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Bodnar Y, Lillig CH. Cysteinyl and methionyl redox switches: Structural prerequisites and consequences. Redox Biol 2023; 65:102832. [PMID: 37536083 PMCID: PMC10412846 DOI: 10.1016/j.redox.2023.102832] [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: 07/12/2023] [Accepted: 07/27/2023] [Indexed: 08/05/2023] Open
Abstract
Redox modifications of specific cysteinyl and methionyl residues regulate key enzymes and signal-transducing proteins in various pathways. Here, we analyzed the effect of redox modifications on protein structure screening the RCSB protein data bank for oxidative modifications of proteins, i.e. protein disulfides, mixed disulfides with glutathione, cysteinyl sulfenic acids, cysteinyl S-nitrosylation, and methionyl sulfoxide residues. When available, these structures were compared to the structures of the same proteins in the reduced state with respect to both pre-requirements for the oxidative modifications as well as the structural consequences of the modifications. In general, the conformational changes induced by the redox modification are small, i.e. within the range of normal fluctuations. Some redox modifications, disulfides in particular, induces alterations in the electrostatic properties of the proteins. Solvent accessibility does not seem to be a strict pre-requirement for the redox modification of a particular residue. We identified an enrichment of certain other amino acid residues in the vicinity of the susceptible residues, for disulfide and sulfenic acid modifications, for instance, histidyl and tyrosyl residues. These motifs, as well as the specific features of the susceptible sulfur-containing amino acids, may become helpful for the prediction of redox modifications.
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Affiliation(s)
- Yana Bodnar
- Institut for Physics, University of Greifswald, Germany; Institute for Medical Biochemistry and Molecular Biology, University Medicine Greifswald, Germany
| | - Christopher Horst Lillig
- Institute for Medical Biochemistry and Molecular Biology, University Medicine Greifswald, Germany.
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2
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Kumar K, Shanmugam K, Abhimanyu S, Selvaraju S, Lakshmi Narayana BS, Sharanprasath RS, Kumar TN, Manikandan R, bala SH. Microbial isolation and characterization of arsenic degrading microbes from soil and its RAPD analysis for bioremediation. BIOMEDICAL AND BIOTECHNOLOGY RESEARCH JOURNAL (BBRJ) 2023. [DOI: 10.4103/bbrj.bbrj_330_22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/16/2023]
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3
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Ranganathan S, Sethi D, Kasivisweswaran S, Ramya L, Priyadarshini R, Yennamalli RM. Structural and functional mapping of ars gene cluster in Deinococcus indicus DR1. Comput Struct Biotechnol J 2022; 21:519-534. [PMID: 36618989 PMCID: PMC9807832 DOI: 10.1016/j.csbj.2022.12.015] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2022] [Revised: 12/08/2022] [Accepted: 12/08/2022] [Indexed: 12/14/2022] Open
Abstract
Deinococcus indicus DR1 is a novel Gram-negative bacterium, isolated from the Dadri wetlands in Uttar Pradesh, India. In addition to being radiation-resistant, the rod-shaped, red-pigmented organism shows extraordinary resistance to arsenic. The proteins of the corresponding ars gene cluster involved in arsenic extrusion in D. indicus DR1 have not yet been characterized. Additionally, how these proteins regulate each other providing arsenic resistance is still unclear. Here, we present a computational model of the operonic structure and the corresponding characterization of the six proteins of the ars gene cluster in D. indicus DR1. Additionally, we show the expression of the genes in the presence of arsenic using qRT-PCR. The ars gene cluster consists of two transcriptional regulators (ArsR1, ArsR2), two arsenate reductases (ArsC2, ArsC3), one metallophosphatase family protein (MPase), and a transmembrane arsenite efflux pump (ArsB). The transcriptional regulators are trans-acting repressors, and the reductases reduce arsenate (As5+) ions to arsenite (As3+) ions for favourable extrusion. The proteins modelled using RoseTTAFold, and their conformationally stable coordinates obtained after MD simulation indicate their various functional roles with respect to arsenic. Excluding ArsB, all the proteins belong to the α + β class of proteins. ArsB, being a membrane protein, is fully α-helical, with 12 transmembrane helices. The results show the degree of similarity or divergence of the mechanism utilized by these proteins of ars gene cluster in D. indicus DR1 to confer high levels of arsenic tolerance. This structural characterization study of the ars genes will enable new and deeper insights of arsenic tolerance.
