairo, New Cairo, Egypt
| | - Mahmoud M. Said
- Department of Biochemistry, Faculty of Science, Ain Shams University, Cairo, Egypt
| | - Amr Y. Esmat
- Department of Biochemistry, Faculty of Science, Ain Shams University, Cairo, Egypt
- * E-mail:
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5
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Ferguson GD, Bridge WJ. The glutathione system and the related thiol network in Caenorhabditis elegans. Redox Biol 2019; 24:101171. [PMID: 30901603 PMCID: PMC6429583 DOI: 10.1016/j.redox.2019.101171] [Citation(s) in RCA: 55] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2018] [Revised: 03/07/2019] [Accepted: 03/13/2019] [Indexed: 01/09/2023] Open
Abstract
Advances in the field of redox biology have contributed to the understanding of the complexity of the thiol-based system in mediating signal transduction. The redox environment is the overall spatiotemporal balance of oxidation-reduction systems within the integrated compartments of the cell, tissues and whole organisms. The ratio of the reduced to disulfide glutathione redox couple (GSH:GSSG) is a key indicator of the redox environment and its associated cellular health. The reaction mechanisms of glutathione-dependent and related thiol-based enzymes play a fundamental role in the function of GSH as a redox regulator. Glutathione homeostasis is maintained by the balance of GSH synthesis (de novo and salvage pathways) and its utilization through its detoxification, thiol signalling, and antioxidant defence functions via GSH-dependent enzymes and free radical scavenging. As such, GSH acts in concert with the entire redox network to maintain reducing conditions in the cell. Caenorhabditis elegans offers a simple model to facilitate further understanding at the multicellular level of the physiological functions of GSH and the GSH-dependent redox network. This review discusses the C. elegans studies that have investigated glutathione and related systems of the redox network including; orthologs to the protein-encoding genes of GSH synthesis; glutathione peroxidases; glutathione-S-transferases; and the glutaredoxin, thioredoxin and peroxiredoxin systems.
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Affiliation(s)
- Gavin Douglas Ferguson
- School of Biotechnology and Biomolecular Sciences, The University of New South Wales, Sydney, NSW, 2052, Australia
| | - Wallace John Bridge
- School of Biotechnology and Biomolecular Sciences, The University of New South Wales, Sydney, NSW, 2052, Australia.
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6
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Salgueiro WG, Goldani BS, Peres TV, Miranda-Vizuete A, Aschner M, da Rocha JBT, Alves D, Ávila DS. Insights into the differential toxicological and antioxidant effects of 4-phenylchalcogenil-7-chloroquinolines in Caenorhabditis elegans. Free Radic Biol Med 2017; 110:133-141. [PMID: 28571752 DOI: 10.1016/j.freeradbiomed.2017.05.020] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/18/2016] [Revised: 05/18/2017] [Accepted: 05/24/2017] [Indexed: 01/01/2023]
Abstract
Organic selenium and tellurium compounds are known for their broad-spectrum effects in a variety of experimental disease models. However, these compounds commonly display high toxicity and the molecular mechanisms underlying these deleterious effects have yet to be elucidated. Thus, the need for an animal model that is inexpensive, amenable to high-throughput analyses, and feasible for molecular studies is highly desirable to improve organochalcogen pharmacological and toxicological characterization. Herein, we use Caenorhabdtis elegans (C. elegans) as a model for the assessment of pharmacological and toxicological parameters following exposure to two 4-phenylchalcogenil-7-chloroquinolines derivatives (PSQ for selenium and PTQ for tellurium-containing compounds). While non-lethal concentrations (NLC) of PTQ and PSQ attenuated paraquat-induced effects on survival, lifespan and oxidative stress parameters, lethal concentrations (LC) of PTQ and PSQ alone are able to impair these parameters in C. elegans. We also demonstrate that DAF-16/FOXO and SKN-1/Nrf2 transcription factors underlie the mechanism of action of these compounds, as their targets sod-3, gst-4 and gcs-1 were modulated following exposures in a daf-16- and skn-1-dependent manner. Finally, in accordance with a disturbed thiol metabolism in both LC and NLC, we found higher sensitivity of trxr-1 worm mutants (lacking the selenoprotein thioredoxin reductase 1) when exposed to PSQ. Finally, our study suggests new targets for the investigation of organochalcogen pharmacological effects, reinforcing the use of C. elegans as a powerful platform for preclinical approaches.
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Affiliation(s)
- Willian G Salgueiro
- Grupo de Pesquisa em Bioquímica e Toxicologia em Caenorhabditis elegans (GBToxCE),Universidade Federal do Pampa - UNIPAMPA, CEP 97500-970 Uruguaiana, RS, Brazil
| | - Bruna S Goldani
- Laboratório de Síntese Orgânica Limpa - LASOL - CCQFA - Universidade Federal de Pelotas - UFPel, CEP 96010-900 Pelotas, RS, Brazil
| | - Tanara V Peres
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461, USA
| | - Antonio Miranda-Vizuete
- Instituto de Biomedicina de Sevilla, Hospital Universitario Virgen del Rocío/CSIC/Universidad de Sevilla, E-41013 Sevilla, Spain
| | - Michael Aschner
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461, USA
| | - João Batista Teixeira da Rocha
- Departamento de Bioquímica e Biologia Molecular, CCNE, Universidade Federal de Santa Maria, 97105-900 Santa Maria, RS, Brazil
| | - Diego Alves
- Laboratório de Síntese Orgânica Limpa - LASOL - CCQFA - Universidade Federal de Pelotas - UFPel, CEP 96010-900 Pelotas, RS, Brazil
| | - Daiana S Ávila
- Grupo de Pesquisa em Bioquímica e Toxicologia em Caenorhabditis elegans (GBToxCE),Universidade Federal do Pampa - UNIPAMPA, CEP 97500-970 Uruguaiana, RS, Brazil.
