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Fisher K, Halliwell T, Payne KAP, Ragala G, Hay S, Rigby SEJ, Leys D. Efficient NADPH-dependent dehalogenation afforded by a self-sufficient reductive dehalogenase. J Biol Chem 2023; 299:105086. [PMID: 37495113 PMCID: PMC10463259 DOI: 10.1016/j.jbc.2023.105086] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2023] [Revised: 07/10/2023] [Accepted: 07/19/2023] [Indexed: 07/28/2023] Open
Abstract
Reductive dehalogenases are corrinoid and iron-sulfur cluster-containing enzymes that catalyze the reductive removal of a halogen atom. The oxygen-sensitive and membrane-associated nature of the respiratory reductive dehalogenases has hindered their detailed kinetic study. In contrast, the evolutionarily related catabolic reductive dehalogenases are oxygen tolerant, with those that are naturally fused to a reductase domain with similarity to phthalate dioxygenase presenting attractive targets for further study. We present efficient heterologous expression of a self-sufficient catabolic reductive dehalogenase from Jhaorihella thermophila in Escherichia coli. Combining the use of maltose-binding protein as a solubility-enhancing tag with the btuCEDFB cobalamin uptake system affords up to 40% cobalamin occupancy and a full complement of iron-sulfur clusters. The enzyme is able to efficiently perform NADPH-dependent dehalogenation of brominated and iodinated phenolic compounds, including the flame retardant tetrabromobisphenol, under both anaerobic and aerobic conditions. NADPH consumption is tightly coupled to product formation. Surprisingly, corresponding chlorinated compounds only act as competitive inhibitors. Electron paramagnetic resonance spectroscopy reveals loss of the Co(II) signal observed in the resting state of the enzyme under steady-state conditions, suggesting accumulation of Co(I)/(III) species prior to the rate-limiting step. In vivo reductive debromination activity is readily observed, and when the enzyme is expressed in E. coli strain W, supports growth on 3-bromo-4-hydroxyphenylacetic as a sole carbon source. This demonstrates the potential for catabolic reductive dehalogenases for future application in bioremediation.
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Affiliation(s)
- Karl Fisher
- Manchester Institute of Biotechnology, University of Manchester, Manchester, UK
| | - Tom Halliwell
- Manchester Institute of Biotechnology, University of Manchester, Manchester, UK
| | - Karl A P Payne
- Manchester Institute of Biotechnology, University of Manchester, Manchester, UK
| | - Gabriel Ragala
- Manchester Institute of Biotechnology, University of Manchester, Manchester, UK
| | - Sam Hay
- Manchester Institute of Biotechnology, University of Manchester, Manchester, UK
| | - Stephen E J Rigby
- Manchester Institute of Biotechnology, University of Manchester, Manchester, UK
| | - David Leys
- Manchester Institute of Biotechnology, University of Manchester, Manchester, UK.
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2
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Zhang X, Wang Z, Li Z, Shaik S, Wang B. [4Fe–4S]-Mediated Proton-Coupled Electron Transfer Enables the Efficient Degradation of Chloroalkenes by Reductive Dehalogenases. ACS Catal 2023. [DOI: 10.1021/acscatal.2c06306] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Affiliation(s)
- Xuan Zhang
- State Key Laboratory Physical Chemistry of Solid Surfaces and Fujian Provincial Key Laboratory of Theoretical and Computational Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, P. R. China
| | - Zikuan Wang
- Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz 1, Mülheim an der Ruhr 45470, Germany
| | - Zhen Li
- State Key Laboratory Physical Chemistry of Solid Surfaces and Fujian Provincial Key Laboratory of Theoretical and Computational Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, P. R. China
| | - Sason Shaik
- Institute of Chemistry, The Hebrew University of Jerusalem, Jerusalem 91904, Israel
| | - Binju Wang
- State Key Laboratory Physical Chemistry of Solid Surfaces and Fujian Provincial Key Laboratory of Theoretical and Computational Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, P. R. China
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3
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Heterologous expression of active Dehalobacter spp. respiratory reductive dehalogenases in Escherichia coli. Appl Environ Microbiol 2021; 88:e0199321. [PMID: 34851719 DOI: 10.1128/aem.01993-21] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Reductive dehalogenases (RDases) are a family of redox enzymes that are required for anaerobic organohalide respiration, a microbial process that is useful in bioremediation. Structural and mechanistic studies of these enzymes have been greatly impeded due to challenges in RDase heterologous expression, potentially because of their cobamide-dependence. There have been a few successful attempts at RDase production in unconventional heterologous hosts, but a robust method has yet to be developed. Here we outline a novel respiratory RDase expression system using Escherichia coli. The overexpression of E. coli's cobamide transport system, btu, and anaerobic expression conditions were found to be essential for production of active RDases from Dehalobacter - an obligate organohalide respiring bacterium. The expression system was validated on six enzymes with amino acid sequence identities as low as 28%. Dehalogenation activity was verified for each RDase by assaying cell-free extracts of small-scale expression cultures on various chlorinated substrates including chloroalkanes, chloroethenes, and hexachlorocyclohexanes. Two RDases, TmrA from Dehalobacter sp. UNSWDHB and HchA from Dehalobacter sp. HCH1, were purified by nickel affinity chromatography. Incorporation of the cobamide and iron-sulfur cluster cofactors was verified; though, the precise cobalamin incorporation could not be determined due to variance between methodologies, and the specific activity of TmrA was consistent with that of the native enzyme. The heterologous expression of respiratory RDases, particularly from obligate organohalide respiring bacteria, has been extremely challenging and unreliable. Here we present a relatively straightforward E. coli expression system that has performed well for a variety of Dehalobacter spp. RDases. IMPORTANCE Understanding microbial reductive dehalogenation is important to refine the global halogen cycle and to improve bioremediation of halogenated contaminants; however, studies of the family of enzymes responsible are limited. Characterization of reductive dehalogenase enzymes has largely eluded researchers due to the lack of a reliable and high-yielding production method. We are presenting an approach to express reductive dehalogenase enzymes from Dehalobacter, a key group of organisms used in bioremediation, in E. coli. This expression system will propel the study of reductive dehalogenases by facilitating their production and isolation, allowing researchers to pursue more in-depth questions about the activity and structure of these enzymes. This platform will also provide a starting point to improve the expression of reductive dehalogenases from many other organisms.
