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Gouveia AG, Salgueiro BA, Ranmar DO, Antunes WDT, Kirchweger P, Golani O, Wolf SG, Elbaum M, Matias PM, Romão CV. Unraveling the multifaceted resilience of arsenic resistant bacterium Deinococcus indicus. Front Microbiol 2023; 14:1240798. [PMID: 37692390 PMCID: PMC10483234 DOI: 10.3389/fmicb.2023.1240798] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2023] [Accepted: 08/09/2023] [Indexed: 09/12/2023] Open
Abstract
Arsenic (As) is a toxic heavy metal widely found in the environment that severely undermines the integrity of water resources. Bioremediation of toxic compounds is an appellative sustainable technology with a balanced cost-effective setup. To pave the way for the potential use of Deinococcus indicus, an arsenic resistant bacterium, as a platform for arsenic bioremediation, an extensive characterization of its resistance to cellular insults is paramount. A comparative analysis of D. indicus cells grown in two rich nutrient media conditions (M53 and TGY) revealed distinct resistance patterns when cells are subjected to stress via UV-C and methyl viologen (MV). Cells grown in M53 demonstrated higher resistance to both UV-C and MV. Moreover, cells grow to higher density upon exposure to 25 mM As(V) in M53 in comparison with TGY. This analysis is pivotal for the culture of microbial species in batch culture bioreactors for bioremediation purposes. We also demonstrate for the first time the presence of polyphosphate granules in D. indicus which are also found in a few Deinococcus species. To extend our analysis, we also characterized DiArsC2 (arsenate reductase) involved in arsenic detoxification and structurally determined different states, revealing the structural evidence for a catalytic cysteine triple redox system. These results contribute for our understanding into the D. indicus resistance mechanism against stress conditions.
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Affiliation(s)
- André G. Gouveia
- Instituto de Tecnologia Química e Biológica António Xavier (ITQB NOVA), Universidade Nova de Lisboa, Oeiras, Portugal
| | - Bruno A. Salgueiro
- Instituto de Tecnologia Química e Biológica António Xavier (ITQB NOVA), Universidade Nova de Lisboa, Oeiras, Portugal
| | - Dean O. Ranmar
- Department of Life Sciences Core Facilities, Weizmann Institute of Science, Rehovot, Israel
| | - Wilson D. T. Antunes
- Instituto Universitário Militar, Centro de Investigação da Academia Militar (CINAMIL), Unidade Militar Laboratorial de Defesa Biológica e Química (UMLDBQ), Lisbon, Portugal
| | - Peter Kirchweger
- Department of Chemical and Biological Physics, Weizmann Institute of Science, Rehovot, Israel
| | - Ofra Golani
- Department of Life Sciences Core Facilities, Weizmann Institute of Science, Rehovot, Israel
| | - Sharon G. Wolf
- Department of Chemical Research Support, Weizmann Institute of Science, Rehovot, Israel
| | - Michael Elbaum
- Department of Chemical and Biological Physics, Weizmann Institute of Science, Rehovot, Israel
| | - Pedro M. Matias
- Instituto de Tecnologia Química e Biológica António Xavier (ITQB NOVA), Universidade Nova de Lisboa, Oeiras, Portugal
- Instituto de Biologia Experimental e Tecnológica (iBET), Oeiras, Portugal
| | - Célia V. Romão
- Instituto de Tecnologia Química e Biológica António Xavier (ITQB NOVA), Universidade Nova de Lisboa, Oeiras, Portugal
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2
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Mohsin H, Shafique M, Zaid M, Rehman Y. Microbial biochemical pathways of arsenic biotransformation and their application for bioremediation. Folia Microbiol (Praha) 2023:10.1007/s12223-023-01068-6. [PMID: 37326815 DOI: 10.1007/s12223-023-01068-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2022] [Accepted: 05/19/2023] [Indexed: 06/17/2023]
Abstract
Arsenic is a ubiquitous toxic metalloid, the concentration of which is beyond WHO safe drinking water standards in many areas of the world, owing to many natural and anthropogenic activities. Long-term exposure to arsenic proves lethal for plants, humans, animals, and even microbial communities in the environment. Various sustainable strategies have been developed to mitigate the harmful effects of arsenic which include several chemical and physical methods, however, bioremediation has proved to be an eco-friendly and inexpensive technique with promising results. Many microbes and plant species are known for arsenic biotransformation and detoxification. Arsenic bioremediation involves different pathways such as uptake, accumulation, reduction, oxidation, methylation, and demethylation. Each of these pathways has a certain set of genes and proteins to carry out the mechanism of arsenic biotransformation. Based on these mechanisms, various studies have been conducted for arsenic detoxification and removal. Genes specific for these pathways have also been cloned in several microorganisms to enhance arsenic bioremediation. This review discusses different biochemical pathways and the associated genes which play important roles in arsenic redox reactions, resistance, methylation/demethylation, and accumulation. Based on these mechanisms, new methods can be developed for effective arsenic bioremediation.
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Affiliation(s)
- Hareem Mohsin
- Department of Life Sciences, School of Science, University of Management and Technology, Lahore, Pakistan
| | - Maria Shafique
- Institute of Microbiology and Molecular Genetics, University of the Punjab, Quaid-e-Azam Campus, Lahore, Pakistan
| | - Muhammad Zaid
- Department of Life Sciences, School of Science, University of Management and Technology, Lahore, Pakistan
| | - Yasir Rehman
- Department of Life Sciences, School of Science, University of Management and Technology, Lahore, Pakistan.
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Gao P, Zhang X, Huang X, Chen Z, Marietou A, Holmkvist L, Qu L, Finster K, Gong X. Genomic insight of sulfate reducing bacterial genus Desulfofaba reveals their metabolic versatility in biogeochemical cycling. BMC Genomics 2023; 24:209. [PMID: 37076818 PMCID: PMC10116758 DOI: 10.1186/s12864-023-09297-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2022] [Accepted: 04/04/2023] [Indexed: 04/21/2023] Open
Abstract
BACKGROUND Sulfate-reducing bacteria (SRB) drive the ocean sulfur and carbon cycling. They constitute a diverse phylogenetic and physiological group and are widely distributed in anoxic marine environments. From a physiological viewpoint, SRB's can be categorized as complete or incomplete oxidizers, meaning that they either oxidize their carbon substrate completely to CO2 or to a stoichiometric mix of CO2 and acetate. Members of Desulfofabaceae family are incomplete oxidizers, and within that family, Desulfofaba is the only genus with three isolates that are classified into three species. Previous physiological experiments revealed their capability of respiring oxygen. RESULTS Here, we sequenced the genomes of three isolates in Desulfofaba genus and reported on a genomic comparison of the three species to reveal their metabolic potentials. Based on their genomic contents, they all could oxidize propionate to acetate and CO2. We confirmed their phylogenetic position as incomplete oxidizers based on dissimilatory sulfate reductase (DsrAB) phylogeny. We found the complete pathway for dissimilatory sulfate reduction, but also different key genes for nitrogen cycling, including nitrogen fixation, assimilatory nitrate/nitrite reduction, and hydroxylamine reduction to nitrous oxide. Their genomes also contain genes that allow them to cope with oxygen and oxidative stress. They have genes that encode for diverse central metabolisms for utilizing different substrates with the potential for more strains to be isolated in the future, yet their distribution is limited. CONCLUSIONS Results based on marker gene search and curated metagenome assembled genomes search suggest a limited environmental distribution of this genus. Our results reveal a large metabolic versatility within the Desulfofaba genus which establishes their importance in biogeochemical cycling of carbon in their respective habitats, as well as in the support of the entire microbial community through releasing easily degraded organic matters.