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7
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Elvitigala DAS, Whang I, Lee J. Molecular profiling and functional insights of rock bream (Oplegnathus fasciatus) thioredoxin reductase 3-like molecule: investigation of its transcriptional modulation in response to live pathogen stress. Gene 2015; 570:122-31. [PMID: 26055087 DOI: 10.1016/j.gene.2015.06.007] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2015] [Revised: 05/20/2015] [Accepted: 06/03/2015] [Indexed: 01/22/2023]
Abstract
The thioredoxin (Trx) system plays a significant role in cellular antioxidative defense by dismutating the surpluses of reactive oxygen species. Thus, the role of thioredoxin reductase (TrxR) cannot be ignored, owing to its participation in initiating the Trx enzyme cascade. Here, we report the identification and molecular characterization of a teleostean TrxR (RbTrxR-3) ortholog that showed high similarity with the TrxR-3 isoforms of other vertebrates. The complete RbTrxR-3 coding sequence comprised 1800 nucleotides, encoding a 600-amino acid protein with a predicted molecular mass of ~66 kDa. RbTrxR-3 consisted of 16 exons separated by 15 introns and had a total length of 12,658 bp. In silico analysis of the RbTrxR-3 protein sequence revealed that it possesses typical TrxR domain architecture. Moreover, using multiple sequence alignment and pairwise sequence alignment strategies, we showed that RbTrxR-3 has high overall sequence similarity to other teleostean TrxR-3 proteins, including highly conserved active site residues. Phylogenetic reconstruction of RbTrxR-3 affirmed its close evolutionary relationship with fish TrxR-3 orthologs, as indicated by its clustering pattern. RbTrxR-3 transcriptional analysis, performed using quantitative polymerase chain reaction (qPCR), showed that RbTrxR-3 was ubiquitously distributed, with the highest level of mRNA expression in the blood, followed by the gill, and liver. Live bacterial and viral stimuli triggered the modulation of RbTrxR-3 basal transcription in liver tissues that correlated temporally with that of its putative substrate, rock bream thioredoxin1 under the same conditions of pathogenic stress. Finally, resembling the typical function of TrxR protein, purified recombinant RbTrxR-3 showed detectable dose-dependent thiol reductase activity against 5,5'-dithiobis (2-nitrobenzoic) acid. Taken together, these results suggest that RbTrxR-3 plays a role in the host Trx system under conditions of oxidative and pathogenic stress.
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Affiliation(s)
- Don Anushka Sandaruwan Elvitigala
- Department of Marine Life Sciences, School of Marine Biomedical Sciences, Jeju National University, Jeju Self-Governing Province 690-756, Republic of Korea; Fish Vaccine Research Center, Jeju National University, Jeju Self-Governing Province 690-756, Republic of Korea
| | - Ilson Whang
- Fish Vaccine Research Center, Jeju National University, Jeju Self-Governing Province 690-756, Republic of Korea.
| | - Jehee Lee
- Department of Marine Life Sciences, School of Marine Biomedical Sciences, Jeju National University, Jeju Self-Governing Province 690-756, Republic of Korea; Fish Vaccine Research Center, Jeju National University, Jeju Self-Governing Province 690-756, Republic of Korea.
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8
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Effect of CDNB on filarial thioredoxin reductase : A proteomic and biochemical approach. J Proteomics 2015; 113:435-46. [DOI: 10.1016/j.jprot.2014.10.007] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2014] [Revised: 09/29/2014] [Accepted: 10/15/2014] [Indexed: 02/04/2023]
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9
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Shaykholeslam Esfahani E, Shahpiri A. Thioredoxin h isoforms from rice are differentially reduced by NADPH/thioredoxin or GSH/glutaredoxin systems. Int J Biol Macromol 2014; 74:243-8. [PMID: 25541357 DOI: 10.1016/j.ijbiomac.2014.12.033] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2014] [Revised: 12/02/2014] [Accepted: 12/03/2014] [Indexed: 01/01/2023]
Abstract
Rice (Oryza sativa L.) has multiple potential genes encoding thioredoxin (Trx) h and NADP-thioredoxin reductase (NTR). These NTR and Trx h isoforms, known as cytoplasmic NTR/Trx system along with multiple members of glutaredoxin (Grx) family constitute a complex redox control system in rice. In the present study, we investigated the kinetic parameters of two rice NTRs, OsNTRA and OsNTRB, toward three endogenous Trx h isoforms, OsTrx1, OsTrx20, and OsTrx23. The results showed that in contrast with OsTrx1 and OsTrx23, the isoform OsTrx20 was not reduced by OsNTR isoforms. The kcat/Km values of OsNTRB and OsNTRA toward OsTrx1 was six- and 13-fold higher than those values toward OsTrx23, respectively, suggesting that OsNTR isoforms do not reduce different OsTrx h isoforms, equivalently. Furthermore, the possible reduction of OsTrx isoforms by the glutathione (GSH)/Grx system was investigated through the heterologous expression of a gene encoding OsGrx9, a bicysteinic CPYC Grx found in rice. Whereas OsTrx23 was not reduced by GSH, OsTrx20 and with less efficiently OsTrx1 were reduced by GSH or GSH/Grx. Therefore, it seems that OsTrx1 can be reduced either by OsNTR or GSH/Grx. These data for the first time provides an evidence for cross-talking between NTR/Trx and GSH/Grx systems in rice.
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Affiliation(s)
- Ehsan Shaykholeslam Esfahani
- Department of Agricultural Biotechnology, College of Agriculture, Isfahan University of Technology, Isfahan 84156-83111, Iran
| | - Azar Shahpiri
- Department of Agricultural Biotechnology, College of Agriculture, Isfahan University of Technology, Isfahan 84156-83111, Iran.
