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Barroso GT, Garcia AA, Knapp M, Boggs DG, Bridwell-Rabb J. Purification and characterization of a Rieske oxygenase and its NADH-regenerating partner proteins. Methods Enzymol 2024; 703:215-242. [PMID: 39260997 DOI: 10.1016/bs.mie.2024.05.015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/13/2024]
Abstract
The Rieske non-heme iron oxygenases (Rieske oxygenases) comprise a class of metalloenzymes that are involved in the biosynthesis of complex natural products and the biodegradation of aromatic pollutants. Despite this desirable catalytic repertoire, industrial implementation of Rieske oxygenases has been hindered by the multicomponent nature of these enzymes and their requirement for expensive reducing equivalents in the form of a reduced nicotinamide adenine dinucleotide cosubstrate (NAD(P)H). Fortunately, however, some Rieske oxygenases co-occur with accessory proteins, that through a downstream reaction, recycle the needed NAD(P)H for catalysis. As these pathways and accessory proteins are attractive for bioremediation applications and enzyme engineering campaigns, herein, we describe methods for assembling Rieske oxygenase pathways in vitro. Further, using the TsaMBCD pathway as a model system, in this chapter, we provide enzymatic, spectroscopic, and crystallographic methods that can be adapted to explore both Rieske oxygenases and their co-occurring accessory proteins.
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Affiliation(s)
- Gage T Barroso
- Department of Chemistry, University of Michigan, Ann Arbor, MI, United States
| | | | - Madison Knapp
- Department of Chemistry, University of Michigan, Ann Arbor, MI, United States
| | - David G Boggs
- Department of Chemistry, University of Michigan, Ann Arbor, MI, United States
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2
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Tian J, Boggs DG, Donnan PH, Barroso GT, Garcia AA, Dowling DP, Buss JA, Bridwell-Rabb J. The NADH recycling enzymes TsaC and TsaD regenerate reducing equivalents for Rieske oxygenase chemistry. J Biol Chem 2023; 299:105222. [PMID: 37673337 PMCID: PMC10579966 DOI: 10.1016/j.jbc.2023.105222] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2023] [Revised: 08/22/2023] [Accepted: 08/31/2023] [Indexed: 09/08/2023] Open
Abstract
Many microorganisms use both biological and nonbiological molecules as sources of carbon and energy. This resourcefulness means that some microorganisms have mechanisms to assimilate pollutants found in the environment. One such organism is Comamonas testosteroni, which metabolizes 4-methylbenzenesulfonate and 4-methylbenzoate using the TsaMBCD pathway. TsaM is a Rieske oxygenase, which in concert with the reductase TsaB consumes a molar equivalent of NADH. Following this step, the annotated short-chain dehydrogenase/reductase and aldehyde dehydrogenase enzymes TsaC and TsaD each regenerate a molar equivalent of NADH. This co-occurrence ameliorates the need for stoichiometric addition of reducing equivalents and thus represents an attractive strategy for integration of Rieske oxygenase chemistry into biocatalytic applications. Therefore, in this work, to overcome the lack of information regarding NADH recycling enzymes that function in partnership with Rieske non-heme iron oxygenases (Rieske oxygenases), we solved the X-ray crystal structure of TsaC to a resolution of 2.18 Å. Using this structure, a series of substrate analog and protein variant combination reactions, and differential scanning fluorimetry experiments, we identified active site features involved in binding NAD+ and controlling substrate specificity. Further in vitro enzyme cascade experiments demonstrated the efficient TsaC- and TsaD-mediated regeneration of NADH to support Rieske oxygenase chemistry. Finally, through in-depth bioinformatic analyses, we illustrate the widespread co-occurrence of Rieske oxygenases with TsaC-like enzymes. This work thus demonstrates the utility of these NADH recycling enzymes and identifies a library of short-chain dehydrogenase/reductase enzyme prospects that can be used in Rieske oxygenase pathways for in situ regeneration of NADH.