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Affiliation(s)
- Shrivaishnavi Ranganathan
- Department of Biotechnology, School of Chemical and Biotechnology, SASTRA Deemed to be University, Thanjavur, Tamil Nadu 613401, India
| | - Deepa Sethi
- Department of Life Sciences, School of Natural Sciences, Shiv Nadar University, Gautam Buddha Nagar, Uttar Pradesh, India
| | - Sandhya Kasivisweswaran
- Department of Life Sciences, School of Natural Sciences, Shiv Nadar University, Gautam Buddha Nagar, Uttar Pradesh, India
| | - L. Ramya
- Computational and Molecular Biophysics Laboratory, School of Chemical and Biotechnology, SASTRA Deemed to be University, Thanjavur, Tamil Nadu 613401, India
| | - Richa Priyadarshini
- Department of Life Sciences, School of Natural Sciences, Shiv Nadar University, Gautam Buddha Nagar, Uttar Pradesh, India,Corresponding authors.
| | - Ragothaman M. Yennamalli
- Department of Bioinformatics, School of Chemical and Biotechnology, SASTRA Deemed to be University, Thanjavur, Tamil Nadu 613401, India,Corresponding authors.
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4
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Zuo D, Yin Y, Fang T, Jiang H, Ding J, Hu H, Wang S, Qi J, Tian M, Yu S. A homolog of low molecular weight protein tyrosine phosphatase isolated from Brucella melitensis displays an acidic dual specific phosphatase activity, nonessential for bacterial resistance to bactericidal factors and virulence. Comp Immunol Microbiol Infect Dis 2022; 90-91:101904. [DOI: 10.1016/j.cimid.2022.101904] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2022] [Revised: 10/27/2022] [Accepted: 11/01/2022] [Indexed: 11/06/2022]
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5
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Zhang W, Niu X, Ding J, Hu Y, Jin C. Intra- and inter-protein couplings of backbone motions underlie protein thiol-disulfide exchange cascade. Sci Rep 2018; 8:15448. [PMID: 30337655 PMCID: PMC6193951 DOI: 10.1038/s41598-018-33766-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2018] [Accepted: 10/06/2018] [Indexed: 11/09/2022] Open
Abstract
The thioredoxin (Trx)-coupled arsenate reductase (ArsC) is a family of enzymes that catalyzes the reduction of arsenate to arsenite in the arsenic detoxification pathway. The catalytic cycle involves a series of relayed intramolecular and intermolecular thiol-disulfide exchange reactions. Structures at different reaction stages have been determined, suggesting significant conformational fluctuations along the reaction pathway. Herein, we use two state-of-the-art NMR methods, the chemical exchange saturation transfer (CEST) and the CPMG-based relaxation dispersion (CPMG RD) experiments, to probe the conformational dynamics of B. subtilis ArsC in all reaction stages, namely the enzymatic active reduced state, the intra-molecular C10-C82 disulfide-bonded intermediate state, the inactive oxidized state, and the inter-molecular disulfide-bonded protein complex with Trx. Our results reveal highly rugged energy landscapes in the active reduced state, and suggest global collective motions in both the C10-C82 disulfide-bonded intermediate and the mixed-disulfide Trx-ArsC complex.
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Affiliation(s)
- Wenbo Zhang
- College of Life Sciences, Peking University, Beijing, 100871, China.,Beijing Nuclear Magnetic Resonance Center, Peking University, Beijing, 100871, China
| | - Xiaogang Niu
- College of Chemistry and Molecular Engineering, Peking University, Beijing, 100871, China.,Beijing Nuclear Magnetic Resonance Center, Peking University, Beijing, 100871, China
| | - Jienv Ding
- College of Life Sciences, Peking University, Beijing, 100871, China.,Beijing Nuclear Magnetic Resonance Center, Peking University, Beijing, 100871, China.,National Institutes of Health, DHHS 1050 Boyles Street, Frederick, MD, 21702, USA
| | - Yunfei Hu
- College of Chemistry and Molecular Engineering, Peking University, Beijing, 100871, China. .,Beijing Nuclear Magnetic Resonance Center, Peking University, Beijing, 100871, China. .,Medical College of Soochow University, Suzhou, 215123, China.
| | - Changwen Jin
- College of Life Sciences, Peking University, Beijing, 100871, China. .,College of Chemistry and Molecular Engineering, Peking University, Beijing, 100871, China. .,Beijing Nuclear Magnetic Resonance Center, Peking University, Beijing, 100871, China. .,Beijing National Laboratory for Molecular Sciences, Peking University, Beijing, 100871, China.