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10
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Snider GW, Dustin CM, Ruggles EL, Hondal RJ. A mechanistic investigation of the C-terminal redox motif of thioredoxin reductase from Plasmodium falciparum. Biochemistry 2014; 53:601-9. [PMID: 24400600 PMCID: PMC3957191 DOI: 10.1021/bi400931k] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
![]()
High-molecular
mass thioredoxin reductases (TRs) are pyridine nucleotide
disulfide oxidoreductases that catalyze the reduction of the disulfide
bond of thioredoxin (Trx). Trx is responsible for reducing multiple
protein disulfide targets in the cell. TRs utilize reduced β-nicotinamide
adenine dinucleotide phosphate to reduce a bound flavin prosthetic
group, which in turn reduces an N-terminal redox center that has the
conserved sequence CICVNVGCCT, where CIC is denoted as the interchange thiol while the thiol involved in
charge-transfer complexation is denoted as CCT. The reduced
N-terminal redox center reduces a C-terminal redox center on the opposite
subunit of the head-to-tail homodimer, the C-terminal redox center
that catalyzes the reduction of the Trx-disulfide. Variations in the
amino acid sequence of the C-terminal redox center differentiate high-molecular
mass TRs into different types. Type Ia TRs have tetrapeptide C-terminal
redox centers of with a GCUG sequence, where U is the rare amino acid
selenocysteine (Sec), while the tetrapeptide sequence in type Ib TRs
has its Sec residue replaced with a conventional cysteine (Cys) residue
and can use small polar amino acids such as serine and threonine in
place of the flanking glycine residues. The TR from Plasmodium
falciparum (PfTR) is similar in structure and mechanism to
type Ia and type Ib TRs except that the C-terminal redox center is
different in its amino acid sequence. The C-terminal redox center
of PfTR has the sequence G534CGGGKCG541, and
we classify it as a type II high-molecular mass TR. The oxidized type
II redox motif will form a 20-membered disulfide ring, whereas the
absence of spacer amino acids in the type I motif results in the formation
of a rare eight-membered ring. We used site-directed mutagenesis and
protein semisynthesis to investigate features of the distinctive type
II C-terminal redox motif that help it perform catalysis. Deletion
of Gly541 reduces thioredoxin reductase activity by ∼50-fold,
most likely because of disruption of an important hydrogen bond between
the amide NH group of Gly541 and the carbonyl of Gly534 that helps
to stabilize
the β–turn−β motif. Alterations of the 20-membered
disulfide ring either by amino acid deletion or by substitution resulted
in impaired catalytic activity. Subtle changes in the ring structure
and size caused by using semisynthesis to substitute homocysteine
for cysteine also caused significant reductions in catalytic activity,
demonstrating the importance of the disulfide ring’s geometry
in making the C-terminal redox center reactive for thiol–disulfide
exchange. The data suggested to us that the transfer of electrons
from the N-terminal redox center to the C-terminal redox center may
be rate-limiting. We propose that the transfer of electrons from the
N-terminal redox center in PfTR to the type II C-terminal disulfide
is accelerated by the use of an “electrophilic activation”
mechanism. In this mechanism, the type II C-terminal disulfide is
polarized, making the sulfur atom of Cys540 electron deficient, highly
electrophilic, and activated for thiol–disulfide exchange with
the N-terminal redox center. This hypothesis was investigated by constructing
chimeric PfTR mutant enzymes containing C-terminal type I sequences
GCCG and GCUG, respectively. The PfTR-GCCG chimera had 500-fold less
thioredoxin reductase activity than the native enzyme but still reduced
selenocystine and lipoic acid efficiently. The PfTR-GCUG chimera had
higher catalytic activity than the native enzyme with Trx, selenocystine,
and lipoic acid as substrates. The results suggested to us that (i)
Sec in the mutant enzyme accelerated the rate of thiol–disulfide
exchange between the N- and C-terminal redox centers, (ii) the type
II redox center evolved for efficient catalysis utilizing Cys instead
of Sec, and (iii) the type II redox center of PfTR is partly responsible
for substrate recognition of the cognate PfTrx substrate relative
to noncognate thioredoxins.
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Affiliation(s)
- Gregg W Snider
- Department of Biochemistry, University of Vermont, College of Medicine , 89 Beaumont Avenue, Given Building Room B413, Burlington, Vermont 05405, United States
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11
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Lothrop AP, Snider GW, Ruggles EL, Hondal RJ. Why is mammalian thioredoxin reductase 1 so dependent upon the use of selenium? Biochemistry 2014; 53:554-65. [PMID: 24393022 PMCID: PMC3957196 DOI: 10.1021/bi400651x] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Cytosolic thioredoxin reductase 1 (TR1) is the best characterized of the class of high-molecular weight (Mr) thioredoxin reductases (TRs). TR1 is highly dependent upon the rare amino acid selenocysteine (Sec) for the reduction of thioredoxin (Trx) and a host of small molecule substrates, as mutation of Sec to cysteine (Cys) results in a large decrease in catalytic activity for all substrate types. Previous work in our lab and others has shown that the mitochondrial TR (TR3) is much less dependent upon the use of Sec for the reduction of small molecules. The Sec-dependent substrate utilization behavior of TR1 may be the exception and not the rule as we show that a variety of high-Mr TRs from other organisms, including Drosophila melanogaster, Caenorhabditis elegans, and Plasmodium falciparum, do not require Sec to reduce small molecule substrates, including 5,5'-dithiobis(2-nitrobenzoic acid), lipoic acid, selenite, and selenocystine. The data show that high-Mr TRs can be divided into two groups based upon substrate utilization patterns: a TR1 group and a TR3-like group. We have constructed mutants of TR3-like enzymes from mouse, D. melanogaster, C. elegans, and P. falciparum, and the kinetic data from these mutants show that these enzymes are less dependent upon the use of Sec for the reduction of substrates. We posit that the mechanistic differences between TR1 and the TR3-like enzymes in this study are due to the presence of a "guiding bar", amino acids 407-422, found in TR1, but not TR3-like enzymes. The guiding bar, proposed by Becker and co-workers [Fritz-Wolf, K., Urig, S., and Becker, K. (2007) The structure of human thioredoxin reductase 1 provides insights into C-terminal rearrangements during catalysis. J. Mol. Biol. 370, 116-127], restricts the motion of the C-terminal tail containing the C-terminal Gly-Cys-Sec-Gly, redox active tetrapeptide so that only this C-terminal redox center can be reduced by the N-terminal redox center, with the exclusion of most other substrates. This makes TR1 highly dependent upon the use of Sec because the selenium atom is responsible for both accepting electrons from the N-terminal redox center and donating them to the substrate in this model. Loss of both Se-electrophilicity and Se-nucleophilicity in the Sec → Cys mutant of TR1 greatly reduces catalytic activity. TR3-like enzymes, in contrast, are less dependent upon the use of Sec because the absence of the guiding bar in these enzymes allows for greater access of the substrate to the N-terminal redox center and because they can make use of alternative mechanistic pathways that are not available to TR1.