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Affiliation(s)
- Jiayi Tian
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan, USA
| | - David G Boggs
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan, USA
| | - Patrick H Donnan
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan, USA
| | - Gage T Barroso
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan, USA
| | | | - Daniel P Dowling
- Department of Chemistry, University of Massachusetts Boston, Boston, Massachusetts, USA
| | - Joshua A Buss
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan, USA
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Mahto JK, Sharma M, Neetu N, Kayastha A, Aggarwal S, Kumar P. Conformational flexibility enables catalysis of phthalate cis-4,5-dihydrodiol dehydrogenase. Arch Biochem Biophys 2022; 727:109314. [DOI: 10.1016/j.abb.2022.109314] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2022] [Revised: 05/16/2022] [Accepted: 06/01/2022] [Indexed: 11/02/2022]
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Structural insights into dihydroxylation of terephthalate, a product of polyethylene terephthalate degradation. J Bacteriol 2022; 204:e0054321. [PMID: 35007143 DOI: 10.1128/jb.00543-21] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Biodegradation of terephthalate (TPA) is a highly desired catabolic process for the bacterial utilization of this Polyethylene terephthalate (PET) depolymerization product, but to date, the structure of terephthalate dioxygenase (TPDO), a Rieske oxygenase (RO) that catalyzes the dihydroxylation of TPA to a cis-diol is unavailable. In this study, we characterized the steady-state kinetics and first crystal structure of TPDO from Comamonas testosteroni KF1 (TPDOKF1). The TPDOKF1 exhibited the substrate specificity for TPA (kcat/Km = 57 ± 9 mM-1s-1). The TPDOKF1 structure harbors characteristics RO features as well as a unique catalytic domain that rationalizes the enzyme's function. The docking and mutagenesis studies reveal that its substrate specificity to TPA is mediated by Arg309 and Arg390 residues, two residues positioned on opposite faces of the active site. Additionally, residue Gln300 is also proven to be crucial for the activity, its substitution to alanine decreases the activity (kcat) by 80%. Together, this study delineates the structural features that dictate the substrate recognition and specificity of TPDO. Importance The global plastic pollution has become the most pressing environmental issue. Recent studies on enzymes depolymerizing polyethylene terephthalate plastic into terephthalate (TPA) show some potential in tackling this. Microbial utilization of this released product, TPA is an emerging and promising strategy for waste-to-value creation. Research from the last decade has discovered terephthalate dioxygenase (TPDO), as being responsible for initiating the enzymatic degradation of TPA in a few Gram-negative and Gram-positive bacteria. Here, we have determined the crystal structure of TPDO from Comamonas testosteroni KF1 and revealed that it possesses a unique catalytic domain featuring two basic residues in the active site to recognize TPA. Biochemical and mutagenesis studies demonstrated the crucial residues responsible for the substrate specificity of this enzyme.
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A poplar short-chain dehydrogenase reductase plays a potential key role in biphenyl detoxification. Proc Natl Acad Sci U S A 2021; 118:2103378118. [PMID: 34446553 PMCID: PMC8536390 DOI: 10.1073/pnas.2103378118] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Persistent organic pollutants (POPs), including polychlorinated biphenyls, represent a major environmental threat. Besides affecting human health, they negatively affect food security, pest and disease spread, carbon sequestration, biodiversity, and the resilience of ecosystems. Plant-based remediation offers important advantages over conventional remediation. However, limited knowledge of POP metabolism in planta can delay the application of molecular tools to genetically improve cleanup efficiency. By integrating functional and structural studies, we define here a plant-specific pathway which is activated by and possibly contributes to detoxifying biphenyl-derived toxicants. This pathway exhibits common features with bacterial biphenyl/PCB degradation but also significant differences. Our results open avenues to improve the success of phytoremediation technologies. Polychlorinated biphenyls (PCBs) are persistent organic pollutants with severe effects on human health and the biosphere. Plant-based remediation offers many benefits over conventional PCB remediation, but its development has been hampered by our poor understanding of biphenyl metabolism in eukaryotes, among other factors. We report here a major PCB-responsive protein in poplar, a plant model system capable of PCB uptake and translocation. We provide structural and functional evidence that this uncharacterized protein, termed SDR57C, belongs to the heterogeneous short-chain dehydrogenase reductase (SDR) superfamily. Despite sequence divergence, structural modeling hinted at structural and functional similarities between SDR57C and BphB, a central component of the Bph pathway for biphenyl/PCB degradation in aerobic bacteria. By combining gas chromatography/mass spectrometry (GC/MS) profiling with a functional complementation scheme, we found that poplar SDR57C can replace BphB activity in the upper Bph pathway of Pseudomonas furukawaii KF707 and therefore catalyze the oxidation of 2,3-dihydro-2,3-dihydroxybiphenyl (2,3-DHDB) to 2,3-dihydroxybiphenyl (2,3-DHB). Consistent with this biochemical activity, we propose a mechanism of action based on prior quantum studies, general properties of SDR enzymes, and the modeled docking of 2,3-DHDB to the SDR57C-NAD+ complex. The putative detoxifying capacity of SDR57C was substantiated through reverse genetics in Arabidopsis thaliana. Phenotypic characterization of the SDR lines underscored an inducible plant pathway with the potential to catabolize toxic biphenyl derivatives. Partial similarities with aerobic bacterial degradation notwithstanding, real-time messenger RNA quantification indicates the occurrence of plant-specific enzymes and features. Our results may help explain differences in degradative abilities among plant genotypes and also provide elements to improve them.