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Affiliation(s)
- Ping Gao
- Key Laboratory of Marine Eco-Environmental Science and Technology, First Institute of Oceanography, Ministry of Natural Resources (MNR), 266061, Qingdao, PR China
- Laboratory for Marine Fisheries Science and Food Production Processes, Pilot National Laboratory for Marine Science and Technology, 266237, Qingdao, PR China
| | - Xiaoting Zhang
- Institute of Marine Science and Technology, Shandong University, 266237, Qingdao, PR China
| | - Xiaomei Huang
- Institute of Marine Science and Technology, Shandong University, 266237, Qingdao, PR China
| | - Zhiyi Chen
- Institute of Marine Science and Technology, Shandong University, 266237, Qingdao, PR China
| | - Angeliki Marietou
- Section for Microbiology, Department of Biology, Aarhus University, 8000, Aarhus, Denmark
- Department of Biological and Chemical Engineering, Aarhus University, 8000, Aarhus, Denmark
| | - Lars Holmkvist
- Section for Microbiology, Department of Biology, Aarhus University, 8000, Aarhus, Denmark
| | - Lingyun Qu
- Key Laboratory of Marine Eco-Environmental Science and Technology, First Institute of Oceanography, Ministry of Natural Resources (MNR), 266061, Qingdao, PR China
- Laboratory for Marine Fisheries Science and Food Production Processes, Pilot National Laboratory for Marine Science and Technology, 266237, Qingdao, PR China
| | - Kai Finster
- Section for Microbiology, Department of Biology, Aarhus University, 8000, Aarhus, Denmark
- Stellar Astrophysics Center, Department of Physics and Astronomy, Aarhus University, 8000, Aarhus, Denmark
| | - Xianzhe Gong
- Institute of Marine Science and Technology, Shandong University, 266237, Qingdao, PR China.
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4
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Ke T, Zhang D, Guo H, Xiu W, Zhao Y. Geogenic arsenic and arsenotrophic microbiome in groundwater from the Hetao Basin. THE SCIENCE OF THE TOTAL ENVIRONMENT 2022; 852:158549. [PMID: 36075436 DOI: 10.1016/j.scitotenv.2022.158549] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/03/2022] [Revised: 08/28/2022] [Accepted: 09/01/2022] [Indexed: 06/15/2023]
Abstract
High arsenic (As) in groundwater is an environmental issue of global concern, which is closely related to microbe-mediated As biogeochemical cycling. However, the distribution of genes related to As cycling and underlying microbial As biogeochemical processes in high As groundwater remain elusive. Hence, we profiled the As cycling genes (arsC, arrA, and aioA genes) and indigenous microbial communities in groundwater from a typical high As area, the Hetao Basin from China, using amplicon sequencing and qPCR techniques. Here, we revealed the significant difference in microbial community structure between low As groundwater samples (LG) and high As groundwater samples (HG). Acinetobacter, Thiovirga, Hydrogenophaga, and Sulfurimonas were dominant in LG, while Aquabcterium, Acinetobacter, Sphingomonas, Pseudomonas, Desulfomicrobium, Hydrogenophaga, and Nitrospira were predominant in HG. Shannon and Chao indices of the microbial communities in HG were significantly higher than those of in LG. Alpha diversity and abundance of arsC and arrA genes were higher than those of aioA genes. The significant positive correlation was uncovered between the abundances of arsC and aioA genes, suggesting the cooccurrence of As functional genes in groundwater. Sphingopyxis, Agrobacterium, Klebsiella, Hoeflea, and Aeromonas represented the dominant taxa within the As (V) reducers communities. Distance-based redundancy analysis showed that ORP, pH, Astot, Mn, and DOC were the key factors shaping the diverse microbial populations, while ORP, S2-, As(III), Fe(II), NH4+, pH, Mn, SO42-, As(V), temperature, and P as the main drivers affecting arsenotrophic microbiota. This work provides an insight into microbial communities linked to As biogeochemical processes in high As groundwater, playing a fundamental role in groundwater As cycling.
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Affiliation(s)
- Tiantian Ke
- Ministry of Education, Key Laboratory of Groundwater Circulation and Environmental Evolution, School of Water Resources and Environment, China University of Geosciences (Beijing), Beijing, China; State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences (Beijing), Beijing, China
| | - Di Zhang
- Ministry of Education, Key Laboratory of Groundwater Circulation and Environmental Evolution, School of Water Resources and Environment, China University of Geosciences (Beijing), Beijing, China; State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences (Beijing), Beijing, China
| | - Huaming Guo
- Ministry of Education, Key Laboratory of Groundwater Circulation and Environmental Evolution, School of Water Resources and Environment, China University of Geosciences (Beijing), Beijing, China; State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences (Beijing), Beijing, China.
| | - Wei Xiu
- State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences (Beijing), Beijing, China
| | - Yi Zhao
- Ministry of Education, Key Laboratory of Groundwater Circulation and Environmental Evolution, School of Water Resources and Environment, China University of Geosciences (Beijing), Beijing, China
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5
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Biochemical, molecular and in silico characterization of arsenate reductase from Bacillus thuringiensis KPWP1 tolerant to salt, arsenic and a wide range of pH. Arch Microbiol 2021; 204:46. [DOI: 10.1007/s00203-021-02660-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2021] [Revised: 10/08/2021] [Accepted: 10/11/2021] [Indexed: 01/03/2023]
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6
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Rosen MR, Leuthaeuser JB, Parish CA, Fetrow JS. Isofunctional Clustering and Conformational Analysis of the Arsenate Reductase Superfamily Reveals Nine Distinct Clusters. Biochemistry 2020; 59:4262-4284. [PMID: 33135415 DOI: 10.1021/acs.biochem.0c00651] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Arsenate reductase (ArsC) is a superfamily of enzymes that reduce arsenate. Due to active site similarities, some ArsC can function as low-molecular weight protein tyrosine phosphatases (LMW-PTPs). Broad superfamily classifications align with redox partners (Trx- or Grx-linked). To understand this superfamily's mechanistic diversity, the ArsC superfamily is classified on the basis of active site features utilizing the tools TuLIP (two-level iterative clustering process) and autoMISST (automated multilevel iterative sequence searching technique). This approach identified nine functionally relevant (perhaps isofunctional) protein groups. Five groups exhibit distinct ArsC mechanisms. Three are Grx-linked: group 4AA (classical ArsC), group 3AAA (YffB-like), and group 5BAA. Two are Trx-linked: groups 6AAAAA and 7AAAAAAAA. One is an Spx-like transcriptional regulatory group, group 5AAA. Three are potential LMW-PTP groups: groups 7BAAAA, and 7AAAABAA, which have not been previously identified, and the well-studied LMW-PTP family group 8AAA. Molecular dynamics simulations were utilized to explore functional site details. In several families, we confirm and add detail to literature-based mechanistic information. Mechanistic roles are hypothesized for conserved active site residues in several families. In three families, simulations of the unliganded structure sample specific conformational ensembles, which are proposed to represent either a more ligand-binding-competent conformation or a pathway toward a more binding-competent state; these active sites may be designed to traverse high-energy barriers to the lower-energy conformations necessary to more readily bind ligands. This more detailed biochemical understanding of ArsC and ArsC-like PTP mechanisms opens possibilities for further understanding of arsenate bioremediation and the LMW-PTP mechanism.