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4
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Halliwell T, Fisher K, Payne KAP, Rigby SEJ, Leys D. Heterologous expression of cobalamin dependent class-III enzymes. Protein Expr Purif 2021; 177:105743. [PMID: 32871253 PMCID: PMC7585037 DOI: 10.1016/j.pep.2020.105743] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2020] [Revised: 08/25/2020] [Accepted: 08/26/2020] [Indexed: 11/29/2022]
Abstract
The family of cobalamin class-III dependent enzymes is composed of the reductive dehalogenases (RDases) and related epoxyqueuosine reductases. RDases are crucial for the energy conserving process of organohalide respiration. These enzymes have the ability to reductively cleave carbon-halogen bonds, present in a number of environmentally hazardous pollutants, making them of significant interest for bioremediation applications. Unfortunately, it is difficult to obtain sufficient yields of pure RDase isolated from organohalide respiring bacteria for biochemical studies. Hence, robust heterologous expression systems are required that yield the active holo-enzyme which requires both iron-sulphur cluster and cobalamin incorporation. We present a comparative study of the heterologous expression strains Bacillus megaterium, Escherichia coli HMS174(DE3), Shimwellia blattae and a commercial strain of Vibrio natrigenes, for cobalamin class-III dependent enzymes expression. The Nitratireductor pacificus pht-3B reductive dehalogenase (NpRdhA) and the epoxyqueuosine reductase from Streptococcus thermophilus (StoQ) were used as model enzymes. We also analysed whether co-expression of the cobalamin transporter BtuB, supports increased cobalamin incorporation into these enzymes in E. coli. We conclude that while expression in Bacillus megaterium resulted in the highest levels of cofactor incorporation, co-expression of BtuB in E. coli presents an appropriate balance between cofactor incorporation and protein yield in both cases.
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Affiliation(s)
- Tom Halliwell
- Manchester Institute of Biotechnology, University of Manchester, 131 Princess Street, Manchester, M1 7DN, UK
| | - Karl Fisher
- Manchester Institute of Biotechnology, University of Manchester, 131 Princess Street, Manchester, M1 7DN, UK
| | - Karl A P Payne
- Manchester Institute of Biotechnology, University of Manchester, 131 Princess Street, Manchester, M1 7DN, UK; Future Biomanufacturing Research Hub (FutureBRH), Manchester Institute of Biotechnology, University of Manchester, 131 Princess Street, Manchester, M1 7DN, UK
| | - Stephen E J Rigby
- Manchester Institute of Biotechnology, University of Manchester, 131 Princess Street, Manchester, M1 7DN, UK
| | - David Leys
- Manchester Institute of Biotechnology, University of Manchester, 131 Princess Street, Manchester, M1 7DN, UK.
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5
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Schubert T, von Reuß SH, Kunze C, Paetz C, Kruse S, Brand‐Schön P, Nelly AM, Nüske J, Diekert G. Guided cobamide biosynthesis for heterologous production of reductive dehalogenases. Microb Biotechnol 2019; 12:346-359. [PMID: 30549216 PMCID: PMC6389850 DOI: 10.1111/1751-7915.13339] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2018] [Revised: 10/23/2018] [Accepted: 10/30/2018] [Indexed: 12/01/2022] Open
Abstract
Cobamides (Cbas) are essential cofactors of reductive dehalogenases (RDases) in organohalide-respiring bacteria (OHRB). Changes in the Cba structure can influence RDase function. Here, we report on the cofactor versatility or selectivity of Desulfitobacterium RDases produced either in the native organism or heterologously. The susceptibility of Desulfitobacterium hafniense strain DCB-2 to guided Cba biosynthesis (i.e. incorporation of exogenous Cba lower ligand base precursors) was analysed. Exogenous benzimidazoles, azabenzimidazoles and 4,5-dimethylimidazole were incorporated by the organism into Cbas. When the type of Cba changed, no effect on the turnover rate of the 3-chloro-4-hydroxy-phenylacetate-converting enzyme RdhA6 and the 3,5-dichlorophenol-dehalogenating enzyme RdhA3 was observed. The impact of the amendment of Cba lower ligand precursors on RDase function was also investigated in Shimwellia blattae, the Cba producer used for the heterologous production of Desulfitobacterium RDases. The recombinant tetrachloroethene RDase (PceAY51 ) appeared to be non-selective towards different Cbas. However, the functional production of the 1,2-dichloroethane-dihaloeliminating enzyme (DcaA) of Desulfitobacterium dichloroeliminans was completely prevented in cells producing 5,6-dimethylbenzimidazolyl-Cba, but substantially enhanced in cells that incorporated 5-methoxybenzimidazole into the Cba cofactor. The results of the study indicate the utilization of a range of different Cbas by Desulfitobacterium RDases with selected representatives apparently preferring distinct Cbas.