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Dhankhar P, Dalal V, Mahto JK, Gurjar BR, Tomar S, Sharma AK, Kumar P. Characterization of dye-decolorizing peroxidase from Bacillus subtilis. Arch Biochem Biophys 2020; 693:108590. [DOI: 10.1016/j.abb.2020.108590] [Citation(s) in RCA: 32] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2020] [Revised: 09/14/2020] [Accepted: 09/16/2020] [Indexed: 12/25/2022]
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Engineering Burkholderia xenovorans LB400 BphA through Site-Directed Mutagenesis at Position 283. Appl Environ Microbiol 2020; 86:AEM.01040-20. [PMID: 32709719 DOI: 10.1128/aem.01040-20] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2020] [Accepted: 07/15/2020] [Indexed: 11/20/2022] Open
Abstract
Biphenyl dioxygenase (BPDO), which is a Rieske-type oxygenase (RO), catalyzes the initial dioxygenation of biphenyl and some polychlorinated biphenyls (PCBs). In order to enhance the degradation ability of BPDO in terms of a broader substrate range, the BphAES283M, BphAEp4-S283M, and BphAERR41-S283M variants were created from the parent enzymes BphAELB400, BphAEp4, and BphAERR41, respectively, by a substitution at one residue, Ser283Met. The results of steady-state kinetic parameters show that for biphenyl, the k cat/Km values of BphAES283M, BphAEp4-S283M, and BphAERR41-S283M were significantly increased compared to those of their parent enzymes. Meanwhile, we determined the steady-state kinetics of BphAEs toward highly chlorinated biphenyls. The results suggested that the Ser283Met substitution enhanced the catalytic activity of BphAEs toward 2,3',4,4'-tetrachlorobiphenyl (2,3',4,4'-CB), 2,2',6,6'-tetrachlorobiphenyl (2,2',6,6'-CB), and 2,3',4,4',5-pentachlorobiphenyl (2,3',4,4',5-CB). We compared the catalytic reactions of BphAELB400 and its variants toward 2,2'-dichlorobiphenyl (2,2'-CB), 2,5-dichlorobiphenyl (2,5-CB), and 2,6-dichlorobiphenyl (2,6-CB). The biochemical data indicate that the Ser283Met substitution alters the orientation of the substrate inside the catalytic site and, thereby, its site of hydroxylation, and this was confirmed by docking experiments. We also assessed the substrate ranges of BphAELB400 and its variants with degradation activity. BphAES283M and BphAEp4-S283M were clearly improved in oxidizing some of the 3-6-chlorinated biphenyls, which are generally very poorly oxidized by most dioxygenases. Collectively, the present work showed a significant effect of mutation Ser283Met on substrate specificity/regiospecificity in BPDO. These will certainly be meaningful elements for understanding the effect of the residue corresponding to position 283 in other Rieske oxygenase enzymes.IMPORTANCE The segment from positions 280 to 283 in BphAEs is located at the entrance of the catalytic pocket, and it shows variation in conformation. In previous works, results have suggested but never proved that residue Ser283 of BphAELB400 might play a role in substrate specificity. In the present paper, we found that the Ser283Met substitution significantly increased the specificity of the reaction of BphAE toward biphenyl, 2,3',4,4'-CB, 2,2',6,6'-CB, and 2,3',4,4',5-CB. Meanwhile, the Ser283Met substitution altered the regiospecificity of BphAE toward 2,2'-dichlorobiphenyl and 2,6-dichlorobiphenyl. Additionally, this substitution extended the range of PCBs metabolized by the mutated BphAE. BphAES283M and BphAEp4-S283M were clearly improved in oxidizing some of the more highly chlorinated biphenyls (3 to 6 chlorines), which are generally very poorly oxidized by most dioxygenases. We used modeled and docked enzymes to identify some of the structural features that explain the new properties of the mutant enzymes. Altogether, the results of this study provide better insights into the mechanisms by which BPDO evolves to change and/or expand its substrate range and its regiospecificity.