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6
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Song Y, Nikoloff JM, Fu G, Chen J, Li Q, Xie N, Zheng P, Sun J, Zhang D. Promoter Screening from Bacillus subtilis in Various Conditions Hunting for Synthetic Biology and Industrial Applications. PLoS One 2016; 11:e0158447. [PMID: 27380260 PMCID: PMC4933340 DOI: 10.1371/journal.pone.0158447] [Citation(s) in RCA: 51] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2016] [Accepted: 06/16/2016] [Indexed: 11/24/2022] Open
Abstract
The use of Bacillus subtilis in synthetic biology and metabolic engineering is highly desirable to take advantage of the unique metabolic pathways present in this organism. To do this, an evaluation of B. subtilis’ intrinsic biological parts is required to determine the best strategies to accurately regulate metabolic circuits and expression of target proteins. The strengths of promoter candidates were evaluated by measuring relative fluorescence units of a green fluorescent protein reporter, integrated into B. subtilis’ chromosome. A total of 84 predicted promoter sequences located upstream of different classes of proteins including heat shock proteins, cell-envelope proteins, and proteins resistant against toxic metals (based on similarity) and other kinds of genes were tested. The expression levels measured ranged from 0.0023 to 4.53-fold of the activity of the well-characterized strong promoter P43. No significant shifts were observed when strains, carrying different promoter candidates, were cultured at high temperature or in media with ethanol, but some strains showed increased activity when cultured under high osmotic pressure. Randomly selected promoter candidates were tested and found to activate transcription of thermostable β-galactosidase (bgaB) at a similar level, implying the ability of these sequences to function as promoter elements in multiple genetic contexts. In addition, selected promoters elevated the final production of both cytoplasmic bgaB and secreted protein α-amylase to about fourfold and twofold, respectively. The generated data allows a deeper understanding of B. subtilis’ metabolism and will facilitate future work to develop this organism for synthetic biology.
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Affiliation(s)
- Yafeng Song
- Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin 300308, P. R. China
- Key Laboratory of Systems Microbial Biotechnology, Chinese Academy of Sciences, Tianjin 300308, P. R. China
| | - Jonas M Nikoloff
- Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin 300308, P. R. China
| | - Gang Fu
- Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin 300308, P. R. China
- Key Laboratory of Systems Microbial Biotechnology, Chinese Academy of Sciences, Tianjin 300308, P. R. China
| | - Jingqi Chen
- Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin 300308, P. R. China
- Key Laboratory of Systems Microbial Biotechnology, Chinese Academy of Sciences, Tianjin 300308, P. R. China
| | - Qinggang Li
- Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin 300308, P. R. China
- Key Laboratory of Systems Microbial Biotechnology, Chinese Academy of Sciences, Tianjin 300308, P. R. China
| | - Nengzhong Xie
- National Engineering Research Center for Non-food Biorefinery, State Key Laboratory of Non-food Biomass Energy and Enzyme Technology, Nanning 5300074, P. R. China
- Guangxi Biomass Industrialization Engineering Institute, Guangxi Academy of Sciences, Nanning 530007, P. R. China
| | - Ping Zheng
- Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin 300308, P. R. China
- Key Laboratory of Systems Microbial Biotechnology, Chinese Academy of Sciences, Tianjin 300308, P. R. China
| | - Jibin Sun
- Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin 300308, P. R. China
- Key Laboratory of Systems Microbial Biotechnology, Chinese Academy of Sciences, Tianjin 300308, P. R. China
| | - Dawei Zhang
- Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin 300308, P. R. China
- Key Laboratory of Systems Microbial Biotechnology, Chinese Academy of Sciences, Tianjin 300308, P. R. China
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7