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Affiliation(s)
- Torsten Schubert
- Department of Applied and Ecological MicrobiologyInstitute of MicrobiologyFriedrich Schiller UniversityPhilosophenweg 12D‐07743JenaGermany
| | - Stephan H. von Reuß
- Department of Bioorganic ChemistryMax Planck Institute for Chemical EcologyHans‐Knöll‐Straße 8D‐07745JenaGermany
- Present address:
Laboratory for Bioanalytical ChemistryInstitute of ChemistryUniversity of NeuchâtelAvenue de Bellevaux 512000NeuchâtelSwitzerland
| | - Cindy Kunze
- Department of Applied and Ecological MicrobiologyInstitute of MicrobiologyFriedrich Schiller UniversityPhilosophenweg 12D‐07743JenaGermany
- Present address:
DECHEMA‐ForschungsinstitutTheodor‐Heuss‐Allee 25D‐60486Frankfurt am MainGermany
| | - Christian Paetz
- Research Group Biosynthesis/NMRMax Planck Institute for Chemical EcologyHans‐Knöll‐Straße 8D‐07745JenaGermany
| | - Stefan Kruse
- Department of Applied and Ecological MicrobiologyInstitute of MicrobiologyFriedrich Schiller UniversityPhilosophenweg 12D‐07743JenaGermany
| | - Peggy Brand‐Schön
- Department of Applied and Ecological MicrobiologyInstitute of MicrobiologyFriedrich Schiller UniversityPhilosophenweg 12D‐07743JenaGermany
| | - Anita Mac Nelly
- Department of Applied and Ecological MicrobiologyInstitute of MicrobiologyFriedrich Schiller UniversityPhilosophenweg 12D‐07743JenaGermany
| | - Jörg Nüske
- Department of Applied and Ecological MicrobiologyInstitute of MicrobiologyFriedrich Schiller UniversityPhilosophenweg 12D‐07743JenaGermany
| | - Gabriele Diekert
- Department of Applied and Ecological MicrobiologyInstitute of MicrobiologyFriedrich Schiller UniversityPhilosophenweg 12D‐07743JenaGermany
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6
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Gagnon DM, Stich TA, Mehta AP, Abdelwahed SH, Begley TP, Britt RD. An Aminoimidazole Radical Intermediate in the Anaerobic Biosynthesis of the 5,6-Dimethylbenzimidazole Ligand to Vitamin B12. J Am Chem Soc 2018; 140:12798-12807. [PMID: 30208703 DOI: 10.1021/jacs.8b05686] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Organisms that perform the de novo biosynthesis of cobalamin (vitamin B12) do so via unique pathways depending on the presence of oxygen in the environment. The anaerobic biosynthesis pathway of 5,6-dimethylbenzimidazole, the so-called "lower ligand" to the cobalt center, has been recently identified. This process begins with the conversion of 5-aminoimidazole ribotide (AIR) to 5-hydroxybenzimidazole (HBI) by the radical S-adenosyl-l-methionine (SAM) enzyme BzaF, also known as HBI synthase. In this work we report the characterization of a radical intermediate in the reaction of BzaF using electron paramagnetic resonance spectroscopy. Using various isotopologues of AIR, we extracted hyperfine parameters for a number of nuclei, allowing us to propose plausible chemical compositions and structures for this intermediate. Specifically, we find that an aminoimidazole radical is formed in close proximity to a fragment of the ribose ring. These findings induce the revision of past proposed mechanisms and illustrate the ability of radical SAM enzymes to tightly control the radical chemistry that they engender.
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Affiliation(s)
- Derek M Gagnon
- Department of Chemistry , University of California , Davis , California 95616 , United States
| | - Troy A Stich
- Department of Chemistry , University of California , Davis , California 95616 , United States
| | - Angad P Mehta
- Department of Chemistry , Texas A&M University , College Station , Texas 77843 , United States
| | - Sameh H Abdelwahed
- Department of Chemistry , Texas A&M University , College Station , Texas 77843 , United States
| | - Tadhg P Begley
- Department of Chemistry , Texas A&M University , College Station , Texas 77843 , United States
| | - R David Britt
- Department of Chemistry , University of California , Davis , California 95616 , United States
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7
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Nakamura R, Obata T, Nojima R, Hashimoto Y, Noguchi K, Ogawa T, Yohda M. Functional Expression and Characterization of Tetrachloroethene Dehalogenase From Geobacter sp. Front Microbiol 2018; 9:1774. [PMID: 30147676 PMCID: PMC6095959 DOI: 10.3389/fmicb.2018.01774] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2017] [Accepted: 07/16/2018] [Indexed: 11/13/2022] Open
Abstract
Reductive dehalogenase (RDase) consists of two parts, RdhA and RdhB. RdhA is the catalytic subunit, harboring a cobalamin cofactor and two Fe-S clusters. RdhA is anchored to the cytoplasmic membrane via the membrane anchoring subunit, RdhB. There are many genes encoding RDases in the genome of organohalide-respiring bacteria, including Dehalococcoides spp. However, most genes have not been functionally characterized. Biochemical studies on RDases have been hampered by difficulties encountered in their expression and purification. In this study, we have expressed, purified and characterized RdhA of RDase for tetrachloroethene (PceA) from Geobacter sp. PceA was expressed as a fusion protein with a trigger factor tag in Escherichia coli. PceA was purified and denatured in aerobic condition. Subsequently, this protein was refolded in the presence of FeCl3, Na2S and cobalamin in anaerobic condition. The reconstituted PceA exhibited dechlorination ability for tetrachloroethene. UV-Vis spectroscopy has shown that it contains cobalamin and Fe-S clusters. Since this method requires anaerobic manipulation only in the reconstituting process and has a relatively high yield, it will enable further biochemical studies of RDases.