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Affiliation(s)
- Adam P Lothrop
- Department of Biochemistry, University of Vermont , 89 Beaumont Avenue, Given Building Room B413, Burlington, Vermont 05405, United States
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12
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Li W, Bandyopadhyay J, Hwaang HS, Park BJ, Cho JH, Lee JI, Ahnn J, Lee SK. Two thioredoxin reductases, trxr-1 and trxr-2, have differential physiological roles in Caenorhabditis elegans. Mol Cells 2012; 34:209-18. [PMID: 22836943 PMCID: PMC3887811 DOI: 10.1007/s10059-012-0155-6] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2012] [Revised: 07/03/2012] [Accepted: 07/04/2012] [Indexed: 10/28/2022] Open
Abstract
Thioredoxin reductase (TrxR) is a member of the pyridine nucleotide-disulfide reductase family, which mainly functions in the thioredoxin system. TrxR is found in all living organisms and exists in two major ubiquitous isoenzymes in higher eukaryotic cells; One is cytosolic and the other mitochondrial. Mitochondrial TrxR functions to protect mitochondria from oxidative stress, where reactive oxidative species are mainly generated, while cytosolic TrxR plays a role to maintain optimal oxido-reductive status in cytosol. In this study, we report differential physiological functions of these two TrxRs in C. elegans. trxr-1, the cytosolic TrxR, is highly expressed in pharynx, vulva and intestine, whereas trxr-2, the mitochondrial TrxR, is mainly expressed in pharyngeal and body wall muscles. Deficiency of the non-selenoprotein trxr-2 caused defects in longevity and delayed development under stress conditions, while deletion mutation of the selenoprotein trxr-1 resulted in interference in acidification of lysosomal compartment in intestine. Interestingly, the acidification defect of trxr-1(jh143) deletion mutant was rescued, not only by selenocystein-containing wild type TRXR-1, but also cysteine-substituted mutant TRXR-1. Both trxr-1 and trxr-2 were up-regulated when worms were challenged by environmental stress such as heat shock. These results suggest that trxr-1 and trxr-2 function differently at organismal level presumably by their differential sub-cellular localization in C. elegans.
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Affiliation(s)
- Weixun Li
- Department of Life Science, Hanyang University, Seoul 133-791,
Korea
- Brain Korea 21 Life Science for Global Warming Team, Hanyang University, Seoul 133-791,
Korea
| | - Jaya Bandyopadhyay
- Department of Biotechnology, West Bengal University of Technology, Kolkata 700-064,
India
| | - Hyun Sook Hwaang
- Department of Bioengineering, Hanyang University, Seoul 133-791,
Korea
- Department of Chemistry, Hanyang University, Seoul 133-791,
Korea
| | - Byung-Jae Park
- Department of Life Science, Hallym University, Chunchon 200-702,
Korea
| | - Jeong Hoon Cho
- Division of Biology Education, College of Education, Chosun University, Gwangju 501-759,
Korea
| | - Jin Il Lee
- Fred Hutchinson Cancer Research Center, Basic Sciences Division, 1100 Fairview Ave. N. Seattle, WA 98109,
USA
| | - Joohong Ahnn
- Department of Life Science, Hanyang University, Seoul 133-791,
Korea
- Brain Korea 21 Life Science for Global Warming Team, Hanyang University, Seoul 133-791,
Korea
- The Research Institute for Natural Sciences, Hanyang University, Seoul 133-791,
Korea
| | - Sun-Kyung Lee
- Department of Life Science, Hanyang University, Seoul 133-791,
Korea
- The Research Institute for Natural Sciences, Hanyang University, Seoul 133-791,
Korea
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13
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Cacho-Valadez B, Muñoz-Lobato F, Pedrajas JR, Cabello J, Fierro-González JC, Navas P, Swoboda P, Link CD, Miranda-Vizuete A. The characterization of the Caenorhabditis elegans mitochondrial thioredoxin system uncovers an unexpected protective role of thioredoxin reductase 2 in β-amyloid peptide toxicity. Antioxid Redox Signal 2012; 16:1384-400. [PMID: 22220943 PMCID: PMC3329951 DOI: 10.1089/ars.2011.4265] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
AIM Functional in vivo studies on the mitochondrial thioredoxin system are hampered by the embryonic or larval lethal phenotypes displayed by murine or Drosophila knock-out models. Thus, the access to alternative metazoan knock-out models for the mitochondrial thioredoxin system is of critical importance. RESULTS We report here the characterization of the mitochondrial thioredoxin system of Caenorhabditis elegans that is composed of the genes trx-2 and trxr-2. We demonstrate that the proteins thioredoxin 2 (TRX-2) and thioredoxin reductase 2 (TRXR-2) localize to the mitochondria of several cells and tissues of the nematode and that trx-2 and trxr-2 are upregulated upon induction of the mitochondrial unfolded protein response. Surprisingly, C. elegans trx-2 (lof ) and trxr-2 (null) single and double mutants are viable and display similar growth rates as wild-type controls. Moreover, the lack of the mitochondrial thioredoxin system does not affect longevity, reactive oxygen species production or the apoptotic program. Interestingly, we found a protective role of TRXR-2 in a transgenic nematode model of Alzheimer's disease (AD) that expresses human β-amyloid peptide and causes an age-dependent progressive paralysis. Hence, trxr-2 downregulation enhanced the paralysis phenotype, while a strong decrease of β-amyloid peptide and amyloid deposits occurred when TRXR-2 was overexpressed. INNOVATION C. elegans provides the first viable metazoan knock-out model for the mitochondrial thioredoxin system and identifies a novel role of this system in β-amyloid peptide toxicity and AD. CONCLUSION The nematode strains characterized in this work make C. elegans an ideal model organism to study the pathophysiology of the mitochondrial thioredoxin system at the level of a complete organism.