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Affiliation(s)
- Mikaela R Rosen
- Department of Chemistry, Gottwald Center for the Sciences, University of Richmond, Richmond, Virginia 23713, United States
| | - Janelle B Leuthaeuser
- Department of Chemistry, Gottwald Center for the Sciences, University of Richmond, Richmond, Virginia 23713, United States
| | - Carol A Parish
- Department of Chemistry, Gottwald Center for the Sciences, University of Richmond, Richmond, Virginia 23713, United States
| | - Jacquelyn S Fetrow
- Department of Chemistry, Gottwald Center for the Sciences, University of Richmond, Richmond, Virginia 23713, United States
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7
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Banaś AM, Bocian-Ostrzycka KM, Jagusztyn-Krynicka EK. Engineering of the Dsb (disulfide bond) proteins - contribution towards understanding their mechanism of action and their applications in biotechnology and medicine. Crit Rev Microbiol 2019; 45:433-450. [PMID: 31190593 DOI: 10.1080/1040841x.2019.1622509] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
The Dsb protein family in prokaryotes catalyzes the generation of disulfide bonds between thiol groups of cysteine residues in nascent proteins, ensuring their proper three-dimensional structure; these bonds are crucial for protein stability and function. The first Dsb protein, Escherichia coli DsbA, was described in 1991. Since then, many details of the bond-formation process have been described through microbiological, biochemical, biophysical and bioinformatics strategies. Research with the model microorganism E. coli and many other bacterial species revealed an enormous diversity of bond-formation mechanisms. Research using Dsb protein engineering has significantly helped to reveal details of the disulfide bond formation. The first part of this review presents the research that led to understanding the mechanism of action of DsbA proteins, which directly transfer their own disulfide into target proteins. The second part concentrates on the mechanism of electron transport through the cell cytoplasmic membrane. Third and lastly, the review discusses the contribution of this research towards new antibacterial agents.
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Affiliation(s)
- Anna Marta Banaś
- Department of Bacterial Genetics, Institute of Microbiology, Faculty of Biology, University of Warsaw , Miecznikowa 1 , Warsaw , Poland
| | - Katarzyna Marta Bocian-Ostrzycka
- Department of Bacterial Genetics, Institute of Microbiology, Faculty of Biology, University of Warsaw , Miecznikowa 1 , Warsaw , Poland
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8
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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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Beavers WN, Skaar EP. Neutrophil-generated oxidative stress and protein damage in Staphylococcus aureus. Pathog Dis 2016; 74:ftw060. [PMID: 27354296 DOI: 10.1093/femspd/ftw060] [Citation(s) in RCA: 83] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/08/2016] [Indexed: 01/06/2023] Open
Abstract
Staphylococcus aureus is a ubiquitous, versatile and dangerous pathogen. It colonizes over 30% of the human population, and is one of the leading causes of death by an infectious agent. During S. aureus colonization and invasion, leukocytes are recruited to the site of infection. To combat S. aureus, leukocytes generate an arsenal of reactive species including superoxide, hydrogen peroxide, nitric oxide and hypohalous acids that modify and inactivate cellular macromolecules, resulting in growth defects or death. When S. aureus colonization cannot be cleared by the immune system, antibiotic treatment is necessary and can be effective. Yet, this organism quickly gains resistance to each new antibiotic it encounters. Therefore, it is in the interest of human health to acquire a deeper understanding of how S. aureus evades killing by the immune system. Advances in this field will have implications for the design of future S. aureus treatments that complement and assist the host immune response. In that regard, this review focuses on how S. aureus avoids host-generated oxidative stress, and discusses the mechanisms used by S. aureus to survive oxidative damage including antioxidants, direct repair of damaged proteins, sensing oxidant stress and transcriptional changes. This review will elucidate areas for studies to identify and validate future antimicrobial targets.
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Affiliation(s)
- William N Beavers
- Department of Pathology, Microbiology and Immunology, U.S. Department of Veteran Affairs, Vanderbilt Institute of Chemical Biology, Vanderbilt University School of Medicine, 1161 21st Avenue South, Medical Center North, Nashville, TN 37232, USA
| | - Eric P Skaar
- Department of Pathology, Microbiology and Immunology, U.S. Department of Veteran Affairs, Vanderbilt Institute of Chemical Biology, Vanderbilt University School of Medicine, 1161 21st Avenue South, Medical Center North, Nashville, TN 37232, USA Tennessee Valley Healthcare System, U.S. Department of Veteran Affairs, Vanderbilt Institute of Chemical Biology, Vanderbilt University School of Medicine, 1161 21st Avenue South, Nashville, TN 37232, USA
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10
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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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11
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Mori Y, Kimura Y. Myxococcus xanthus low-molecular-weight protein tyrosine phosphatase homolog, ArsA, possesses arsenate reductase activity. J Biosci Bioeng 2014; 118:10-3. [PMID: 24503422 DOI: 10.1016/j.jbiosc.2013.12.013] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2013] [Revised: 12/13/2013] [Accepted: 12/18/2013] [Indexed: 11/25/2022]
Abstract
Myxococcus xanthus MXAN_0575, ArsA, exhibited sequence homology to low-molecular-weight protein tyrosine phosphatases (LMWPTPs) and arsenate reductases. ArsA exhibited weak phosphatase activity toward p-nitrophenyl phosphate, and high arsenate reductase activity, suggesting that ArsA may play a role in arsenate reductase, but not LMWPTP.
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Affiliation(s)
- Yumi Mori
- Department of Applied Biological Science, Faculty of Agriculture, Kagawa University, Miki-cho, Kagawa 761-0795, Japan
| | - Yoshio Kimura
- Department of Applied Biological Science, Faculty of Agriculture, Kagawa University, Miki-cho, Kagawa 761-0795, Japan.
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12
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Pandey S, Shrivastava AK, Rai R, Rai LC. Molecular characterization of Alr1105 a novel arsenate reductase of the diazotrophic cyanobacterium Anabaena sp. PCC7120 and decoding its role in abiotic stress management in Escherichia coli. PLANT MOLECULAR BIOLOGY 2013; 83:417-432. [PMID: 23836391 DOI: 10.1007/s11103-013-0100-x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/16/2013] [Accepted: 06/22/2013] [Indexed: 06/02/2023]
Abstract
This paper constitutes the first report on the Alr1105 of Anabaena sp. PCC7120 which functions as arsenate reductase and phosphatase and offers tolerance against oxidative and other abiotic stresses in the alr1105 transformed Escherichia coli. The bonafide of 40.8 kDa recombinant GST+Alr1105 fusion protein was confirmed by immunoblotting. The purified Alr1105 protein (mw 14.8 kDa) possessed strong arsenate reductase (Km 16.0 ± 1.2 mM and Vmax 5.6 ± 0.31 μmol min⁻¹ mg protein⁻¹) and phosphatase activity (Km 27.38 ± 3.1 mM and Vmax 0.077 ± 0.005 μmol min⁻¹ mg protein⁻¹) at an optimum temperature 37 °C and 6.5 pH. Native Alr1105 was found as a monomeric protein in contrast to its homologous Synechocystis ArsC protein. Expression of Alr1105 enhanced the arsenic tolerance in the arsenate reductase mutant E. coli WC3110 (∆arsC) and rendered better growth than the wild type W3110 up to 40 mM As (V). Notwithstanding above, the recombinant E. coli strain when exposed to CdCl₂, ZnSO₄, NiCl₂, CoCl₂, CuCl₂, heat, UV-B and carbofuron showed increase in growth over the wild type and mutant E. coli transformed with the empty vector. Furthermore, an enhanced growth of the recombinant E. coli in the presence of oxidative stress producing chemicals (MV, PMS and H₂O₂), suggested its protective role against these stresses. Appreciable expression of alr1105 gene as measured by qRT-PCR at different time points under selected stresses reconfirmed its role in stress tolerance. Thus the Alr1105 of Anabaena sp. PCC7120 functions as an arsenate reductase and possess novel properties different from the arsenate reductases known so far.