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Affiliation(s)
- Ryuki Nakamura
- Department of Biotechnology and Life Science, Tokyo University of Agriculture and Technology, Tokyo, Japan
| | - Tomohiro Obata
- Department of Biotechnology and Life Science, Tokyo University of Agriculture and Technology, Tokyo, Japan
| | - Ryota Nojima
- Department of Biotechnology and Life Science, Tokyo University of Agriculture and Technology, Tokyo, Japan
| | - Yohey Hashimoto
- Department of Bioapplications and Systems Engineering, Tokyo University of Agriculture and Technology, Tokyo, Japan
| | - Keiichi Noguchi
- Instrumentation Analysis Center, Tokyo University of Agriculture and Technology, Tokyo, Japan
| | - Takahiro Ogawa
- Institute of Global Innovation Research, Tokyo University of Agriculture and Technology, Tokyo, Japan
| | - Masafumi Yohda
- Department of Biotechnology and Life Science, Tokyo University of Agriculture and Technology, Tokyo, Japan.,Institute of Global Innovation Research, Tokyo University of Agriculture and Technology, Tokyo, Japan
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8
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Collins FA, Fisher K, Payne KAP, Gaytan Mondragon S, Rigby SEJ, Leys D. NADPH-Driven Organohalide Reduction by a Nonrespiratory Reductive Dehalogenase. Biochemistry 2018; 57:3493-3502. [PMID: 29630828 DOI: 10.1021/acs.biochem.8b00255] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Reductive dehalogenases are corrinoid and iron-sulfur cluster-dependent enzymes that mostly act as the terminal oxidoreductases in the bacterial organohalide respiration process. This process often leads to detoxification of recalcitrant organohalide pollutants. While low cell yields and oxygen sensitivity hamper the study of many reductive dehalogenases, this is not the case for the nonrespiratory reductive dehalogenase NpRdhA from Nitratireductor pacificus. We here report in vitro and in vivo reconstitution of an NADPH-dependent reducing system for NpRdhA. Surprisingly, NpRdhA mediated organohalide reduction could not be supported using N. pacificus ferredoxin-NAD(P)H oxidoreductase and associated ferredoxins. Instead, we found a nonphysiological system comprised of the Escherichia coli flavodoxin reductase (EcFldr) in combination with spinach ferredoxin (SpFd) was able to support NADPH-dependent organohalide reduction by NpRdhA. Using this system, organohalide reduction can be performed under both anaerobic and aerobic conditions, with 1.1 ± 0.1 and 3.5 ± 0.3 equiv of NADPH consumed per product produced, respectively. No significant enzyme inactivation under aerobic conditions was observed, suggesting a Co(I) species is unlikely to be present under steady state conditions. Furthermore, reduction of the Co(II) resting state was not observed in the absence of substrate. Only the coexpression of EcFldr, SpFd, and NpRdhA in Bacillus megaterium conferred the latter with the ability to reduce brominated NpRdhA substrates in vivo, in agreement with our in vitro observations. Our work provides new insights into biological reductive dehalogenase reduction and establishes a blueprint for the minimal functional organohalide reduction module required for bioremediation in situ.
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Affiliation(s)
- Fraser A Collins
- Manchester Institute of Biotechnology , University of Manchester , 131 Princess Street , Manchester M1 7DN , U.K
| | - Karl Fisher
- Manchester Institute of Biotechnology , University of Manchester , 131 Princess Street , Manchester M1 7DN , U.K
| | - Karl A P Payne
- Manchester Institute of Biotechnology , University of Manchester , 131 Princess Street , Manchester M1 7DN , U.K
| | - Samantha Gaytan Mondragon
- Manchester Institute of Biotechnology , University of Manchester , 131 Princess Street , Manchester M1 7DN , U.K
| | - Stephen E J Rigby
- Manchester Institute of Biotechnology , University of Manchester , 131 Princess Street , Manchester M1 7DN , U.K
| | - David Leys
- Manchester Institute of Biotechnology , University of Manchester , 131 Princess Street , Manchester M1 7DN , U.K
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9
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Suzuki Y, Nakamura M, Otsuka Y, Suzuki N, Ohyama K, Kawakami T, Sato-Izawa K, Navarro RR, Hishiyama S, Inoue K, Kameyama T, Takahashi A, Katayama Y. Cloning and sequencing of the gene encoding the enzyme for the reductive cleavage of diaryl ether bonds of 2,3,7,8-tetrachlorodibenzo-p-dioxin in Geobacillus thermodenitrificans UZO 3. J Biosci Bioeng 2018; 126:488-496. [PMID: 29805114 DOI: 10.1016/j.jbiosc.2018.04.013] [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] [Received: 11/20/2017] [Revised: 03/20/2018] [Accepted: 04/20/2018] [Indexed: 11/17/2022]
Abstract
We have previously reported that a cell-free extract prepared from Geobacillus thermodenitrificans UZO 3 reductively cleaves diaryl ether bonds of 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD), a dioxin with the highest toxicity, in a sequential fashion producing 3',4',4,5-tetrachloro-2-hydroxydiphenyl ether (TCDE) as the intermediate, and 3,4-dichlorophenol (DCP) as the final reaction product. The detection of TCDE implicated the discovery of an unprecedented dioxin-degrading enzyme that reductively cleaves the diaryl ether bonds. In this study, we report the cloning and sequencing of the dioxin reductive etherase gene dreE which codes for the 2,3,7,8-TCDD-degrading enzyme. We showed that dreE was expressed in Escherichia coli and that the product of the expression could reductively cleave diaryl ether bonds of 2,3,7,8-TCDD to produce TCDE. Furthermore, we established that the amino acid sequence encoded by dreE was homologous to an enzyme with yet unknown function that is encoded by a gene located in the riboflavin (vitamin B2) biosynthesis operon in Bacillus subtilis. We also showed that the amino acid sequence possesses a coenzyme A (CoA) binding site that is conserved in the N-acyltransferase superfamily. For the first time, the degradation of 2,3,7,8-TCDD at the molecular level using a enzyme of bacterial origin has been demonstrated. A novel mechanism model for the reductive cleavage of diaryl ether bond of 2,3,7,8-TCDD was also proposed.