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Affiliation(s)
- Briseida Cacho-Valadez
- Centro Andaluz de Biología del Desarrollo (CABD-CSIC), Depto. de Fisiología, Anatomía y Biología Celular, Universidad Pablo de Olavide, Sevilla, Spain
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14
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Van Raamsdonk JM, Hekimi S. Reactive Oxygen Species and Aging in Caenorhabditis elegans: Causal or Casual Relationship? Antioxid Redox Signal 2010; 13:1911-53. [PMID: 20568954 DOI: 10.1089/ars.2010.3215] [Citation(s) in RCA: 138] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The free radical theory of aging proposes a causal relationship between reactive oxygen species (ROS) and aging. While it is clear that oxidative damage increases with age, its role in the aging process is uncertain. Testing the free radical theory of aging requires experimentally manipulating ROS production or detoxification and examining the resulting effects on lifespan. In this review, we examine the relationship between ROS and aging in the genetic model organism Caenorhabditis elegans, summarizing experiments using long-lived mutants, mutants with altered mitochondrial function, mutants with decreased antioxidant defenses, worms treated with antioxidant compounds, and worms exposed to different environmental conditions. While there is frequently a negative correlation between oxidative damage and lifespan, there are many examples in which they are uncoupled. Neither is resistance to oxidative stress sufficient for a long life nor are all long-lived mutants more resistant to oxidative stress. Similarly, sensitivity to oxidative stress does not necessarily shorten lifespan and is in fact compatible with long life. Overall, the data in C. elegans indicate that oxidative damage can be dissociated from aging in experimental situations.
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15
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Mitochondrial Thioredoxin-Glutathione Reductase from Larval Taenia crassiceps (Cysticerci). J Parasitol Res 2010; 2010. [PMID: 20798751 PMCID: PMC2925084 DOI: 10.1155/2010/719856] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2009] [Revised: 02/27/2010] [Accepted: 04/22/2010] [Indexed: 11/17/2022] Open
Abstract
Mitochondrial thioredoxin-glutathione reductase was purified from larval Taenia crassiceps (cysticerci). The preparation showed NADPH-dependent reductase activity with either thioredoxin or GSSG, and was able to perform thiol/disulfide exchange reactions. At 25°C specific activities were 437 ± 27 mU mg−1 and 840 ± 49 mU mg−1 with thioredoxin and GSSG, respectively. Apparent Km values were 0.87 ± 0.04 μM, 41 ± 6 μM and 19 ± 10 μM for thioredoxin, GSSG and NADPH, respectively. Thioredoxin from eukaryotic sources was accepted as substrate. The enzyme reduced H2O2 in a NADPH-dependent manner, although with low catalytic efficiency. In the presence of thioredoxin, mitochondrial TGR showed a thioredoxin peroxidase-like activity. All disulfide reductase activities were inhibited by auranofin, suggesting mTGR is dependent on selenocysteine. The reductase activity with GSSG showed a higher dependence on temperature as compared with the DTNB reductase activity. The variation of the GSSG- and DTNB reductase activities on pH was dependent on the disulfide substrate. Like the cytosolic isoform, mTGR showed a hysteretic kinetic behavior at moderate or high GSSG concentrations, but it was less sensitive to calcium. The enzyme was able to protect glutamine synthetase from oxidative inactivation, suggesting that mTGR is competent to contend with oxidative stress.
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16
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Substrate specificity of the mitochondrial thioredoxin reductase of the parasitic nematode Haemonchus contortus. Parasitol Res 2010; 107:487-93. [DOI: 10.1007/s00436-010-1916-9] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2010] [Accepted: 05/05/2010] [Indexed: 01/23/2023]
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17
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Nauser T, Steinmann D, Koppenol WH. Why do proteins use selenocysteine instead of cysteine? Amino Acids 2010; 42:39-44. [DOI: 10.1007/s00726-010-0602-7] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2009] [Accepted: 04/16/2010] [Indexed: 11/24/2022]
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18
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Hondal RJ, Ruggles EL. Differing views of the role of selenium in thioredoxin reductase. Amino Acids 2010; 41:73-89. [PMID: 20397034 DOI: 10.1007/s00726-010-0494-6] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2009] [Accepted: 01/21/2010] [Indexed: 12/01/2022]
Abstract
This review covers three different chemical explanations that could account for the requirement of selenium in the form of selenocysteine in the active site of mammalian thioredoxin reductase. These views are the following: (1) the traditional view of selenocysteine as a superior nucleophile relative to cysteine, (2) the superior leaving group ability of a selenol relative to a thiol due to its significantly lower pK (a) and, (3) the superior ability of selenium to accept electrons (electrophilicity) relative to sulfur. We term these chemical explanations as the "chemico-enzymatic" function of selenium in an enzyme. We formally define the chemico-enzymatic function of selenium as its specific chemical property that allows a selenoenzyme to catalyze its individual reaction. However we, and others, question whether selenocysteine is chemically necessary to catalyze an enzymatic reaction since cysteine-homologs of selenocysteine-containing enzymes catalyze their specific enzymatic reactions with high catalytic efficiency. There must be a unique chemical reason for the presence of selenocysteine in enzymes that explains the biological pressure on the genome to maintain the complex selenocysteine-insertion machinery. We term this biological pressure the "chemico-biological" function of selenocysteine. We discuss evidence that this chemico-biological function is the ability of selenoenzymes to resist inactivation by irreversible oxidation. The way in which selenocysteine confers resistance to oxidation could be due to the superior ability of the oxidized form of selenocysteine (Sec-SeO(2)(-), seleninic acid) to be recycled back to its parent form (Sec-SeH, selenocysteine) in comparison to the same cycling of cysteine-sulfinic acid to cysteine (Cys-SO(2)(-) to Cys-SH).