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Affiliation(s)
- Sarita Pandey
- Molecular Biology Section, Laboratory of Algal Biology, Center of Advanced Study in Botany, Banaras Hindu University, Varanasi, 221005, India
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13
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Affiliation(s)
- Shengwen Shen
- Department
of Laboratory Medicine
and Pathology, 10-102 Clinical Sciences Building, University
of Alberta, Edmonton, Alberta, Canada, T6G 2G3
| | - Xing-Fang Li
- Department
of Laboratory Medicine
and Pathology, 10-102 Clinical Sciences Building, University
of Alberta, Edmonton, Alberta, Canada, T6G 2G3
| | - William R. Cullen
- Department of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver,
British Columbia, Canada, V6T 1Z1
| | - Michael Weinfeld
- Department of Oncology, Cross
Cancer Institute, University of Alberta, 11560 University Avenue, Edmonton, Alberta, Canada, T6G 1Z2
| | - X. Chris Le
- Department
of Laboratory Medicine
and Pathology, 10-102 Clinical Sciences Building, University
of Alberta, Edmonton, Alberta, Canada, T6G 2G3
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14
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Dhuldhaj UP, Yadav IC, Singh S, Sharma NK. Microbial interactions in the arsenic cycle: adoptive strategies and applications in environmental management. REVIEWS OF ENVIRONMENTAL CONTAMINATION AND TOXICOLOGY 2013; 224:1-38. [PMID: 23232917 DOI: 10.1007/978-1-4614-5882-1_1] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Arsenic (As) is a nonessential element that is often present in plants and in other organisms. However, it is one of the most hazardous of toxic elements globally. In many parts of the world, arsenic contamination in groundwater is a serious and continuing threat to human health. Microbes play an important role in regulating the environmental fate of arsenic. Different microbial processes influence the biogeochemical cycling of arsenic in ways that affect the accumulation of different arsenic species in various ecosystem compartments. For example, in soil, there are bacteria that methylate arsenite to trimethylarsine gas, thereby releasing arsenic to the atmosphere.In marine ecosystems, microbes exist that can convert inorganic arsenicals to organic arsenicals (e.g., di- and tri-methylated arsenic derivatives, arsenocholine,arsenobetaine, arsenosugars, arsenolipids). The organo arsenicals are further metabolized to complete the arsenic cycle.Microbes have developed various strategies that enable them to tolerate arsenic and to survive in arsenic-rich environments. Such strategies include As exclusion from cells by establishing permeability barrier, intra- and extracellular sequestration,active efflux pumps, enzymatic reduction, and reduction in the sensitivity of cellular targets. These strategies are used either singly or in combination. In bacteria,the genes for arsenic resistance/detoxification are encoded by the arsenic resistance operons (ars operon).In this review, we have addressed and emphasized the impact of different microbial processes (e.g., arsenite oxidation, cytoplasmic arsenate reduction, respiratory arsenate reduction, arsenite methylation) on the arsenic cycle. Microbes are the only life forms reported to exist in heavy arsenic-contaminated environments. Therefore,an understanding of the strategies adopted by microbes to cope with arsenic stress is important in managing such arsenic-contaminated sites. Further future insights into the different microbial genes/proteins that are involved in arsenic resistance may also be useful for developing arsenic resistant crop plants.
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Jain S, Saluja B, Gupta A, Marla SS, Goel R. Validation of Arsenic Resistance in Bacillus cereus Strain AG27 by Comparative Protein Modeling of arsC Gene Product. Protein J 2011; 30:91-101. [DOI: 10.1007/s10930-011-9305-5] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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16
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Zafra O, Fraile S, Gutiérrez C, Haro A, Páez-Espino AD, Jiménez JI, de Lorenzo V. Monitoring biodegradative enzymes with nanobodies raised in Camelus dromedarius with mixtures of catabolic proteins. Environ Microbiol 2011; 13:960-74. [DOI: 10.1111/j.1462-2920.2010.02401.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
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Bhattacharjee H, Sheng J, Ajees AA, Mukhopadhyay R, Rosen BP. Adventitious arsenate reductase activity of the catalytic domain of the human Cdc25B and Cdc25C phosphatases. Biochemistry 2010; 49:802-9. [PMID: 20025242 DOI: 10.1021/bi9019127] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
A number of eukaryotic enzymes that function as arsenate reductases are homologues of the catalytic domain of the human Cdc25 phosphatase. For example, the Leishmania major enzyme LmACR2 is both a phosphatase and an arsenate reductase, and its structure bears similarity to the structure of the catalytic domain of human Cdc25 phosphatase. These reductases contain an active site C-X(5)-R signature motif, where C is the catalytic cysteine, the five X residues form a phosphate binding loop, and R is a highly conserved arginine, which is also present in human Cdc25 phosphatases. We therefore investigated the possibility that the three human Cdc25 isoforms might have adventitious arsenate reductase activity. The sequences for the catalytic domains of Cdc25A, -B, and -C were cloned individually into a prokaryotic expression vector, and their gene products were purified from a bacterial host using nickel affinity chromatography. While each of the three Cdc25 catalytic domains exhibited phosphatase activity, arsenate reductase activity was observed only with Cdc25B and -C. These two enzymes reduced inorganic arsenate but not methylated pentavalent arsenicals. Alteration of either the cysteine and arginine residues of the Cys-X(5)-Arg motif led to the loss of both reductase and phosphatase activities. Our observations suggest that Cdc25B and -C may adventitiously reduce arsenate to the more toxic arsenite and may also provide a framework for identifying other human protein tyrosine phosphatases containing the active site Cys-X(5)-Arg loop that might moonlight as arsenate reductases.
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Affiliation(s)
- Hiranmoy Bhattacharjee
- Department of Cellular Biology and Pharmacology, Florida International University, Herbert Wertheim College of Medicine, Miami, Florida 33199, USA.
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18
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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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19
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Roos G, Geerlings P, Messens J. Enzymatic catalysis: the emerging role of conceptual density functional theory. J Phys Chem B 2009; 113:13465-75. [PMID: 19754087 DOI: 10.1021/jp9034584] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Experimentalists and quantum chemists are living in a different world. A wealth of theoretical enzymology-related publications is hardly known by experimentalists, and vice versa. Our aim is to bring both worlds together and to show the powerful possibilities of a multidisciplinary approach to study subtle details of complicated enzymatic processes to a broad readership. MD simulations and QM/MM approaches often focus on the calculation of reaction paths based on activation energies, which is a time-consuming task. A valuable alternative is the reactivity descriptors founded in conceptual DFT like softness, electrophilicity, and the Fukui function, which describe the kinetic aspects of a reaction in terms of the response to perturbations in N and/or upsilon(r), typical for a chemical reaction, of the reagents in the ground state. As such, the relative energies at the beginning of the reaction predict a sequence of activation energies only based on the properties of the reactants (Figure 5 ). In 2003, Geerlings et al. published a key review giving a detailed description of the principles and concepts of conceptual DFT and highlighting its success to study generalized acid/base reactions including addition, substitution, and elimination reactions. Since the time that this review appeared, conceptual DFT has proven its strength in literally hundreds of papers with application to organic and inorganic reactions. Its role in unravelling enzymatic reaction mechanisms, in handling experimentally difficult accessible biochemical problems, and in the interpretation of biochemical experimental observations is emerging and very promising.
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Affiliation(s)
- Goedele Roos
- Department of Molecular and Cellular Interactions, VIB, Pleinlaan 2, 1050 Brussels, Belgium.
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20
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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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Abstract
For many years, oxidative thiol modifications in cytosolic proteins were largely disregarded as in vitro artifacts, and considered unlikely to play significant roles within the reducing environment of the cell. Recent developments in in vivo thiol trapping technology combined with mass spectrometric analysis have now provided convincing evidence that thiol-based redox switches are used as molecular tools in many proteins to regulate their activity in response to reactive oxygen and nitrogen species. Reversible oxidative thiol modifications have been found to modulate the function of proteins involved in many different pathways, starting from gene transcription, translation and protein folding, to metabolism, signal transduction, and ultimately apoptosis. This review will focus on three well-characterized eukaryotic proteins that use thiol-based redox switches to influence gene transcription, metabolism, and signal transduction. The transcription factor Yap1p is a good illustration of how oxidative modifications affect the function of a protein without changing its activity. We use glyeraldehyde-3-phosphate dehydrogenase to demonstrate how thiol modification of an active site cysteine re-routes metabolic pathways and converts a metabolic enzyme into a pro-apoptotic factor. Finally, we introduce the redox-sensitive protein tyrosine phosphatase PTP1B to illustrate that reversibility is one of the fundamental aspects of redox-regulation.