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Affiliation(s)
- Yuzo Suzuki
- Takasago Thermal Engineering Co. Ltd., Shinjyuku, Tokyo 160-0022, Japan
| | - Masaya Nakamura
- Forestry and Forest Products Research Institute, 1 Matsunosato, Tsukuba, Ibaraki 305-8687, Japan.
| | - Yuichiro Otsuka
- Forestry and Forest Products Research Institute, 1 Matsunosato, Tsukuba, Ibaraki 305-8687, Japan
| | - Nao Suzuki
- Graduate School of Bio-Applications and Systems Engineering, Tokyo University of Agriculture and Technology, Koganei, Tokyo 184-8588, Japan
| | - Keisuke Ohyama
- Graduate School of Bio-Applications and Systems Engineering, Tokyo University of Agriculture and Technology, Koganei, Tokyo 184-8588, Japan
| | - Takeshi Kawakami
- Takasago Thermal Engineering Co. Ltd., Shinjyuku, Tokyo 160-0022, Japan
| | - Kanna Sato-Izawa
- Department of Bioscience, Faculty of Life Sciences, Tokyo University of Agriculture, Setagaya, Tokyo 156-8502, Japan
| | - Ronald R Navarro
- Forestry and Forest Products Research Institute, 1 Matsunosato, Tsukuba, Ibaraki 305-8687, Japan
| | - Shojiro Hishiyama
- Forestry and Forest Products Research Institute, 1 Matsunosato, Tsukuba, Ibaraki 305-8687, Japan
| | - Kouya Inoue
- Kantteku Co. Ltd., Bunkyo, Tokyo 112-0004, Japan
| | | | - Atsushi Takahashi
- Takasago Thermal Engineering Co. Ltd., Shinjyuku, Tokyo 160-0022, Japan
| | - Yoshihiro Katayama
- College of Bioresource Sciences, Nihon University, Fujisawa, Kanagawa 252-0880, Japan
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10
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Jugder BE, Payne KAP, Fisher K, Bohl S, Lebhar H, Manefield M, Lee M, Leys D, Marquis CP. Heterologous Production and Purification of a Functional Chloroform Reductive Dehalogenase. ACS Chem Biol 2018; 13:548-552. [PMID: 29363941 DOI: 10.1021/acschembio.7b00846] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Reductive dehalogenases (RDases) are key enzymes involved in the respiratory process of anaerobic organohalide respiring bacteria (ORB). Heterologous expression of respiratory RDases is desirable for structural and functional studies; however, there are few reports of successful expression of these enzymes. Dehalobacter sp. strain UNSWDHB is an ORB, whose preferred electron acceptor is chloroform. This study describes efforts to express recombinant reductive dehalogenase (TmrA), derived from UNSW DHB, using the heterologous hosts Escherichia coli and Bacillus megaterium. Here, we report the recombinant expression of soluble and functional TmrA, using B. megaterium as an expression host under a xylose-inducible promoter. Successful incorporation of iron-sulfur clusters and a corrinoid cofactor was demonstrated using UV-vis spectroscopic analyses. In vitro dehalogenation of chloroform using purified recombinant TmrA was demonstrated. This is the first known report of heterologous expression and purification of a respiratory reductive dehalogenase from an obligate organohalide respiring bacterium.
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Affiliation(s)
- Bat-Erdene Jugder
- School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, New South Wales 2052, Australia
- Manchester Institute of Biotechnology, University of Manchester, Manchester M1 7 DN, United Kingdom
| | - Karl A. P. Payne
- Manchester Institute of Biotechnology, University of Manchester, Manchester M1 7 DN, United Kingdom
| | - Karl Fisher
- Manchester Institute of Biotechnology, University of Manchester, Manchester M1 7 DN, United Kingdom
| | - Susanne Bohl
- School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, New South Wales 2052, Australia
- Department of Biotechnology, Mannheim University of Applied Sciences, Mannheim, Germany
| | - Helene Lebhar
- School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, New South Wales 2052, Australia
| | - Mike Manefield
- School of Civil and Environmental Engineering, University of New South Wales, Sydney, New South Wales 2052, Australia
- School of Chemical Engineering, University of New South Wales, Sydney, New South Wales 2052, Australia
| | - Matthew Lee
- School of Civil and Environmental Engineering, University of New South Wales, Sydney, New South Wales 2052, Australia
| | - David Leys
- Manchester Institute of Biotechnology, University of Manchester, Manchester M1 7 DN, United Kingdom
| | - Christopher P. Marquis
- School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, New South Wales 2052, Australia
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11
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Puentes Jácome LA, Edwards EA. A switch of chlorinated substrate causes emergence of a previously undetected native Dehalobacter population in an established Dehalococcoides-dominated chloroethene-dechlorinating enrichment culture. FEMS Microbiol Ecol 2018; 93:4569067. [PMID: 29088371 DOI: 10.1093/femsec/fix141] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2017] [Accepted: 10/26/2017] [Indexed: 01/08/2023] Open
Abstract
Chlorobenzenes are soil and groundwater pollutants of concern that can be reductively dehalogenated by organohalide-respiring bacteria from the genera Dehalococcoides and Dehalobacter. The bioaugmentation culture KB-1® harbours Dehalococcoides mccartyi spp. that reductively dehalogenate trichloroethene to ethene. It contains more than 30 reductive dehalogenase genes; some of them are highly similar to genes found in the chlorobenzene-respiring Dehalococcoides mccartyi strain CBDB1. We explored the chlorobenzene dehalogenation capability of the KB-1 enrichment culture using 1,2,4-trichlorobenzene (1,2,4-TCB). We achieved adaptation of KB-1 to 1,2,4-TCB that is dehalogenated to a mixture of dichlorobenzenes, and subsequently to monochlorobenzene and benzene. Surprisingly, a native Dehalobacter population, and not a Dehalococcoides population, couples the dechlorination of 1,2,4-TCB to growth achieving an average yield of 1.1 ± 0.6 × 1013 cells per mole of Cl- released. Interestingly, the dechlorination of 1,2,4-TCB occurs alongside the complete dechlorination of trichloroethene to ethene in cultures fed both electron acceptors. Dehalobacter was not previously identified as a major player in KB-1, but its ecological niche was favoured by the introduction of 1,2,4-TCB. Based on 16S rRNA phylogeny, Dehalobacter populations seem to cluster into specialised clades, and are likely undergoing substrate specialisation as a strategy to reduce competition for electron acceptors.