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Affiliation(s)
- Robert J Hondal
- Department of Biochemistry, College of Medicine, University of Vermont, Burlington, 05405, USA.
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19
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Hondal RJ. Using chemical approaches to study selenoproteins-focus on thioredoxin reductases. Biochim Biophys Acta Gen Subj 2009; 1790:1501-12. [PMID: 19406205 DOI: 10.1016/j.bbagen.2009.04.015] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2009] [Revised: 04/15/2009] [Accepted: 04/22/2009] [Indexed: 11/29/2022]
Abstract
The study of selenocysteine-containing proteins is difficult due to the problems associated with the heterologous production of these proteins. These problems are due to the intricate recoding mechanism used by cells to translate the UGA codon as a sense codon for selenocysteine. The process is further complicated by the fact that eukaryotes and prokaryotes have different UGA recoding machineries. This review focuses on chemical approaches to produce selenoproteins and study the mechanism of selenoenzymes. The use of intein-mediated peptide ligation is discussed with respect to the production of the mammalian selenoenzymes thioredoxin reductase and selenoprotein R, also known as methionine sulfoxide reductase B1. New methods for removing protecting groups from selenocysteine post-synthesis and methods for selenosulfide/diselenide formation are also reviewed. Chemical approaches have also been used to study the enzymatic mechanism of thioredoxin reductase. The approach divides the enzyme into two modules, a large protein module lacking selenocysteine and a small, synthetic selenocysteine-containing peptide. Study of this semisynthetic enzyme has revealed three distinct enzymatic pathways that depend on the properties of the substrate. The enzyme utilizes a macromolecular mechanism for protein substrates, a second mechanism for small molecule substrates and a third pathway for selenium-containing substrates such as selenocystine.
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Affiliation(s)
- Robert J Hondal
- Department of Biochemistry, University of Vermont, College of Medicine, 89 Beaumont Ave, Given Building Room B413, Burlington, VT 05405, USA.
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20
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Lu J, Zhong L, Lönn ME, Burk RF, Hill KE, Holmgren A. Penultimate selenocysteine residue replaced by cysteine in thioredoxin reductase from selenium-deficient rat liver. FASEB J 2009; 23:2394-402. [PMID: 19351701 DOI: 10.1096/fj.08-127662] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Selenium is an essential micronutrient for humans and animals, and its deficiency can predispose to the development of pathological conditions. This study evaluates the effect of selenium deficiency on the thioredoxin system, consisting of NADPH, selenoprotein thioredoxin reductase (TrxR), and thioredoxin (Trx); and the glutathione system, including NADPH, glutathione reductase, glutathione, and glutaredoxin coupled with selenoprotein glutathione peroxidase (GPx). We particularly investigate whether inactive truncated TrxR is present under selenium-starvation conditions due to reading of the UGA codon as stop. Feeding rats a selenium-deficient diet resulted in a large decrease in activity of TrxR and GPx in rat liver but not in the levels of Trx1 and Grx1. However, selenium deficiency induced mitochondrial Grx2 10-fold and markedly changed the expression of some flavoproteins that are involved in the cellular folate, glucose, and lipid metabolism. Liver TrxR mRNA was nearly unchanged, but no truncated enzyme was found. Instead, a low-activity form of TrxR with a cysteine substituted for the penultimate selenocysteine in the C-terminal active site was identified in selenium-deficient rat liver. These results show a novel mechanism for decoding the UGA stop codon, inserting cysteine to make a full-length enzyme that may be required for selenium assimilation.
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Affiliation(s)
- Jun Lu
- Department of Medical Biochemistry and Biophysics, Karolinska Institute, SE-171 77 Stockholm, Sweden
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21
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Lacey BM, Eckenroth BE, Flemer S, Hondal RJ. Selenium in thioredoxin reductase: a mechanistic perspective. Biochemistry 2009; 47:12810-21. [PMID: 18986163 DOI: 10.1021/bi800951f] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Most high M(r) thioredoxin reductases (TRs) have the unusual feature of utilizing a vicinal disulfide bond (Cys(1)-Cys(2)) which forms an eight-membered ring during the catalytic cycle. Many eukaryotic TRs have replaced the Cys(2) position of the dyad with the rare amino acid selenocysteine (Sec). Here we demonstrate that Cys- and Sec-containing TRs are distinguished by the importance each class of enzymes places on the eight-membered ring structure in the catalytic cycle. This hypothesis was explored by studying the truncated enzyme missing the C-terminal ring structure in conjunction with oxidized peptide substrates to investigate the reduction and opening of this dyad. The peptide substrates were identical in sequence to the missing part of the enzyme, containing either a disulfide or selenylsulfide linkage, but were differentiated by the presence (cyclic) and absence (acyclic) of the ring structure. The ratio of these turnover rates informs that the ring is only of modest importance for the truncated mouse mitochondrial Sec-TR (ring/no ring = 32), while the ring structure is highly important for the truncated Cys-TRs from Drosophila melanogaster and Caenorhabditis elegans (ring/no ring > 1000). All three enzymes exhibit a similar dependence upon leaving group pK(a) as shown by the use of the acyclic peptides as substrates. These two factors can be reconciled for Cys-TRs if the ring functions to simultaneously allow for attack by a nearby thiolate while correctly positioning the leaving group sulfur atom to accept a proton from the enzymic general acid. For Sec-TRs the ring is unimportant because the lower pK(a) of the selenol relative to a thiol obviates its need to be protonated upon S-Se bond scission and permits physical separation of the selenol and the general acid. Further study of the biochemical properties of the truncated Cys and Sec TR enzymes demonstrates that the chemical advantage conferred on the eukaryotic enzyme by a selenol is the ability to function at acidic pH.