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Wu X, Wu X, Shen L, Li J, Yu R, Liu Y, Qiu G, Zeng W. Whole Genome Sequencing and Comparative Genomics Analyses of Pandoraea sp. XY-2, a New Species Capable of Biodegrade Tetracycline. Front Microbiol 2019; 10:33. [PMID: 30761094 PMCID: PMC6361800 DOI: 10.3389/fmicb.2019.00033] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2018] [Accepted: 01/10/2019] [Indexed: 02/06/2023] Open
Abstract
Few bacteria are resistant to tetracycline and can even biodegrade tetracycline in the environment. In this study, we isolated a bacterium Pandoraea sp. XY-2, which could biodegrade 74% tetracycline at pH 7.0 and 30°C within 6 days. Thereafter, we determined the whole genome sequence of Pandoraea sp. XY-2 genome is a single circular chromosome of 5.06 Mb in size. Genomic annotation showed that two AA6 family members-encoding genes and nine glutathione S-transferase (GSTs)-encoding genes could be relevant to tetracycline biodegradation. In addition, the average nucleotide identities (ANI) analysis between the genomes of Pandoraea sp. XY-2 and other Pandoraea spp. revealed that Pandoraea sp. XY-2 belongs to a new species. Moreover, comparative genome analysis of 36 Pandoraea strains identified the pan and specific genes, numerous single nucleotide polymorphisms (SNPs), insertions, and deletion variations (InDels) and different syntenial relationships in the genome of Pandoraea sp. XY-2. Finally, the evolution and the origin analysis of genes related to tetracycline resistance revealed that the six tetA(48) genes and two specificgenes tetG and tetR in Pandoraea sp. XY-2 were acquired by horizontal gene transfer (HGT) events from sources related to Paraburkholderia, Burkholderia, Caballeronia, Salmonella, Vibrio, Proteobacteria, Pseudomonas, Acinetobacter, Flavimaricola, and some unidentified sources. As a new species, Pandoraea sp. XY-2 will be an excellent resource for the bioremediation of tetracycline-contaminated environment.
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Affiliation(s)
- Xueling Wu
- School of Minerals Processing and Bioengineering, Central South University, Changsha, China
- Key Laboratory of Biometallurgy, Ministry of Education, School of Minerals Processing and Bioengineering, Central South University, Changsha, China
| | - Xiaoyan Wu
- School of Minerals Processing and Bioengineering, Central South University, Changsha, China
| | - Li Shen
- School of Minerals Processing and Bioengineering, Central South University, Changsha, China
- Key Laboratory of Biometallurgy, Ministry of Education, School of Minerals Processing and Bioengineering, Central South University, Changsha, China
| | - Jiaokun Li
- School of Minerals Processing and Bioengineering, Central South University, Changsha, China
- Key Laboratory of Biometallurgy, Ministry of Education, School of Minerals Processing and Bioengineering, Central South University, Changsha, China
| | - Runlan Yu
- School of Minerals Processing and Bioengineering, Central South University, Changsha, China
- Key Laboratory of Biometallurgy, Ministry of Education, School of Minerals Processing and Bioengineering, Central South University, Changsha, China
| | - Yuandong Liu
- School of Minerals Processing and Bioengineering, Central South University, Changsha, China
- Key Laboratory of Biometallurgy, Ministry of Education, School of Minerals Processing and Bioengineering, Central South University, Changsha, China
| | - Guanzhou Qiu
- School of Minerals Processing and Bioengineering, Central South University, Changsha, China
- Key Laboratory of Biometallurgy, Ministry of Education, School of Minerals Processing and Bioengineering, Central South University, Changsha, China
| | - Weimin Zeng
- School of Minerals Processing and Bioengineering, Central South University, Changsha, China
- Key Laboratory of Biometallurgy, Ministry of Education, School of Minerals Processing and Bioengineering, Central South University, Changsha, China
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Zhang R, Shi X, Sun Y, Zhang Q, Wang W. Insights into the catalytic mechanism of dehydrogenase BphB: A quantum mechanics/molecular mechanics study. CHEMOSPHERE 2018; 208:69-76. [PMID: 29860146 DOI: 10.1016/j.chemosphere.2018.05.063] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/28/2018] [Revised: 05/10/2018] [Accepted: 05/11/2018] [Indexed: 06/08/2023]
Abstract
The present study delineated the dehydrogenation mechanism of cis-2,3-dihydro-2,3-dihydroxybiphenyl (2,3-DDBPH) and cis-2,3-dihydro-2,3-dihydroxy-4,4'-dichlorobiphenyl (2,3-DD-4,4'-DBPH) by Pandoraea pnomenusa strain B-356 cis-2,3-dihydro-2,3-dihydroxybiphenyl dehydrogenase (BphB) in atomistic detail. The enzymatic process was investigated by a combined quantum mechanics/molecular mechanics (QM/MM) approach. Five different snapshots were extracted and calculated, which revealed that the Boltzmann-weighted average barriers of 2,3-DDBPH and 2,3-DD-4,4'-DBPH dehydrogenation processes are 10.7 and 11.5 kcal mol-1, respectively. The established dehydrogenation mechanism provides new insight into the degradation processes of other chlorinated 2,3-DDBPH. In addition to Asn115, Ser142, and Lys149, the importance of Ile 89, Asn143, Pro184, Met 187, Thr189, and Lue 191 during the dehydrogenation process of 2,3-DDBPH and 2,3-DD-4,4'-DBPH were also highlighted to search for promising mutation targets for improving the catalytic efficiency of BphB.