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Affiliation(s)
- Luz A Puentes Jácome
- Department of Chemical Engineering and Applied Chemistry, University of Toronto, Toronto, ON M5S 3E5, Canada
| | - Elizabeth A Edwards
- Department of Chemical Engineering and Applied Chemistry, University of Toronto, Toronto, ON M5S 3E5, Canada.,Department of Cell and Systems Biology, University of Toronto, Toronto, ON M5S 1A1, Canada
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Liao RZ, Chen SL, Siegbahn PEM. Unraveling the Mechanism and Regioselectivity of the B12-Dependent Reductive Dehalogenase PceA. Chemistry 2016; 22:12391-9. [DOI: 10.1002/chem.201601575] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2016] [Indexed: 01/09/2023]
Affiliation(s)
- Rong-Zhen Liao
- Key Laboratory of Material Chemistry for Energy Conversion and Storage; Ministry of Education; Hubei Key Laboratory of Bioinorganic Chemistry and Materia Medica; Hubei Key Laboratory of Materials Chemistry and Service Failure; School of Chemistry and Chemical Engineering; Huazhong University of Science and Technology; Wuhan 430074 P. R. China
| | - Shi-Lu Chen
- School of Chemistry; Beijing Institute of Technology; Beijing 100081 P. R. China
| | - Per E. M. Siegbahn
- Department of Organic Chemistry; Arrhenius Laboratory; Stockholm University; 10691 Stockholm Sweden
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13
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Jugder BE, Ertan H, Bohl S, Lee M, Marquis CP, Manefield M. Organohalide Respiring Bacteria and Reductive Dehalogenases: Key Tools in Organohalide Bioremediation. Front Microbiol 2016; 7:249. [PMID: 26973626 PMCID: PMC4771760 DOI: 10.3389/fmicb.2016.00249] [Citation(s) in RCA: 99] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2015] [Accepted: 02/15/2016] [Indexed: 01/31/2023] Open
Abstract
Organohalides are recalcitrant pollutants that have been responsible for substantial contamination of soils and groundwater. Organohalide-respiring bacteria (ORB) provide a potential solution to remediate contaminated sites, through their ability to use organohalides as terminal electron acceptors to yield energy for growth (i.e., organohalide respiration). Ideally, this process results in non- or lesser-halogenated compounds that are mostly less toxic to the environment or more easily degraded. At the heart of these processes are reductive dehalogenases (RDases), which are membrane bound enzymes coupled with other components that facilitate dehalogenation of organohalides to generate cellular energy. This review focuses on RDases, concentrating on those which have been purified (partially or wholly) and functionally characterized. Further, the paper reviews the major bacteria involved in organohalide breakdown and the evidence for microbial evolution of RDases. Finally, the capacity for using ORB in a bioremediation and bioaugmentation capacity are discussed.
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Affiliation(s)
- Bat-Erdene Jugder
- School of Biotechnology and Biomolecular Sciences, University of New South Wales Sydney, NSW, Australia
| | - Haluk Ertan
- School of Biotechnology and Biomolecular Sciences, University of New South WalesSydney, NSW, Australia; Department of Molecular Biology and Genetics, Istanbul UniversityIstanbul, Turkey
| | - Susanne Bohl
- School of Biotechnology and Biomolecular Sciences, University of New South WalesSydney, NSW, Australia; Department of Biotechnology, Mannheim University of Applied SciencesMannheim, Germany
| | - Matthew Lee
- School of Biotechnology and Biomolecular Sciences, University of New South Wales Sydney, NSW, Australia
| | - Christopher P Marquis
- School of Biotechnology and Biomolecular Sciences, University of New South Wales Sydney, NSW, Australia
| | - Michael Manefield
- School of Biotechnology and Biomolecular Sciences, University of New South Wales Sydney, NSW, Australia
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Jugder BE, Ertan H, Lee M, Manefield M, Marquis CP. Reductive Dehalogenases Come of Age in Biological Destruction of Organohalides. Trends Biotechnol 2015; 33:595-610. [DOI: 10.1016/j.tibtech.2015.07.004] [Citation(s) in RCA: 70] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2015] [Revised: 07/27/2015] [Accepted: 07/30/2015] [Indexed: 11/28/2022]
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15
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Payne KAP, Fisher K, Sjuts H, Dunstan MS, Bellina B, Johannissen L, Barran P, Hay S, Rigby SEJ, Leys D. Epoxyqueuosine Reductase Structure Suggests a Mechanism for Cobalamin-dependent tRNA Modification. J Biol Chem 2015; 290:27572-81. [PMID: 26378237 PMCID: PMC4646009 DOI: 10.1074/jbc.m115.685693] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2015] [Indexed: 01/11/2023] Open
Abstract
Queuosine (Q) is a hypermodified RNA base that replaces guanine in the wobble positions of 5′-GUN-3′ tRNA molecules. Q is exclusively made by bacteria, and the corresponding queuine base is a micronutrient salvaged by eukaryotic species. The final step in Q biosynthesis is the reduction of the epoxide precursor, epoxyqueuosine, to yield the Q cyclopentene ring. The epoxyqueuosine reductase responsible, QueG, shares distant homology with the cobalamin-dependent reductive dehalogenase (RdhA), however the role played by cobalamin in QueG catalysis has remained elusive. We report the solution and structural characterization of Streptococcus thermophilus QueG, revealing the enzyme harbors a redox chain consisting of two [4Fe-4S] clusters and a cob(II)alamin in the base-off form, similar to RdhAs. In contrast to the shared redox chain architecture, the QueG active site shares little homology with RdhA, with the notable exception of a conserved Tyr that is proposed to function as a proton donor during reductive dehalogenation. Docking of an epoxyqueuosine substrate suggests the QueG active site places the substrate cyclopentane moiety in close proximity of the cobalt. Both the Tyr and a conserved Asp are implicated as proton donors to the epoxide leaving group. This suggests that, in contrast to the unusual carbon-halogen bond chemistry catalyzed by RdhAs, QueG acts via Co-C bond formation. Our study establishes the common features of Class III cobalamin-dependent enzymes, and reveals an unexpected diversity in the reductive chemistry catalyzed by these enzymes.