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Hu C, Yu C, Liu Y, Hou X, Liu X, Hu Y, Jin C. A Hybrid Mechanism for the Synechocystis Arsenate Reductase Revealed by Structural Snapshots during Arsenate Reduction. J Biol Chem 2015. [PMID: 26224634 DOI: 10.1074/jbc.m115.659896] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Evolution of enzymes plays a crucial role in obtaining new biological functions for all life forms. Arsenate reductases (ArsC) are several families of arsenic detoxification enzymes that reduce arsenate to arsenite, which can subsequently be extruded from cells by specific transporters. Among these, the Synechocystis ArsC (SynArsC) is structurally homologous to the well characterized thioredoxin (Trx)-coupled ArsC family but requires the glutaredoxin (Grx) system for its reactivation, therefore classified as a unique Trx/Grx-hybrid family. The detailed catalytic mechanism of SynArsC is unclear and how the "hybrid" mechanism evolved remains enigmatic. Herein, we report the molecular mechanism of SynArsC by biochemical and structural studies. Our work demonstrates that arsenate reduction is carried out via an intramolecular thiol-disulfide cascade similar to the Trx-coupled family, whereas the enzyme reactivation step is diverted to the coupling of the glutathione-Grx pathway due to the local structural difference. The current results support the hypothesis that SynArsC is likely a molecular fossil representing an intermediate stage during the evolution of the Trx-coupled ArsC family from the low molecular weight protein phosphotyrosine phosphatase (LMW-PTPase) family.
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Affiliation(s)
- Cuiyun Hu
- From the College of Chemistry and Molecular Engineering, Beijing Nuclear Magnetic Resonance Center
| | - Caifang Yu
- From the College of Chemistry and Molecular Engineering, Beijing Nuclear Magnetic Resonance Center
| | - Yanhua Liu
- From the College of Chemistry and Molecular Engineering
| | - Xianhui Hou
- From the College of Chemistry and Molecular Engineering, Beijing Nuclear Magnetic Resonance Center
| | - Xiaoyun Liu
- From the College of Chemistry and Molecular Engineering
| | - Yunfei Hu
- From the College of Chemistry and Molecular Engineering, Beijing Nuclear Magnetic Resonance Center,
| | - Changwen Jin
- From the College of Chemistry and Molecular Engineering, Beijing Nuclear Magnetic Resonance Center, College of Life Sciences, Beijing National Laboratory for Molecular Sciences, Peking University, Beijing 100871, China
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8
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ArsC3 from Desulfovibrio alaskensis G20, a cation and sulfate-independent highly efficient arsenate reductase. J Biol Inorg Chem 2014; 19:1277-85. [DOI: 10.1007/s00775-014-1184-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2014] [Accepted: 08/03/2014] [Indexed: 12/24/2022]
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9
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Tonks NK. Protein tyrosine phosphatases--from housekeeping enzymes to master regulators of signal transduction. FEBS J 2013; 280:346-78. [PMID: 23176256 DOI: 10.1111/febs.12077] [Citation(s) in RCA: 339] [Impact Index Per Article: 30.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2012] [Revised: 11/13/2012] [Accepted: 11/15/2012] [Indexed: 12/12/2022]
Abstract
There are many misconceptions surrounding the roles of protein phosphatases in the regulation of signal transduction, perhaps the most damaging of which is the erroneous view that these enzymes exert their effects merely as constitutively active housekeeping enzymes. On the contrary, the phosphatases are critical, specific regulators of signalling in their own right and serve an essential function, in a coordinated manner with the kinases, to determine the response to a physiological stimulus. This review is a personal perspective on the development of our understanding of the protein tyrosine phosphatase family of enzymes. I have discussed various aspects of the structure, regulation and function of the protein tyrosine phosphatase family, which I hope will illustrate the fundamental importance of these enzymes in the control of signal transduction.
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Affiliation(s)
- Nicholas K Tonks
- Cold Spring Harbor Laboratory, Cold Spring Harbor, NY 11724-2208, USA.