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Affiliation(s)
- Ruiming Zhang
- Environment Research Institute, Shandong University, Jinan, 250100, PR China
| | - Xiangli Shi
- Environment Research Institute, Shandong University, Jinan, 250100, PR China
| | - Yanhui Sun
- College of Environment and Safety Engineering, Qingdao University of Science and Technology, Qingdao, 266042, PR China
| | - Qingzhu Zhang
- Environment Research Institute, Shandong University, Jinan, 250100, PR China.
| | - Wenxing Wang
- Environment Research Institute, Shandong University, Jinan, 250100, PR China
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Park AK, Kim H, Kim IS, Roh SJ, Shin SC, Lee JH, Park H, Kim HW. Crystal structure of cis-dihydrodiol naphthalene dehydrogenase (NahB) from Pseudomonas sp. MC1: Insights into the early binding process of the substrate. Biochem Biophys Res Commun 2017; 491:403-408. [PMID: 28728845 DOI: 10.1016/j.bbrc.2017.07.089] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2017] [Accepted: 07/14/2017] [Indexed: 10/19/2022]
Abstract
The bacterial strain Pseudomonas sp. MC1 harbors an 81-kb metabolic plasmid, which encodes enzymes involved in the conversion of naphthalene to salicylate. Of these, the enzyme NahB (cis-dihydrodiol naphthalene dehydrogenase), which catalyzes the second reaction of this pathway, binds to various substrates such as cis-1,2-dihydro-1,2-dihydroxy-naphthalene (1,2-DDN), cis-2,3-dihydro-2,3-dihydroxybiphenyl (2,3-DDB), and 3,4-dihydro-3,4-dihydroxy-2,2',5,5'-tetrachlorobiphenyl (3,4-DD-2,2',5-5-TCB). However, the mechanism underlying its broad substrate specificity is unclear owing to the lack of structural information. Here, we determined the first crystal structures of NahB in the absence and presence of NAD+ and 2,3-dihydroxybiphenyl (2,3-DB). Structure analysis suggests that the flexible substrate-binding loop allows NahB to accommodate diverse substrates. Furthermore, we defined the initial steps of substrate recognition and identified the early substrate-binding site in the substrate recognition process through the complex structure with ligands.
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Affiliation(s)
- Ae Kyung Park
- Unit of Polar Genomics, Korea Polar Research Institute, Incheon 21990, South Korea
| | - Hyun Kim
- Unit of Polar Genomics, Korea Polar Research Institute, Incheon 21990, South Korea
| | - Il-Sup Kim
- School of Life Sciences, BK21 Plus KNU Creative BioResearch Group, Kyungpook National University, Daegu 41566, South Korea
| | - Soo Jung Roh
- Unit of Polar Genomics, Korea Polar Research Institute, Incheon 21990, South Korea; Evolutionary Genomics Laboratory, Department of Biological Sciences, Inha University, 100 Inha-ro, Nam-gu, Incheon, 22212, South Korea
| | - Seung Chul Shin
- Unit of Polar Genomics, Korea Polar Research Institute, Incheon 21990, South Korea
| | - Jun Hyuck Lee
- Unit of Polar Genomics, Korea Polar Research Institute, Incheon 21990, South Korea; Department of Polar Sciences, University of Science and Technology, Incheon 21990, South Korea
| | - Hyun Park
- Unit of Polar Genomics, Korea Polar Research Institute, Incheon 21990, South Korea; Department of Polar Sciences, University of Science and Technology, Incheon 21990, South Korea
| | - Han-Woo Kim
- Unit of Polar Genomics, Korea Polar Research Institute, Incheon 21990, South Korea; Department of Polar Sciences, University of Science and Technology, Incheon 21990, South Korea.