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Affiliation(s)
- Nicolas Brandes
- Department of Molecular, Cellular and Developmental Biology, University of Michigan, Ann Arbor, Michigan 48109, USA
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22
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Ordóñez E, Van Belle K, Roos G, De Galan S, Letek M, Gil JA, Wyns L, Mateos LM, Messens J. Arsenate reductase, mycothiol, and mycoredoxin concert thiol/disulfide exchange. J Biol Chem 2009; 284:15107-16. [PMID: 19286650 DOI: 10.1074/jbc.m900877200] [Citation(s) in RCA: 81] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We identified the first enzymes that use mycothiol and mycoredoxin in a thiol/disulfide redox cascade. The enzymes are two arsenate reductases from Corynebacterium glutamicum (Cg_ArsC1 and Cg_ArsC2), which play a key role in the defense against arsenate. In vivo knockouts showed that the genes for Cg_ArsC1 and Cg_ArsC2 and those of the enzymes of the mycothiol biosynthesis pathway confer arsenate resistance. With steady-state kinetics, arsenite analysis, and theoretical reactivity analysis, we unraveled the catalytic mechanism for the reduction of arsenate to arsenite in C. glutamicum. The active site thiolate in Cg_ArsCs facilitates adduct formation between arsenate and mycothiol. Mycoredoxin, a redox enzyme for which the function was never shown before, reduces the thiol-arseno bond and forms arsenite and a mycothiol-mycoredoxin mixed disulfide. A second molecule of mycothiol recycles mycoredoxin and forms mycothione that, in its turn, is reduced by the NADPH-dependent mycothione reductase. Cg_ArsCs show a low specificity constant of approximately 5 m(-1) s(-1), typically for a thiol/disulfide cascade with nucleophiles on three different molecules. With the in vitro reconstitution of this novel electron transfer pathway, we have paved the way for the study of redox mechanisms in actinobacteria.
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Affiliation(s)
- Efrén Ordóñez
- Department of Molecular Biology, Area of Microbiology, University of León, 24071 León, Spain
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23
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Garcia-Pino A, Martinez-Rodriguez S, Wahni K, Wyns L, Loris R, Messens J. Coupling of domain swapping to kinetic stability in a thioredoxin mutant. J Mol Biol 2008; 385:1590-9. [PMID: 19071139 DOI: 10.1016/j.jmb.2008.11.040] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2008] [Revised: 11/08/2008] [Accepted: 11/19/2008] [Indexed: 10/21/2022]
Abstract
The thioredoxin (Trx) fold is a small monomeric domain that is ubiquitous in redox-active enzymes. Trxs are characterized by a typical WCGPC active-site sequence motif. A single active-site mutation of the tryptophan to an alanine in Staphylococcus aureus Trx converts the oxidized protein into a biologically inactive domain-swapped dimer. While the monomeric protein unfolds reversibly in a two-state manner, the oxidized dimeric form is kinetically stable and converts to the monomeric form upon refolding. After reduction, the half-life of the dimer decreases many orders of magnitude to approximately 4.3 h, indicating that the active-site disulfide between Cys29 and Cys32 is an important determinant for the kinetics of unfolding. We propose kinetic stability as a possible evolutionary strategy in the evolution of multimeric proteins from their monomeric ancestors by domain swapping, which, for this biologically inactive Trx mutant, turned out to be an evolutionary dead end.
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Affiliation(s)
- Abel Garcia-Pino
- Department of Molecular and Cellular Interactions, Vlaams Instituut voor Biotechnologie, Brussels, Belgium
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24
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Lu M, Wang H, Wang Z, Li XF, Le XC. Identification of reactive cysteines in a protein using arsenic labeling and collision-induced dissociation tandem mass spectrometry. J Proteome Res 2008; 7:3080-90. [PMID: 18613716 DOI: 10.1021/pr700662y] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Trivalent arsenicals have high affinity for thiols (such as free cysteines) in proteins. We describe here the use of this property to develop a collision-induced dissociation (CID) tandem mass spectrometry (MS/MS) technique for the identification of reactive cysteines in proteins. A trivalent arsenic species, dimethylarsinous acid (DMA (III)), with a residue mass (103.9607) and mass defect distinct from the normal 20 amino acids, was used to selectively label reactive cysteine residues in proteins. The CID fragment ions of the arsenic-labeled sequences shifted away from the more abundant normal fragments that would otherwise overlap with the ions of interest. Along with the internal and immonium ions, the arsenic-labeled fragment ions served as MS/MS signatures for identification of the binding sites and for assessment of the relative reactivity of individual cysteine residues in a protein. Using this method, we have identified two highly reactive binding sites in rat hemoglobin (Hb): Cys-13alpha and Cys-125beta. Cys-13alpha was bound to DMA (III) in the Hb of rats fed with arsenic, and this binding was responsible for arsenic accumulation in rat blood, while Cys-125beta was found to bind to glutathione in rat blood. This study revealed the relative reactivity of the cysteines in rat Hb in the following decreasing order: Cys-13alpha >> Cys-111alpha > Cys-104alpha and Cys-13alpha >> Cys-125beta > Cys-93beta. Arsenic-labeling is easy and fast for identification of active binding sites without enzymatic digestion and acid hydrolysis, and useful for characterization and identification of metal binding sites in other proteins.
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Affiliation(s)
- Meiling Lu
- Department of Chemistry and Laboratory Medicine and Pathology, University of Alberta, Edmonton, Alberta, Canada
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Brenchley R, Tariq H, McElhinney H, Szöor B, Huxley-Jones J, Stevens R, Matthews K, Tabernero L. The TriTryp phosphatome: analysis of the protein phosphatase catalytic domains. BMC Genomics 2007; 8:434. [PMID: 18039372 PMCID: PMC2175518 DOI: 10.1186/1471-2164-8-434] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2007] [Accepted: 11/26/2007] [Indexed: 01/21/2023] Open
Abstract
Background The genomes of the three parasitic protozoa Trypanosoma cruzi, Trypanosoma brucei and Leishmania major are the main subject of this study. These parasites are responsible for devastating human diseases known as Chagas disease, African sleeping sickness and cutaneous Leishmaniasis, respectively, that affect millions of people in the developing world. The prevalence of these neglected diseases results from a combination of poverty, inadequate prevention and difficult treatment. Protein phosphorylation is an important mechanism of controlling the development of these kinetoplastids. With the aim to further our knowledge of the biology of these organisms we present a characterisation of the phosphatase complement (phosphatome) of the three parasites. Results An ontology-based scan of the three genomes was used to identify 86 phosphatase catalytic domains in T. cruzi, 78 in T. brucei, and 88 in L. major. We found interesting differences with other eukaryotic genomes, such as the low proportion of tyrosine phosphatases and the expansion of the serine/threonine phosphatase family. Additionally, a large number of atypical protein phosphatases were identified in these species, representing more than one third of the total phosphatase complement. Most of the atypical phosphatases belong to the dual-specificity phosphatase (DSP) family and show considerable divergence from classic DSPs in both the domain organisation and sequence features. Conclusion The analysis of the phosphatome of the three kinetoplastids indicates that they possess orthologues to many of the phosphatases reported in other eukaryotes, including humans. However, novel domain architectures and unusual combinations of accessory domains, suggest distinct functional roles for several of the kinetoplastid phosphatases, which await further experimental exploration. These distinct traits may be exploited in the selection of suitable new targets for drug development to prevent transmission and spread of the diseases, taking advantage of the already extensive knowledge on protein phosphatase inhibitors.
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Affiliation(s)
- Rachel Brenchley
- Faculty of Life Sciences, Michael Smith, University of Manchester, M13 9PT, UK.