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10
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Villadangos AF, Van Belle K, Wahni K, Dufe VT, Freitas S, Nur H, De Galan S, Gil JA, Collet JF, Mateos LM, Messens J. Corynebacterium glutamicum survives arsenic stress with arsenate reductases coupled to two distinct redox mechanisms. Mol Microbiol 2011; 82:998-1014. [PMID: 22032722 DOI: 10.1111/j.1365-2958.2011.07882.x] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Arsenate reductases (ArsCs) evolved independently as a defence mechanism against toxic arsenate. In the genome of Corynebacterium glutamicum, there are two arsenic resistance operons (ars1 and ars2) and four potential genes coding for arsenate reductases (Cg_ArsC1, Cg_ArsC2, Cg_ArsC1' and Cg_ArsC4). Using knockout mutants, in vitro reconstitution of redox pathways, arsenic measurements and enzyme kinetics, we show that a single organism has two different classes of arsenate reductases. Cg_ArsC1 and Cg_ArsC2 are single-cysteine monomeric enzymes coupled to the mycothiol/mycoredoxin redox pathway using a mycothiol transferase mechanism. In contrast, Cg_ArsC1' is a three-cysteine containing homodimer that uses a reduction mechanism linked to the thioredoxin pathway with a k(cat)/K(M) value which is 10(3) times higher than the one of Cg_ArsC1 or Cg_ArsC2. Cg_ArsC1' is constitutively expressed at low levels using its own promoter site. It reduces arsenate to arsenite that can then induce the expression of Cg_ArsC1 and Cg_ArsC2. We also solved the X-ray structures of Cg_ArsC1' and Cg_ArsC2. Both enzymes have a typical low-molecular-weight protein tyrosine phosphatases-I fold with a conserved oxyanion binding site. Moreover, Cg_ArsC1' is unique in bearing an N-terminal three-helical bundle that interacts with the active site of the other chain in the dimeric interface.
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11
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Roos G, Geerlings P, Messens J. The conserved active site tryptophan of thioredoxin has no effect on its redox properties. Protein Sci 2010; 19:190-4. [PMID: 19902501 DOI: 10.1002/pro.269] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
In Staphylococcus aureus thioredoxin (Trx) it has been shown that mutation of the conserved active site tryptophan residue (Trp28) has a large effect on the protein stability, on the pKa of the nucleophilic cysteine and on the redox potential. Since these effects can either be due to the partially unfolding of the Trp28Ala mutant or to the absence of the indole side chain of Trp28 as possible interaction partner for the active site cysteines, the origin of the experimentally observed effects is not known and is beyond experimental approach. With theoretical pKa and density functional theory reactivity analysis on model systems where Trp28 has been replaced by an alanine within the structural environment of Trx it is shown that Trp28 does not affect the redox parameters of Trx. As such, the experimentally observed redox effects of the Trx W28A mutant might be due to structural changes induced by partial unfolding.
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Affiliation(s)
- Goedele Roos
- Department of Molecular and Cellular Interactions, VIB, Brussels 1050, Belgium.
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12
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Roy RK, Saha S. Studies of regioselectivity of large molecular systems using DFT based reactivity descriptors. ACTA ACUST UNITED AC 2010. [DOI: 10.1039/b811052m] [Citation(s) in RCA: 77] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Abstract
The dissociation mechanism of the thioredoxin (Trx) mixed disulfide complexes is unknown and has been debated for more than twenty years. Specifically, opposing arguments for the activation of the nucleophilic cysteine as a thiolate during the dissociation of the complex have been put forward. As a key model, the complex between Trx and its endogenous substrate, arsenate reductase (ArsC), was used. In this structure, a Cys29Trx-Cys89ArsC intermediate disulfide is formed by the nucleophilic attack of Cys29Trx on the exposed Cys82ArsC-Cys89ArsC in oxidized ArsC. With theoretical reactivity analysis, molecular dynamics simulations, and biochemical complex formation experiments with Cys-mutants, Trx mixed disulfide dissociation was studied. We observed that the conformational changes around the intermediate disulfide bring Cys32Trx in contact with Cys29Trx. Cys32Trx is activated for its nucleophilic attack by hydrogen bonds, and Cys32Trx is found to be more reactive than Cys82ArsC. Additionally, Cys32Trx directs its nucleophilic attack on the more susceptible Cys29Trx and not on Cys89ArsC. This multidisciplinary approach provides fresh insights into a universal thiol/disulfide exchange reaction mechanism that results in reduced substrate and oxidized Trx. Thioredoxins are found in all types of cells and control several essential functions of life, including promotion of cell growth, inhibition of apoptosis, and modulation of inflammation. Thioredoxin has two ‘free’ cysteines in its active site, which are used to break disulfide bonds in oxidized substrate proteins. In the first step, an intermediate thioredoxin-protein complex is formed, which is broken in the second step, releasing the substrate protein in its reduced state. In other words, the disulfide is being transferred from the substrate protein to thioredoxin, or the electrons coming from thioredoxin are shuttled to the protein substrate. The exact reaction mechanism, i.e., the detailed succession of steps in which the reaction takes place, of how this mixed disulfide is broken is not known and has been debated over the last twenty years. With a multidisciplinary approach, combining computational and experimental work, we provide fresh insights into how conformational changes activate the catalytic cysteines with which this universal reduction mechanism is completed with the correct regioselectivity. This work illustrates the strengths of computational approaches in probing phenomena which are otherwise very difficult to investigate experimentally.