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Affiliation(s)
- Brian M Lacey
- Department of Biochemistry, College of Medicine, University of Vermont, 89 Beaumont Avenue, Given Building Room B413, Burlington, Vermont 05405, USA
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22
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Flemer S, Lacey BM, Hondal RJ. Synthesis of peptide substrates for mammalian thioredoxin reductase. J Pept Sci 2008; 14:637-47. [PMID: 18035847 DOI: 10.1002/psc.961] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Mammalian thioredoxin reductase (TR) catalyzes the reduction of the redox-active disulfide bond of thioredoxin (Trx) and is similar in structure and mechanism to glutathione reductase except for a C-terminal 16-amino acid extension containing a rare vicinal selenylsulfide bond. This vicinal selenylsulfide bond is essentially a substrate for the enzyme's N-terminal redox center. Here we report the synthesis of peptide substrates for the truncated enzyme missing the C-terminal redox center. We developed a procedure for the synthesis of peptides containing cyclic vicinal disulfide/selenylsulfide bonds as well as their corresponding acyclic heterodimers. Vicinal disulfide bonds form eight-membered ring structures and are difficult to synthesize owing to their propensity to dimerize during oxidation. Our procedure makes use of two key improvements for on-resin disulfide bond formation presented previously by Galande and coworkers (Galande AK, Weissleder R, Tung C-H. An effective method of on-resin disulfide bond formation in peptides. J. Comb. Chem. 2005; 7: 174-177). First, the addition of an amine base to the deprotection solution allows the complete removal of the StBu group, allowing it to be replaced with a 5-Npys group. The second enhancement is the direct use of a Cys(Mob) or Sec(Mob) derivative as the nucleophilic partner instead of utilizing a naked sulfhydryl or selenol. These improvements result in the formation of a vicinal disulfide (or selenylsulfide) bond in high purity and yield. A direct comparison with the Galande procedure is presented. We also present a novel strategy for the formation of an acyclic, interchain selenylsulfide-linked peptide (linking H-PTVTGC-OH and H-UG-OH). Cysteine analogs of the cyclic and acyclic peptides were also synthesized. The results show that the ring structure contributes a factor of 52 to the rate, but the presence of selenium in the peptide is more important to catalysis than the presence of the ring.
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Affiliation(s)
- Stevenson Flemer
- Department of Biochemistry, Given Laboratory, Burlington, VT 05405, USA
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23
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Shahpiri A, Svensson B, Finnie C. The NADPH-dependent thioredoxin reductase/thioredoxin system in germinating barley seeds: gene expression, protein profiles, and interactions between isoforms of thioredoxin h and thioredoxin reductase. PLANT PHYSIOLOGY 2008; 146:789-99. [PMID: 18162587 PMCID: PMC2245843 DOI: 10.1104/pp.107.113639] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/21/2007] [Accepted: 12/12/2007] [Indexed: 05/25/2023]
Abstract
The NADPH-dependent thioredoxin reductase (NTR)/thioredoxin (Trx) system catalyzes disulfide bond reduction in the cytoplasm and mitochondrion. Trx h is suggested to play an important role in seed development, germination, and seedling growth. Plants have multiple isoforms of Trx h and NTR; however, little is known about the roles of the individual isoforms. Trx h isoforms from barley (Hordeum vulgare) seeds (HvTrxh1 and HvTrxh2) were characterized previously. In this study, two NTR isoforms (HvNTR1 and HvNTR2) were identified, enabling comparison of gene expression, protein appearance, and interaction between individual NTR and Trx h isoforms in barley embryo and aleurone layers. Although mRNA encoding both Trx h isoforms is present in embryo and aleurone layers, the corresponding proteins differed in spatiotemporal appearance. HvNTR2, but not HvNTR1, gene expression seems to be regulated by gibberellic acid. Recombinant HvNTR1 and HvNTR2 exhibited virtually the same affinity toward HvTrxh1 and HvTrxh2, whereas HvNTR2 has slightly higher catalytic activity than HvNTR1 with both Trx h isoforms, and HvNTR1 has slightly higher catalytic activity toward HvTrxh1 than HvTrxh2. Notably, both NTRs reduced Trx h at the acidic conditions residing in the starchy endosperm during germination. Interspecies reactions between the barley proteins and Escherichia coli Trx or Arabidopsis thaliana NTR, respectively, occurred with 20- to 90-fold weaker affinity. This first investigation of regulation and interactions between members of the NTR/Trx system in barley seed tissues suggests that different isoforms are differentially regulated but may have overlapping roles, with HvNTR2 and HvTrxh1 being the predominant isoforms in the aleurone layer.