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Binding of NADP + triggers an open-to-closed transition in a mycobacterial FabG β-ketoacyl-ACP reductase. Biochem J 2017; 474:907-921. [PMID: 28126742 DOI: 10.1042/bcj20161052] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2016] [Revised: 01/11/2017] [Accepted: 01/25/2017] [Indexed: 02/07/2023]
Abstract
The ketoacyl-acyl carrier protein (ACP) reductase FabG catalyzes the NADPH/NADH dependent reduction of β-ketoacyl-ACP substrates to β-hydroxyacyl-ACP products, the first reductive step in the fatty acid biosynthesis elongation cycle. FabG proteins are ubiquitous in bacteria and are part of the type II fatty acid synthase system. Mining the Mycobacterium smegmatis genome uncovered several putative FabG-like proteins. Among them, we identified M. smegmatis MSMEG_6753 whose gene was found adjacent to MSMEG_6754, encoding a recently characterized enoyl-CoA dehydratase, and to MSMEG_6755, encoding another potential reductase. Recombinantly expressed and purified MSMEG_6753 exhibits ketoacyl reductase activity in the presence of acetoacetyl-CoA and NADPH. This activity was subsequently confirmed by functional complementation studies in a fabG thermosensitive Escherichia coli mutant. Furthermore, comparison of the apo and the NADP+-bound MSMEG_6753 crystal structures showed that cofactor binding induces a closed conformation of the protein. A ΔMSMEG_6753 deletion mutant could be generated in M. smegmatis, indicating that this gene is dispensable for mycobacterial growth. Overall, these results showcase the diversity of FabG-like proteins in mycobacteria and new structural features regarding the catalytic mechanism of this important family of enzymes that may be of importance for the rational design of specific FabG inhibitors.
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Haft DH, Pierce PG, Mayclin SJ, Sullivan A, Gardberg AS, Abendroth J, Begley DW, Phan IQ, Staker BL, Myler PJ, Marathias VM, Lorimer DD, Edwards TE. Mycofactocin-associated mycobacterial dehydrogenases with non-exchangeable NAD cofactors. Sci Rep 2017; 7:41074. [PMID: 28120876 PMCID: PMC5264612 DOI: 10.1038/srep41074] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2016] [Accepted: 12/12/2016] [Indexed: 01/08/2023] Open
Abstract
During human infection, Mycobacterium tuberculosis (Mtb) survives the normally bacteriocidal phagosome of macrophages. Mtb and related species may be able to combat this harsh acidic environment which contains reactive oxygen species due to the mycobacterial genomes encoding a large number of dehydrogenases. Typically, dehydrogenase cofactor binding sites are open to solvent, which allows NAD/NADH exchange to support multiple turnover. Interestingly, mycobacterial short chain dehydrogenases/reductases (SDRs) within family TIGR03971 contain an insertion at the NAD binding site. Here we present crystal structures of 9 mycobacterial SDRs in which the insertion buries the NAD cofactor except for a small portion of the nicotinamide ring. Line broadening and STD-NMR experiments did not show NAD or NADH exchange on the NMR timescale. STD-NMR demonstrated binding of the potential substrate carveol, the potential product carvone, the inhibitor tricyclazol, and an external redox partner 2,6-dichloroindophenol (DCIP). Therefore, these SDRs appear to contain a non-exchangeable NAD cofactor and may rely on an external redox partner, rather than cofactor exchange, for multiple turnover. Incidentally, these genes always appear in conjunction with the mftA gene, which encodes the short peptide MftA, and with other genes proposed to convert MftA into the external redox partner mycofactocin.