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26
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Roos G, Garcia-Pino A, Van Belle K, Brosens E, Wahni K, Vandenbussche G, Wyns L, Loris R, Messens J. The Conserved Active Site Proline Determines the Reducing Power of Staphylococcus aureus Thioredoxin. J Mol Biol 2007; 368:800-11. [PMID: 17368484 DOI: 10.1016/j.jmb.2007.02.045] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2006] [Revised: 02/10/2007] [Accepted: 02/13/2007] [Indexed: 11/15/2022]
Abstract
Nature uses thioredoxin-like folds in several disulfide bond oxidoreductases. Each of them has a typical active site Cys-X-X-Cys sequence motif, the hallmark of thioredoxin being Trp-Cys-Gly-Pro-Cys. The intriguing role of the highly conserved proline in the ubiquitous reducing agent thioredoxin was studied by site-specific mutagenesis of Staphylococcus aureus thioredoxin (Sa_Trx). We present X-ray structures, redox potential, pK(a), steady-state kinetic parameters, and thermodynamic stabilities. By replacing the central proline to a threonine/serine, no extra hydrogen bonds with the sulphur of the nucleophilic cysteine are introduced. The only structural difference is that the immediate chemical surrounding of the nucleophilic cysteine becomes more hydrophilic. The pK(a) value of the nucleophilic cysteine decreases with approximately one pH unit and its redox potential increases with 30 mV. Thioredoxin becomes more oxidizing and the efficiency to catalyse substrate reduction (k(cat)/K(M)) decreases sevenfold relative to wild-type Sa_Trx. The oxidized form of wild-type Sa_Trx is far more stable than the reduced form over the whole temperature range. The driving force to reduce substrate proteins is the relative stability of the oxidized versus the reduced form Delta(T(1/2))(ox/red). This driving force is decreased in the Sa_Trx P31T mutant. Delta(T(1/2))(ox/red) drops from 15.5 degrees C (wild-type) to 5.8 degrees C (P31T mutant). In conclusion, the active site proline in thioredoxin determines the driving potential for substrate reduction.
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Affiliation(s)
- Goedele Roos
- Department of Molecular and Cellular Interactions, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, Belgium
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27
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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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28
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Schnell S, Hanson SM. A test for measuring the effects of enzyme inactivation. Biophys Chem 2007; 125:269-74. [PMID: 17011111 DOI: 10.1016/j.bpc.2006.08.010] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2006] [Revised: 08/28/2006] [Accepted: 08/29/2006] [Indexed: 10/24/2022]
Abstract
In the single-enzyme, single-substrate reaction with non-mechanism-based enzyme inactivation, the formation of the product and inactivation of the enzyme occur independently. For this reaction, we show that the steady-state hypothesis is applicable even when degradation of the enzyme occurs. An equation for the rate of product formation has been derived and it shows Michaelis-Menten kinetics with an apparent Michaelis-Menten constant K(M)(app)=K(M)+K(delta) where K(delta) is the enzyme inactivation constant. Use of a Lineweaver-Burk plot yields values for K(M)(app), which can be used to estimate K(delta) and, consequently, the degree of enzyme inactivation in a particular experiment. We employ this methodology to estimate the inactivation constant for the arsenate reductase catalyzed production of arsenite with appreciable enzyme inactivation.
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Affiliation(s)
- Santiago Schnell
- Complex Systems Group, Indiana University School of Informatics, 1900 East Tenth Street, Bloomington, IN 47406, USA.
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29
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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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Guo X, Li Y, Peng K, Hu Y, Li C, Xia B, Jin C. Solution structures and backbone dynamics of arsenate reductase from Bacillus subtilis: reversible conformational switch associated with arsenate reduction. J Biol Chem 2005; 280:39601-8. [PMID: 16192272 DOI: 10.1074/jbc.m508132200] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Arsenate reductase encoded by the chromosomal arsC gene in Bacillus subtilis catalyzes the intracellular reduction of arsenate to arsenite, which is then extruded from cells through an efficient and specific transport system. Herein, we present the solution structures and backbone dynamics of both the reduced and oxidized forms of arsenate reductase from B. subtilis. The overall structures of both forms are similar to those of bovine low molecular weight protein-tyrosine phosphatase and arsenate reductase from Staphylococcus aureus. However, several features of the tertiary structure and mobility are notably different between the reduced and oxidized forms of B. subtilis arsenate reductase, particularly in the P-loop region and the segment Cys(82)-Cys(89). The backbone dynamics results demonstrated that the reduced form of arsenate reductase undergoes millisecond conformational changes in the functional P-loop and Cys(82)-Cys(89), which may facilitate the formation of covalent intermediates and subsequent reduction of arsenate. In the oxidized form, Cys(82)-Cys(89) shows motional flexibility on both picosecond-to-nanosecond and possibly millisecond time scales, which may facilitate the reduction of the oxidized enzyme by thioredoxin to regenerate the active enzyme. Overall, the internal dynamics and static structures of the enzyme provide insights into the molecular mechanism of arsenate reduction, especially the reversible conformational switch and changes in internal motions associated with the catalytic reaction.
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Affiliation(s)
- Xianrong Guo
- Beijing Nuclear Magnetic Resonance Center and the College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China
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31
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Silver S, Phung LT. Genes and enzymes involved in bacterial oxidation and reduction of inorganic arsenic. Appl Environ Microbiol 2005; 71:599-608. [PMID: 15691908 PMCID: PMC546828 DOI: 10.1128/aem.71.2.599-608.2005] [Citation(s) in RCA: 338] [Impact Index Per Article: 17.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Affiliation(s)
- Simon Silver
- Department of Microbiology and Immunology, MC790, University of Illinois, 835 S. Wolcott Ave., Chicago, IL 60612-7344, USA.
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Li K, Hein S, Zou W, Klug G. The glutathione-glutaredoxin system in Rhodobacter capsulatus: part of a complex regulatory network controlling defense against oxidative stress. J Bacteriol 2004; 186:6800-8. [PMID: 15466032 PMCID: PMC522184 DOI: 10.1128/jb.186.20.6800-6808.2004] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2004] [Accepted: 07/23/2004] [Indexed: 11/20/2022] Open
Abstract
Mutants with defects in components of the glutathione-glutaredoxin (GSH/Grx) system of Rhodobacter capsulatus were constructed to study its role in defense against oxidative stress and the redox-dependent formation of photosynthetic complexes. The lack of the glutaredoxin 3 gene (grxC) or the glutathione synthetase B gene (gshB) resulted in lower growth rates under aerobic conditions and higher sensitivity to oxidative stress, confirming the role of the GSH/Grx system in oxidative stress defense. Both mutants are highly sensitive to disulfide stress, indicating a major contribution of the GSH/Grx system to the thiol-disulfide redox buffer in the cytoplasm. Like mutations in the thioredoxin system, mutations in the GSH/Grx system affected the formation of photosynthetic complexes, which is redox dependent in R. capsulatus. Expression of the genes grxC, gshB, grxA for glutaredoxin 1, and gorA for glutathione reductase, all encoding components of the GSH/Grx system, was not induced by oxidative stress. Other genes, for which a role in oxidative stress was established in Escherichia coli, acnA, fpr, fur, and katG, were strongly induced by oxidative stress in R. capsulatus. Mutations in the grxC, and/or gshB, and/or trxC (thioredoxin 2) genes affected expression of these genes, indicating an interplay of the different defense systems against oxidative stress. The OxyR and the SoxRS regulons control the expression of many genes involved in oxidative stress defense in E. coli in response to H2O2 and superoxide, respectively. Our data and the available genome sequence of R. capsulatus suggest that a SoxRS system is lacking but an alternative superoxide specific regulator exists in R. capsulatus. While the expression of gorA and grxA is regulated by H2O2 in E. coli this is not the case in R. capsulatus, indicating that the OxyR regulons of these two species are significantly different.