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The glutathione/glutaredoxin system is essential for arsenate reduction in Synechocystis sp. strain PCC 6803. J Bacteriol 2009; 191:3534-43. [PMID: 19304854 DOI: 10.1128/jb.01798-08] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Arsenic resistance in Synechocystis sp. strain PCC 6803 is mediated by an operon of three genes in which arsC codes for an arsenate reductase with unique characteristics. Here we describe the identification of two additional and nearly identical genes coding for arsenate reductases in Synechocystis sp. strain PCC 6803, which we have designed arsI1 and arsI2, and the biochemical characterization of both ArsC (arsenate reductase) and ArsI. Functional analysis of single, double, and triple mutants shows that both ArsI enzymes are active arsenate reductases but that their roles in arsenate resistance are essential only in the absence of ArsC. Based on its biochemical properties, ArsC belongs to a family that, though related to thioredoxin-dependent arsenate reductases, uses the glutathione/glutaredoxin system for reduction, whereas ArsI belongs to the previously known glutaredoxin-dependent family. We have also analyzed the role in arsenate resistance of the three glutaredoxins present in Synechocystis sp. strain PCC 6803 both in vitro and in vivo. Only the dithiolic glutaredoxins, GrxA (glutaredoxin A) and GrxB (glutaredoxin B), are able to donate electrons to both types of reductases in vitro, while GrxC (glutaredoxin C), a monothiolic glutaredoxin, is unable to donate electrons to either type. Analysis of glutaredoxin mutant strains revealed that only those lacking the grxA gene have impaired arsenic resistance.
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15
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Li Y, Hu Y, Zhang X, Xu H, Lescop E, Xia B, Jin C. Conformational Fluctuations Coupled to the Thiol-Disulfide Transfer between Thioredoxin and Arsenate Reductase in Bacillus subtilis. J Biol Chem 2007; 282:11078-83. [PMID: 17303556 DOI: 10.1074/jbc.m700970200] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Arsenic compounds commonly exist in nature and are toxic to nearly all kinds of life forms, which directed the evolution of enzymes in many organisms for arsenic detoxification. In bacteria, the thioredoxin-coupled arsenate reductase catalyzes the reduction of arsenate to arsenite by intramolecular thiol-disulfide cascade. The oxidized arsenate reductase ArsC is subsequently regenerated by thioredoxin through an intermolecular thiol-disulfide exchange process. The solution structure of the Bacillus subtilis thioredoxin-arsenate reductase complex represents the transiently formed intermediate during the intermolecular thiol-disulfide exchange reaction. A comparison of the complex structure with that of thioredoxin and arsenate reductase proteins in redox states showed substantial conformational changes coupled to the reaction process, with arsenate reductase, especially, adopting an "intermediate" conformation in the complex. Our current studies provide novel insights into understanding the reaction mechanisms of the thioredoxin-arsenate reductase pathway.