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Affiliation(s)
- Daniel H Haft
- National Institutes of Health (NIH), Bethesda, MD 20892, USA
| | - Phillip G Pierce
- Seattle Structural Genomics Center for Infectious Disease (SSGCID), Seattle, WA 98109, USA.,Beryllium Discovery Corp., 7869 NE Day Road West, Bainbridge Island, WA 98110, USA
| | - Stephen J Mayclin
- Seattle Structural Genomics Center for Infectious Disease (SSGCID), Seattle, WA 98109, USA.,Beryllium Discovery Corp., 7869 NE Day Road West, Bainbridge Island, WA 98110, USA
| | - Amy Sullivan
- Seattle Structural Genomics Center for Infectious Disease (SSGCID), Seattle, WA 98109, USA.,Beryllium Discovery Corp., 7869 NE Day Road West, Bainbridge Island, WA 98110, USA
| | - Anna S Gardberg
- Seattle Structural Genomics Center for Infectious Disease (SSGCID), Seattle, WA 98109, USA.,Beryllium Discovery Corp., 7869 NE Day Road West, Bainbridge Island, WA 98110, USA
| | - Jan Abendroth
- Seattle Structural Genomics Center for Infectious Disease (SSGCID), Seattle, WA 98109, USA.,Beryllium Discovery Corp., 7869 NE Day Road West, Bainbridge Island, WA 98110, USA
| | - Darren W Begley
- Seattle Structural Genomics Center for Infectious Disease (SSGCID), Seattle, WA 98109, USA.,Beryllium Discovery Corp., 7869 NE Day Road West, Bainbridge Island, WA 98110, USA
| | - Isabelle Q Phan
- Seattle Structural Genomics Center for Infectious Disease (SSGCID), Seattle, WA 98109, USA.,Center for Infectious Disease Research (formerly Seattle Biomedical Research Institute), 307 Westlake Avenue North, Seattle WA 98109, USA
| | - Bart L Staker
- Seattle Structural Genomics Center for Infectious Disease (SSGCID), Seattle, WA 98109, USA.,Center for Infectious Disease Research (formerly Seattle Biomedical Research Institute), 307 Westlake Avenue North, Seattle WA 98109, USA
| | - Peter J Myler
- Seattle Structural Genomics Center for Infectious Disease (SSGCID), Seattle, WA 98109, USA.,Center for Infectious Disease Research (formerly Seattle Biomedical Research Institute), 307 Westlake Avenue North, Seattle WA 98109, USA.,University of Washington, Department of Medical Education and Biomedical Informatics &Department of Global Health, Seattle WA 98195, USA
| | - Vasilios M Marathias
- Seattle Structural Genomics Center for Infectious Disease (SSGCID), Seattle, WA 98109, USA.,Beryllium Discovery Corp., 7869 NE Day Road West, Bainbridge Island, WA 98110, USA
| | - Donald D Lorimer
- Seattle Structural Genomics Center for Infectious Disease (SSGCID), Seattle, WA 98109, USA.,Beryllium Discovery Corp., 7869 NE Day Road West, Bainbridge Island, WA 98110, USA
| | - Thomas E Edwards
- Seattle Structural Genomics Center for Infectious Disease (SSGCID), Seattle, WA 98109, USA.,Beryllium Discovery Corp., 7869 NE Day Road West, Bainbridge Island, WA 98110, USA
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13
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Costa DMA, Costa MAF, Guimarães SL, Coitinho JB, Gómez SV, Brandão TADS, Nagem RAP. A combined approach for enhancing the stability of recombinant cis-dihydrodiol naphthalene dehydrogenase from Pseudomonas putida G7 allowed for the structural and kinetic characterization of the enzyme. Protein Expr Purif 2017; 132:50-59. [PMID: 28089880 DOI: 10.1016/j.pep.2017.01.005] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2016] [Revised: 12/09/2016] [Accepted: 01/08/2017] [Indexed: 11/29/2022]
Abstract
The second enzyme of the naphthalene degradation pathway in Pseudomonas putida G7 is NahB, a dehydrogenase that converts cis-1,2-dihydroxy-1,2-dihydronaphthalene to 1,2-dihydroxynaphthalene. We report the cloning, optimization of expression, purification, kinetic studies and preliminary structural characterization of the recombinant NahB. The nahB gene was cloned into a T7 expression vector and the enzyme was overexpressed in Escherichia coli Rosetta (DE3) as an N-terminal hexa-histidine-tagged protein (6xHis-NahB). Using methods of enhancing protein stability in solution, we tested different expression, cell lysis, and purification protocols with and without ligand supplementation. The protein stability was evaluated by dynamic light scattering and circular dichroism spectroscopy assays. Best-derived protocols (expression at 18 °C, cell lysis with homogenizer, and three purification steps) were used to produce 20 mg of homogeneous 6xHis-NahB per liter of culture. The secondary and quaternary structures of 6xHis-NahB were assessed by circular dichroism and size-exclusion chromatography experiments, respectively. The enzyme was NAD+-dependent and active at pH 7.0 and 9.4 for the oxidation of the substrate. The Michaelis-Menten parameters determined at pH 7.0 and 25 °C for the substrate and cofactor, presented respective Km values of 6 and 350 μM, and a kcat value of 8.3 s-1. Furthermore, we identified conditions for the crystallization of 6xHis-NahB. X-ray diffraction data were collected from a single 6xHis-NahB crystal which diffracted to 2.21 Å. The crystal belongs to space group I222, with unit-cell parameters a = 63.62, b = 69.50, and c = 117.47 Å. The tertiary structure of 6xHis-NahB was determined using the molecular replacement method. Further structural refinement is currently underway.