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Affiliation(s)
- Karl A P Payne
- From the Manchester Institute of Biotechnology, University of Manchester, Princess Street 131, Manchester M1 7DN, United Kingdom
| | - Karl Fisher
- From the Manchester Institute of Biotechnology, University of Manchester, Princess Street 131, Manchester M1 7DN, United Kingdom
| | - Hanno Sjuts
- From the Manchester Institute of Biotechnology, University of Manchester, Princess Street 131, Manchester M1 7DN, United Kingdom
| | - Mark S Dunstan
- From the Manchester Institute of Biotechnology, University of Manchester, Princess Street 131, Manchester M1 7DN, United Kingdom
| | - Bruno Bellina
- From the Manchester Institute of Biotechnology, University of Manchester, Princess Street 131, Manchester M1 7DN, United Kingdom
| | - Linus Johannissen
- From the Manchester Institute of Biotechnology, University of Manchester, Princess Street 131, Manchester M1 7DN, United Kingdom
| | - Perdita Barran
- From the Manchester Institute of Biotechnology, University of Manchester, Princess Street 131, Manchester M1 7DN, United Kingdom
| | - Sam Hay
- From the Manchester Institute of Biotechnology, University of Manchester, Princess Street 131, Manchester M1 7DN, United Kingdom
| | - Stephen E J Rigby
- From the Manchester Institute of Biotechnology, University of Manchester, Princess Street 131, Manchester M1 7DN, United Kingdom
| | - David Leys
- From the Manchester Institute of Biotechnology, University of Manchester, Princess Street 131, Manchester M1 7DN, United Kingdom
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16
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Parthasarathy A, Stich TA, Lohner ST, Lesnefsky A, Britt RD, Spormann AM. Biochemical and EPR-spectroscopic investigation into heterologously expressed vinyl chloride reductive dehalogenase (VcrA) from Dehalococcoides mccartyi strain VS. J Am Chem Soc 2015; 137:3525-32. [PMID: 25686300 PMCID: PMC4516053 DOI: 10.1021/ja511653d] [Citation(s) in RCA: 56] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Reductive dehalogenases play a critical role in the microbial detoxification of aquifers contaminated with chloroethenes and chlorethanes by catalyzing the reductive elimination of a halogen. We report here the first heterologous production of vinyl chloride reductase VcrA from Dehalococcoides mccartyi strain VS. Heterologously expressed VcrA was reconstituted to its active form by addition of hydroxocobalamin/adenosylcobalamin, Fe(3+), and sulfide in the presence of mercaptoethanol. The kinetic properties of reconstituted VcrA catalyzing vinyl chloride reduction with Ti(III)-citrate as reductant and methyl viologen as mediator were similar to those obtained previously for VcrA as isolated from D. mccartyi strain VS. VcrA was also found to catalyze a novel reaction, the environmentally important dihaloelimination of 1,2-dichloroethane to ethene. Electron paramagnetic resonance (EPR) spectroscopic studies with reconstituted VcrA in the presence of mercaptoethanol revealed the presence of Cob(II)alamin. Addition of Ti(III)-citrate resulted in the appearance of a new signal characteristic of a reduced [4Fe-4S] cluster and the disappearance of the Cob(II)alamin signal. UV-vis absorption spectroscopy of Ti(III)citrate-treated samples revealed the formation of two new absorption maxima characteristic of Cob(I)alamin. No evidence for the presence of a [3Fe-4S] cluster was found. We postulate that during the reaction cycle of VcrA, a reduced [4Fe-4S] cluster reduces Co(II) to Co(I) of the enzyme-bound cobalamin. Vinyl chloride reduction to ethene would be initiated when Cob(I)alamin transfers an electron to the substrate, generating a vinyl radical as a potential reaction intermediate.