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Affiliation(s)
- Kuanyu Li
- Institut für Mikrobiologie und Molekularbiologie, Heinrich-Buff-Ring 26-32, 35392 Giessen, Germany
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33
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Messens J, Van Molle I, Vanhaesebrouck P, Limbourg M, Van Belle K, Wahni K, Martins JC, Loris R, Wyns L. How thioredoxin can reduce a buried disulphide bond. J Mol Biol 2004; 339:527-37. [PMID: 15147840 DOI: 10.1016/j.jmb.2004.04.016] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2004] [Accepted: 04/02/2004] [Indexed: 11/18/2022]
Abstract
We present a study of the interaction between thioredoxin and the model enzyme pI258 arsenate reductase (ArsC) from Staphylococcus aureus. ArsC catalyses the reduction of arsenate to arsenite. Three redox active cysteine residues (Cys10, Cys82 and Cys89) are involved. After a single catalytic arsenate reduction event, oxidized ArsC exposes a disulphide bridge between Cys82 and Cys89 on a looped-out redox helix. Thioredoxin converts oxidized ArsC back towards its initial reduced state. In the absence of a reducing environment, the active-site P-loop of ArsC is blocked by the formation of a second disulphide bridge (Cys10-Cys15). While fully reduced ArsC can be recovered by exposing this double oxidized ArsC to thioredoxin, the P-loop disulphide bridge is itself inaccessible to thioredoxin. To reduce this buried Cys10-Cys15 disulphide-bridge in double oxidized ArsC, an intra-molecular Cys10-Cys82 disulphide switch connects the thioredoxin mediated inter-protein thiol-disulphide transfer to the buried disulphide. In the initial step of the reduction mechanism, thioredoxin appears to be selective for oxidized ArsC that requires the redox helix to be looped out for its interaction. The formation of a buried disulphide bridge in the active-site might function as protection against irreversible oxidation of the nucleophilic cysteine, a characteristic that has also been observed in the structurally similar low molecular weight tyrosine phosphatase.
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Affiliation(s)
- Joris Messens
- Laboratorium voor Ultrastructuur, Vlaams Interuniversitair Instituut voor Biotechnologie (VIB), Vrije Universiteit Brussel, Pleinlaan 2, B-1050 Brussels, Belgium.
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34
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Li R, Haile JD, Kennelly PJ. An arsenate reductase from Synechocystis sp. strain PCC 6803 exhibits a novel combination of catalytic characteristics. J Bacteriol 2004; 185:6780-9. [PMID: 14617642 PMCID: PMC262706 DOI: 10.1128/jb.185.23.6780-6789.2003] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The deduced protein product of open reading frame slr0946 from Synechocystis sp. strain PCC 6803, SynArsC, contains the conserved sequence features of the enzyme superfamily that includes the low-molecular-weight protein-tyrosine phosphatases and the Staphylococcus aureus pI258 ArsC arsenate reductase. The recombinant protein product of slr0946, rSynArsC, exhibited vigorous arsenate reductase activity (V(max) = 3.1 micro mol/min. mg), as well as weak phosphatase activity toward p-nitrophenyl phosphate (V(max) = 0.08 micro mol/min. mg) indicative of its phosphohydrolytic ancestry. pI258 ArsC from S. aureus is the prototype of one of three distinct families of detoxifying arsenate reductases. The prototypes of the others are Acr2p from Saccharomyces cerevisiae and R773 ArsC from Escherichia coli. All three have converged upon catalytic mechanisms involving an arsenocysteine intermediate. While SynArsC is homologous to pI258 ArsC, its catalytic mechanism exhibited a unique combination of features. rSynArsC employed glutathione and glutaredoxin as the source of reducing equivalents, like Acr2p and R773 ArsC, rather than thioredoxin, as does the S. aureus enzyme. As postulated for Acr2p and R773 ArsC, rSynArsC formed a covalent complex with glutathione in an arsenate-dependent manner. rSynArsC contains three essential cysteine residues like pI258 ArsC, whereas the yeast and E. coli enzymes require only one cysteine for catalysis. As in the S. aureus enzyme, these "extra" cysteines apparently shuttle a disulfide bond to the enzyme's surface to render it accessible for reduction. SynArsC and pI258 ArsC thus appear to represent alternative branches in the evolution of their shared phosphohydrolytic ancestor into an agent of arsenic detoxification.
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Affiliation(s)
- Renhui Li
- Department of Biochemistry, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061, USA
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Messens J, Martins JC, Zegers I, Van Belle K, Brosens E, Wyns L. Purification of an oxidation-sensitive enzyme, pI258 arsenate reductase from Staphylococcus aureus. J Chromatogr B Analyt Technol Biomed Life Sci 2003; 790:217-27. [PMID: 12767334 DOI: 10.1016/s1570-0232(03)00079-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Arsenate reductase (ArsC) from Staphylococcus aureus pI258 is extremely sensitive to oxidative inactivation. The presence of oxidized ArsC forms was not that critical for NMR, but kinetics and crystallization required an extra reversed-phase purification to increase sample homogeneity. The salt ions observed in the X-ray electron density of ArsC were investigated. Carbonate was found to have the lowest dissociation constant for activation (K(a)=1.1 mM) and potassium was stabilizing ArsC (DeltaT(m)=+6.2 degrees C). Also due to the use of these salt ions, the final yield of the purification had improved with a factor of four, i.e. 73 mg/l culture.
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Affiliation(s)
- Joris Messens
- Dienst Ultrastructuur, Vlaams Interuniversitair Instituut voor Biotechnologie (VIB), Vrije Universiteit Brussel, Paardenstraat 65, B-1640, Sint-Genesius-Rode, Belgium.
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36
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Abstract
All living organisms have systems for arsenic detoxification. The common themes are (a) uptake of As(V) in the form of arsenate by phosphate transporters, (b) uptake of As(III) in the form of arsenite by aquaglyceroporins, (c) reduction of As(V) to As(III) by arsenate reductases, and (d) extrusion or sequestration of As(III). While the overall schemes for arsenic resistance are similar in prokaryotes and eukaryotes, some of the specific proteins are the products of separate evolutionary pathways.
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Affiliation(s)
- Barry P Rosen
- Department of Biochemistry and Molecular Biology, Wayne State University, School of Medicine, 48201, Detroit, MI, USA.
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Mukhopadhyay R, Rosen BP, Phung LT, Silver S. Microbial arsenic: from geocycles to genes and enzymes. FEMS Microbiol Rev 2002; 26:311-25. [PMID: 12165430 DOI: 10.1111/j.1574-6976.2002.tb00617.x] [Citation(s) in RCA: 380] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
Arsenic compounds have been abundant at near toxic levels in the environment since the origin of life. In response, microbes have evolved mechanisms for arsenic resistance and enzymes that oxidize As(III) to As(V) or reduce As(V) to As(III). Formation and degradation of organoarsenicals, for example methylarsenic compounds, occur. There is a global arsenic geocycle, where microbial metabolism and mobilization (or immobilization) are important processes. Recent progress in studies of the ars operon (conferring resistance to As(III) and As(V)) in many bacterial types (and related systems in Archaea and yeast) and new understanding of arsenite oxidation and arsenate reduction by respiratory-chain-linked enzyme complexes has been substantial. The DNA sequencing and protein crystal structures have established the convergent evolution of three classes of arsenate reductases (that is classes of arsenate reductases are not of common evolutionary origin). Proposed reaction mechanisms in each case involve three cysteine thiols and S-As bond intermediates, so convergent evolution to similar mechanisms has taken place.