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Affiliation(s)
- You Li
- Beijing Nuclear Magnetic Resonance Center, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China
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16
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Messens J, Silver S. Arsenate Reduction: Thiol Cascade Chemistry with Convergent Evolution. J Mol Biol 2006; 362:1-17. [PMID: 16905151 DOI: 10.1016/j.jmb.2006.07.002] [Citation(s) in RCA: 117] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2006] [Revised: 07/04/2006] [Accepted: 07/06/2006] [Indexed: 12/01/2022]
Abstract
The frequent abundance of arsenic in the environment has guided the evolution of enzymes for the reduction of arsenate. The arsenate reductases (ArsC) from different sources have unrelated sequences and structural folds, and can be divided into different classes on the basis of their structures, reduction mechanisms and the locations of catalytic cysteine residues. The thioredoxin-coupled arsenate reductase class is represented by Staphylococcus aureus pI258 ArsC and Bacillus subtilis ArsC. The ArsC from Escherichia coli plasmid R773 and the eukaryotic ACR2p reductase from Saccharomyces cerevisiae represent two distinct glutaredoxin-linked ArsC classes. All are small cytoplasmic redox enzymes that reduce arsenate to arsenite by the sequential involvement of three different thiolate nucleophiles that function as a redox cascade. In contrast, the ArrAB complex is a bacterial heterodimeric periplasmic or a surface-anchored arsenate reductase that functions as a terminal electron acceptor and transfers electrons from the membrane respiratory chain to arsenate. Finally, the less well documented arsenate reductase activity of the monomeric arsenic(III) methylase, which is an S-adenosylmethionine (AdoMet)-dependent methyltransferase. After each oxidative methylation cycle and before the next methylation step, As(V) is reduced to As(III). Methylation by this enzyme is also considered an arsenic-resistance mechanism for bacteria, fungi and mammals.
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Affiliation(s)
- Joris Messens
- Brussels Center for Redox Biology, Department of Molecular and Cellular Interactions, Vlaams interuniversitair Instituut voor Biotechnologie (VIB) at the Vrije Universiteit Brussel (VUB), Pleinlaan 2, 1050 Brussel, Belgium.
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17
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Roos G, Buts L, Van Belle K, Brosens E, Geerlings P, Loris R, Wyns L, Messens J. Interplay between ion binding and catalysis in the thioredoxin-coupled arsenate reductase family. J Mol Biol 2006; 360:826-38. [PMID: 16797027 DOI: 10.1016/j.jmb.2006.05.054] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2006] [Revised: 05/18/2006] [Accepted: 05/22/2006] [Indexed: 11/25/2022]
Abstract
In the thioredoxin (Trx)-coupled arsenate reductase family, arsenate reductase from Staphylococcus aureus plasmid pI258 (Sa_ArsC) and from Bacillus subtilis (Bs_ArsC) are structurally related detoxification enzymes. Catalysis of the reduction of arsenate to arsenite involves a P-loop (Cys10Thr11Gly12Asn13Ser14Cys15Arg16) structural motif and a disulphide cascade between three conserved cysteine residues (Cys10, Cys82 and Cys89). For its activity, Sa_ArsC benefits from the binding of tetrahedral oxyanions in the P-loop active site and from the binding of potassium in a specific cation-binding site. In contrast, the steady-state kinetic parameters of Bs_ArsC are not affected by sulphate or potassium. The commonly occurring mutation of a histidine (H62), located about 6 A from the potassium-binding site in Sa_ArsC, to a glutamine uncouples the kinetic dependency on potassium. In addition, the binding affinity for potassium is affected by the presence of a lysine (K33) or an aspartic acid (D33) in combination with two negative charges (D30 and E31) on the surface of Trx-coupled arsenate reductases. In the P-loop of the Trx-coupled arsenate reductase family, the peptide bond between Gly12 and Asn13 can adopt two distinct conformations. The unique geometry of the P-loop with Asn13 in beta conformation, which is not observed in structurally related LMW PTPases, is stabilized by tetrahedral oxyanions and decreases the pK(a) value of Cys10 and Cys82. Tetrahedral oxyanions stabilize the P-loop in its catalytically most active form, which might explain the observed increase in k(cat) value for Sa_ArsC. Therefore, a subtle interplay of potassium and sulphate dictates the kinetics of Trx-coupled arsenate reductases.
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Affiliation(s)
- Goedele Roos
- Laboratorium voor Ultrastructuur, Department of Molecular and Cellular Interactions, Vlaams Interuniversitair Instituut voor Biotechnologie (VIB), Vrije Universiteit Brussel (VUB), Pleinlaan 2, 1050 Brussels, Belgium
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