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Affiliation(s)
- Anutthaman Parthasarathy
- Departments of Chemical Engineering and Civil and Environmental Engineering, Stanford University, Stanford, California 94305, United States
| | - Troy A. Stich
- Department of Chemistry, University of California, Davis, Davis, California 95616, United States
| | - Svenja T. Lohner
- Departments of Chemical Engineering and Civil and Environmental Engineering, Stanford University, Stanford, California 94305, United States
| | - Ann Lesnefsky
- Departments of Chemical Engineering and Civil and Environmental Engineering, Stanford University, Stanford, California 94305, United States
| | - R. David Britt
- Department of Chemistry, University of California, Davis, Davis, California 95616, United States
| | - Alfred M. Spormann
- Departments of Chemical Engineering and Civil and Environmental Engineering, Stanford University, Stanford, California 94305, United States
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17
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Functional heterologous production of reductive dehalogenases from Desulfitobacterium hafniense strains. Appl Environ Microbiol 2014; 80:4313-22. [PMID: 24814779 DOI: 10.1128/aem.00881-14] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
The anaerobic dehalogenation of organohalides is catalyzed by the reductive dehalogenase (RdhA) enzymes produced in phylogenetically diverse bacteria. These enzymes contain a cobamide cofactor at the active site and two iron-sulfur clusters. In this study, the tetrachloroethene (PCE) reductive dehalogenase (PceA) of the Gram-positive Desulfitobacterium hafniense strain Y51 was produced in a catalytically active form in the nondechlorinating, cobamide-producing bacterium Shimwellia blattae (ATCC 33430), a Gram-negative gammaproteobacterium. The formation of recombinant catalytically active PceA enzyme was significantly enhanced when its dedicated PceT chaperone was coproduced and when 5,6-dimethylbenzimidazole and hydroxocobalamin were added to the S. blattae cultures. The experiments were extended to D. hafniense DCB-2, a reductively dehalogenating bacterium harboring multiple rdhA genes. To elucidate the substrate spectrum of the rdhA3 gene product of this organism, the recombinant enzyme was tested for the conversion of different dichlorophenols (DCP) in crude extracts of an RdhA3-producing S. blattae strain. 3,5-DCP, 2,3-DCP, and 2,4-DCP, but not 2,6-DCP and 3,4-DCP, were reductively dechlorinated by the recombinant RdhA3. In addition, this enzyme dechlorinated PCE to trichloroethene at low rates.
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18
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Richardson RE. Genomic insights into organohalide respiration. Curr Opin Biotechnol 2013; 24:498-505. [DOI: 10.1016/j.copbio.2013.02.014] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2013] [Revised: 02/11/2013] [Accepted: 02/12/2013] [Indexed: 12/14/2022]
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Tang S, Edwards EA. Identification of Dehalobacter reductive dehalogenases that catalyse dechlorination of chloroform, 1,1,1-trichloroethane and 1,1-dichloroethane. Philos Trans R Soc Lond B Biol Sci 2013; 368:20120318. [PMID: 23479748 DOI: 10.1098/rstb.2012.0318] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Two novel reductive dehalogenases (RDases) that are highly similar to each other but catalyse distinct dechlorination reactions were identified from Dehalobacter-containing mixed cultures. These two RDases were partially purified from crude protein extracts of anaerobic dechlorinating enrichment cultures using blue native polyacrylamide gel electrophoresis. Gel slices were assayed for dechlorinating activity, and associated proteins were identified using liquid chromatography tandem mass spectrometry with the metagenome of the parent culture as the reference database. The two RDases identified, annotated as CfrA and DcrA, share an amino acid identity of 95.2 per cent, but use different substrates: CfrA dechlorinates chloroform (CF) and 1,1,1-trichloroethane (1,1,1-TCA), but not 1,1-dichloroethane; DcrA dechlorinates 1,1-dichloroethane, but not CF or 1,1,1-TCA. These two novel RDases share no more than 40 per cent amino acid identity to any other known or putative RDases, but both have a twin-arginine motif and two iron-sulfur binding motifs conserved in most RDases. Peptides specific to two putative membrane anchor proteins, annotated as CfrB and DcrB, were also detected in gel slices.
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Affiliation(s)
- Shuiquan Tang
- Department of Chemical Engineering and Applied Chemistry, University of Toronto, Toronto, Ontario, Canada
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20
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Leys D, Adrian L, Smidt H. Organohalide respiration: microbes breathing chlorinated molecules. Philos Trans R Soc Lond B Biol Sci 2013; 368:20120316. [PMID: 23479746 DOI: 10.1098/rstb.2012.0316] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Bacterial respiration has taken advantage of almost every redox couple present in the environment. The reduction of organohalide compounds to release the reduced halide ion drives energy production in organohalide respiring bacteria. This process is centred around the reductive dehalogenases, an iron-sulfur and corrinoid containing family of enzymes. These enzymes, transcriptional regulators and the bacteria themselves have potential to contribute to future bioremediation solutions that address the pollution of the environment by halogenated organic compounds.
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Affiliation(s)
- David Leys
- Manchester Institute of Biotechnology, University of Manchester, MIB 131 Princess Street, Manchester, UK.
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Hug LA, Maphosa F, Leys D, Löffler FE, Smidt H, Edwards EA, Adrian L. Overview of organohalide-respiring bacteria and a proposal for a classification system for reductive dehalogenases. Philos Trans R Soc Lond B Biol Sci 2013; 368:20120322. [PMID: 23479752 DOI: 10.1098/rstb.2012.0322] [Citation(s) in RCA: 194] [Impact Index Per Article: 17.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Organohalide respiration is an anaerobic bacterial respiratory process that uses halogenated hydrocarbons as terminal electron acceptors during electron transport-based energy conservation. This dechlorination process has triggered considerable interest for detoxification of anthropogenic groundwater contaminants. Organohalide-respiring bacteria have been identified from multiple bacterial phyla, and can be categorized as obligate and non-obligate organohalide respirers. The majority of the currently known organohalide-respiring bacteria carry multiple reductive dehalogenase genes. Analysis of a curated set of reductive dehalogenases reveals that sequence similarity and substrate specificity are generally not correlated, making functional prediction from sequence information difficult. In this article, an orthologue-based classification system for the reductive dehalogenases is proposed to aid integration of new sequencing data and to unify terminology.
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Affiliation(s)
- Laura A Hug
- Department of Cell and Systems Biology, University of Toronto, Toronto, ON, Canada
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