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Affiliation(s)
- Azar Shahpiri
- Enzyme and Protein Chemistry, BioCentrum-DTU, Technical University of Denmark, DK-2800 Kgs. Lyngby, Denmark
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24
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Eckenroth BE, Lacey BM, Lothrop AP, Harris KM, Hondal RJ. Investigation of the C-terminal redox center of high-Mr thioredoxin reductase by protein engineering and semisynthesis. Biochemistry 2007; 46:9472-83. [PMID: 17661444 PMCID: PMC3682222 DOI: 10.1021/bi7004812] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
High-molecular weight thioredoxin reductases (TRs) catalyze the reduction of the redox-active disulfide bond of thioredoxin, but an important difference in the TR family is the sequence of the C-terminal redox-active tetrapeptide that interacts directly with thioredoxin, especially the presence or absence of a selenocysteine (Sec) residue in this tetrapeptide. In this study, we have employed protein engineering techniques to investigate the C-terminal redox-active tetrapeptides of three different TRs: mouse mitochondrial TR (mTR3), Drosophila melanogaster TR (DmTR), and the mitochondrial TR from Caenorhabditis elegans (CeTR2), which have C-terminal tetrapeptide sequences of Gly-Cys-Sec-Gly, Ser-Cys-Cys-Ser, and Gly-Cys-Cys-Gly, respectively. Three different types of mutations and chemical modifications were performed in this study: insertion of alanine residues between the cysteine residues of the Cys-Cys or Cys-Sec dyads, modification of the charge at the C-terminus, and altering the position of the Sec residue in the mammalian enzyme. The results show that mTR3 is quite accommodating to insertion of alanine residues into the Cys-Sec dyad, with only a 4-6-fold drop in catalytic activity. In contrast, the activity of both DmTR and CeTR2 was reduced 100-300-fold when alanine residues were inserted into the Cys-Cys dyad. We have tested the importance of a salt bridge between the C-terminus and a basic residue that was proposed for orienting the Cys-Sec dyad of mTR3 for proper catalytic position by changing the C-terminal carboxylate to a carboxamide. The result is an enzyme with twice the activity as the wild-type mammalian enzyme. A similar result was achieved when the C-terminal carboxylate of DmTR was converted to a hydroxamic acid or a thiocarboxylate. Last, reversing the positions of the Cys and Sec residues in the catalytic dyad resulted in a 100-fold loss of catalytic activity. Taken together, the results support our previous model of Sec as the leaving group during reduction of the C-terminus during the catalytic cycle.
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Affiliation(s)
- Brian E. Eckenroth
- Department of Biochemistry, 89 Beaumont Ave, Given Laboratory, Room B413, Burlington, VT 05405
| | - Brian M. Lacey
- Department of Biochemistry, 89 Beaumont Ave, Given Laboratory, Room B413, Burlington, VT 05405
| | - Adam P. Lothrop
- Department of Biochemistry, 89 Beaumont Ave, Given Laboratory, Room B413, Burlington, VT 05405
| | - Katharine M. Harris
- Department of Biochemistry, 89 Beaumont Ave, Given Laboratory, Room B413, Burlington, VT 05405
| | - Robert J. Hondal
- Department of Biochemistry, 89 Beaumont Ave, Given Laboratory, Room B413, Burlington, VT 05405
- To whom correspondence should be addressed. Department of Biochemistry, University of Vermont, College of Medicine. 89 Beaumont Ave, Given Laboratory, Room B413, Burlington, VT 05405. Tel: 802-656-8282. FAX: 802-656-8220.
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25
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Eckenroth BE, Rould MA, Hondal RJ, Everse SJ. Structural and biochemical studies reveal differences in the catalytic mechanisms of mammalian and Drosophila melanogaster thioredoxin reductases. Biochemistry 2007; 46:4694-705. [PMID: 17385893 PMCID: PMC3687216 DOI: 10.1021/bi602394p] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Thioredoxin reductase (TR) from Drosophila melanogaster (DmTR) is a member of the glutathione reductase (GR) family of pyridine nucleotide disulfide oxidoreductases and catalyzes the reduction of the redox-active disulfide bond of thioredoxin. DmTR is notable for having high catalytic activity without the presence of a selenocysteine (Sec) residue (which is essential for the mammalian thioredoxin reductases). We report here the X-ray crystal structure of DmTR at 2.4 A resolution (Rwork = 19.8%, Rfree = 24.7%) in which the enzyme was truncated to remove the C-terminal tripeptide sequence Cys-Cys-Ser. We also demonstrate that tetrapeptides equivalent to the oxidized C-terminal active sites of both mouse mitochondrial TR (mTR3) and DmTR are substrates for the truncated forms of both enzymes. This truncated enzyme/peptide substrate system examines the kinetics of the ring-opening step that occurs during the enzymatic cycle of TR. The ring-opening step is 300-500-fold slower when Sec is replaced with Cys in mTR3 when using this system. Conversely, when Cys is replaced with Sec in DmTR, the rate of ring opening is only moderately increased (5-36-fold). Structures of these tetrapeptides were oriented in the active site of both enzymes using oxidized glutathione bound to GR as a template. DmTR has a more open tetrapeptide binding pocket than the mouse enzyme and accommodates the peptide Ser-Cys-Cys-Ser(ox) in a cis conformation that allows for the protonation of the leaving-group Cys by His464', which helps to explain why this TR can function without the need for Sec. In contrast, mTR3 shows a narrower pocket. One possible result of this narrower interface is that the mammalian redox-active tetrapeptide Gly-Cys-Sec-Gly may adopt a trans conformation for a better fit. This places the Sec residue farther away from the protonating histidine residue, but the lower pKa of Sec in comparison to that of Cys eliminates the need for Sec to be protonated.
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Affiliation(s)
- Brian E. Eckenroth
- Department of Biochemistry, 89 Beaumont Ave, Given Building, Room C401, Burlington, VT 05405
| | - Mark A. Rould
- Department of Molecular Physiology and Biophysics, 312 Health Sciences Research Facility, Burlington, VT 05405
| | - Robert J. Hondal
- Department of Biochemistry, 89 Beaumont Ave, Given Building, Room C401, Burlington, VT 05405
- To whom correspondence should be addressed. Department of Biochemistry, University of Vermont, College of Medicine. 89 Beaumont Ave, Given Building, Room B413, Burlington, VT 05405. Tel: 802-656-8282. FAX: 802-656-8220.
| | - Stephen J. Everse
- Department of Biochemistry, 89 Beaumont Ave, Given Building, Room C401, Burlington, VT 05405
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