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Affiliation(s)
- Rita Mukhopadhyay
- Department of Biochemistry and Molecular Biology, Wayne State University School of Medicine, Detroit, MI 48201, USA
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Messens J, Martins JC, Van Belle K, Brosens E, Desmyter A, De Gieter M, Wieruszeski JM, Willem R, Wyns L, Zegers I. All intermediates of the arsenate reductase mechanism, including an intramolecular dynamic disulfide cascade. Proc Natl Acad Sci U S A 2002; 99:8506-11. [PMID: 12072565 PMCID: PMC124290 DOI: 10.1073/pnas.132142799] [Citation(s) in RCA: 64] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2002] [Indexed: 11/18/2022] Open
Abstract
The mechanism of pI258 arsenate reductase (ArsC) catalyzed arsenate reduction, involving its P-loop structural motif and three redox active cysteines, has been unraveled. All essential intermediates are visualized with x-ray crystallography, and NMR is used to map dynamic regions in a key disulfide intermediate. Steady-state kinetics of ArsC mutants gives a view of the crucial residues for catalysis. ArsC combines a phosphatase-like nucleophilic displacement reaction with a unique intramolecular disulfide bond cascade. Within this cascade, the formation of a disulfide bond triggers a reversible "conformational switch" that transfers the oxidative equivalents to the surface of the protein, while releasing the reduced substrate.
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Affiliation(s)
- Joris Messens
- Dienst Ultrastructuur, Vlaams interuniversitair Instituut voor Biotechnologie, Vrije Universiteit Brussel, Paardenstraat 65, 1640 St. Genesius-Rode, Belgium.
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Bentley R, Chasteen TG. Microbial methylation of metalloids: arsenic, antimony, and bismuth. Microbiol Mol Biol Rev 2002; 66:250-71. [PMID: 12040126 PMCID: PMC120786 DOI: 10.1128/mmbr.66.2.250-271.2002] [Citation(s) in RCA: 299] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
A significant 19th century public health problem was that the inhabitants of many houses containing wallpaper decorated with green arsenical pigments experienced illness and death. The problem was caused by certain fungi that grew in the presence of inorganic arsenic to form a toxic, garlic-odored gas. The garlic odor was actually put to use in a very delicate microbiological test for arsenic. In 1933, the gas was shown to be trimethylarsine. It was not until 1971 that arsenic methylation by bacteria was demonstrated. Further research in biomethylation has been facilitated by the development of delicate techniques for the determination of arsenic species. As described in this review, many microorganisms (bacteria, fungi, and yeasts) and animals are now known to biomethylate arsenic, forming both volatile (e.g., methylarsines) and nonvolatile (e.g., methylarsonic acid and dimethylarsinic acid) compounds. The enzymatic mechanisms for this biomethylation are discussed. The microbial conversion of sodium arsenate to trimethylarsine proceeds by alternate reduction and methylation steps, with S-adenosylmethionine as the usual methyl donor. Thiols have important roles in the reductions. In anaerobic bacteria, methylcobalamin may be the donor. The other metalloid elements of the periodic table group 15, antimony and bismuth, also undergo biomethylation to some extent. Trimethylstibine formation by microorganisms is now well established, but this process apparently does not occur in animals. Formation of trimethylbismuth by microorganisms has been reported in a few cases. Microbial methylation plays important roles in the biogeochemical cycling of these metalloid elements and possibly in their detoxification. The wheel has come full circle, and public health considerations are again important.
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Affiliation(s)
- Ronald Bentley
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA.
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Dao-Thi MH, Charlier D, Loris R, Maes D, Messens J, Wyns L, Backmann J. Intricate interactions within the ccd plasmid addiction system. J Biol Chem 2002; 277:3733-42. [PMID: 11741897 DOI: 10.1074/jbc.m105505200] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The ccd addiction system plays a crucial role in the stable maintenance of the Escherichia coli F plasmid. It codes for a stable toxin (CcdB) and a less stable antidote (CcdA). Both are expressed at low levels during normal cell growth. Upon plasmid loss, CcdB outlives CcdA and kills the cell by poisoning gyrase. The interactions between CcdB, CcdA, and its promoter DNA were analyzed. In solution, the CcdA-CcdB interaction is complex, leading to various complexes with different stoichiometry. CcdA has two binding sites for CcdB and vice versa, permitting soluble hexamer formation but also causing precipitation, especially at CcdA:CcdB ratios close to one. CcdA alone, but not CcdB, binds to promoter DNA with high on and off rates. The presence of CcdB enhances the affinity and the specificity of CcdA-DNA binding and results in a stable CcdA*CcdB*DNA complex with a CcdA:CcdB ratio of one. This (CcdA(2)CcdB(2))(n) complex has multiple DNA-binding sites and spirals around the 120-bp promoter region.
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Affiliation(s)
- Minh-Hoa Dao-Thi
- Vlaams interuniversitair Instituut voor Biotechnologie, Vrije Universiteit Brussel, Laboratorium voor Ultrastructuur, Paardenstraat 65, B-1640 Sint-Genesius-Rode, Belgium
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Bennett MS, Guan Z, Laurberg M, Su XD. Bacillus subtilis arsenate reductase is structurally and functionally similar to low molecular weight protein tyrosine phosphatases. Proc Natl Acad Sci U S A 2001; 98:13577-82. [PMID: 11698660 PMCID: PMC61083 DOI: 10.1073/pnas.241397198] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2001] [Indexed: 01/30/2023] Open
Abstract
Arsenate is an abundant oxyanion that, because of its ability to mimic the phosphate group, is toxic to cells. Arsenate reductase (EC; encoded by the arsC gene in bacteria) participates to achieve arsenate resistance in both prokaryotes and yeast by reducing arsenate to arsenite; the arsenite is then exported by a specific transporter. The crystal structure of Bacillus subtilis arsenate reductase in the reduced form with a bound sulfate ion in its active site is solved at 1.6-A resolution. Significant structural similarity is seen between arsenate reductase and bovine low molecular weight protein tyrosine phosphatase, despite very low sequence identity. The similarity is especially high between their active sites. It is further confirmed that this structural homology is relevant functionally by showing the phosphatase activity of the arsenate reductase in vitro. Thus, we can understand the arsenate reduction in the light of low molecular weight protein tyrosine phosphatase mechanism and also explain the catalytic roles of essential residues such as Cys-10, Cys-82, Cys-89, Arg-16, and Asp-105. A "triple cysteine redox relay" is proposed for the arsenate reduction mechanism.
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Affiliation(s)
- M S Bennett
- Department of Molecular Biophysics, Kemicentrum, P.O. Box 124, Lund University, SE-221 00 Lund, Sweden
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Mukhopadhyay R, Rosen BP. The phosphatase C(X)5R motif is required for catalytic activity of the Saccharomyces cerevisiae Acr2p arsenate reductase. J Biol Chem 2001; 276:34738-42. [PMID: 11461905 DOI: 10.1074/jbc.m103354200] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Acr2p detoxifies arsenate by reduction to arsenite in Saccharomyces cerevisiae. This reductase has been shown to require glutathione and glutaredoxin, suggesting that thiol chemistry might be involved in the reaction mechanism. Acr2p has a HC(X)(5)R motif, the signature sequence of the phosphate binding loop of the dual-specific and protein-tyrosine phosphatase family. In Acr2p these are residues His-75, Cys-76, and Arg-82, respectively. Acr2p has another sequence, (118)HCR, that is absent in phosphatases. Acr2p also has a third cysteine residue at position 106. Each of these cysteine residues was changed individually to serine residues, whereas the histidine and arginine residues were altered to alanines. Cells of Escherichia coli heterologously expressing the majority of the mutant ACR2 genes retained wild type resistance to arsenate, and the purified altered Acr2p proteins exhibited normal enzymatic properties. In contrast, cells expressing either the C76S or R82A mutations lost resistance to arsenate, and the purified proteins were inactive. These results suggest that Acr2p utilizes a phosphatase-like Cys(X)(5)Arg motif as the catalytic center to reduce arsenate to arsenite.
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Affiliation(s)
- R Mukhopadhyay
- Department of Biochemistry and Molecular Biology, Wayne State University, School of Medicine, Detroit, Michigan 48201, USA
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