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Affiliation(s)
- Débora Maria Abrantes Costa
- Departamento de Bioquímica e Imunologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Avenida Antônio Carlos 6627, Belo Horizonte, MG, CEP 31270-901, Brazil
| | - Mariana Amalia Figueiredo Costa
- Departamento de Bioquímica e Imunologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Avenida Antônio Carlos 6627, Belo Horizonte, MG, CEP 31270-901, Brazil
| | - Samuel Leite Guimarães
- Departamento de Bioquímica e Imunologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Avenida Antônio Carlos 6627, Belo Horizonte, MG, CEP 31270-901, Brazil
| | - Juliana Barbosa Coitinho
- Departamento de Bioquímica e Imunologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Avenida Antônio Carlos 6627, Belo Horizonte, MG, CEP 31270-901, Brazil
| | - Stefanya Velásquez Gómez
- Departamento de Química, Instituto de Ciências Exatas, Universidade Federal de Minas Gerais, Avenida Antônio Carlos 6627, Belo Horizonte, MG, CEP 31270-901, Brazil
| | - Tiago Antônio da Silva Brandão
- Departamento de Química, Instituto de Ciências Exatas, Universidade Federal de Minas Gerais, Avenida Antônio Carlos 6627, Belo Horizonte, MG, CEP 31270-901, Brazil
| | - Ronaldo Alves Pinto Nagem
- Departamento de Bioquímica e Imunologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Avenida Antônio Carlos 6627, Belo Horizonte, MG, CEP 31270-901, Brazil.
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14
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Structural Basis of the Enhanced Pollutant-Degrading Capabilities of an Engineered Biphenyl Dioxygenase. J Bacteriol 2016; 198:1499-512. [PMID: 26953337 DOI: 10.1128/jb.00952-15] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2015] [Accepted: 02/25/2016] [Indexed: 11/20/2022] Open
Abstract
UNLABELLED Biphenyl dioxygenase, the first enzyme of the biphenyl catabolic pathway, is a major determinant of which polychlorinated biphenyl (PCB) congeners are metabolized by a given bacterial strain. Ongoing efforts aim to engineer BphAE, the oxygenase component of the enzyme, to efficiently transform a wider range of congeners. BphAEII9, a variant of BphAELB400 in which a seven-residue segment, (335)TFNNIRI(341), has been replaced by the corresponding segment of BphAEB356, (333)GINTIRT(339), transforms a broader range of PCB congeners than does either BphAELB400 or BphAEB356, including 2,6-dichlorobiphenyl, 3,3'-dichlorobiphenyl, 4,4'-dichlorobiphenyl, and 2,3,4'-trichlorobiphenyl. To understand the structural basis of the enhanced activity of BphAEII9, we have determined the three-dimensional structure of this variant in substrate-free and biphenyl-bound forms. Structural comparison with BphAELB400 reveals a flexible active-site mouth and a relaxed substrate binding pocket in BphAEII9 that allow it to bind different congeners and which could be responsible for the enzyme's altered specificity. Biochemical experiments revealed that BphAEII9 transformed 2,3,4'-trichlorobiphenyl and 2,2',5,5'-tetrachlorobiphenyl more efficiently than did BphAELB400 and BphAEB356 BphAEII9 also transformed the insecticide dichlorodiphenyltrichloroethane (DDT) more efficiently than did either parental enzyme (apparent kcat/Km of 2.2 ± 0.5 mM(-1) s(-1), versus 0.9 ± 0.5 mM(-1) s(-1) for BphAEB356). Studies of docking of the enzymes with these three substrates provide insight into the structural basis of the different substrate selectivities and regiospecificities of the enzymes. IMPORTANCE Biphenyl dioxygenase is the first enzyme of the biphenyl degradation pathway that is involved in the degradation of polychlorinated biphenyls. Attempts have been made to identify the residues that influence the enzyme activity for the range of substrates among various species. In this study, we have done a structural study of one variant of this enzyme that was produced by family shuffling of genes from two different species. Comparison of the structure of this variant with those of the parent enzymes provided an important insight into the molecular basis for the broader substrate preference of this enzyme. The structural and functional details gained in this study can be utilized to further engineer desired enzymatic activity, producing more potent enzymes.
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15
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Lim YL, Ee R, How KY, Lee SK, Yong D, Tee KK, Yin WF, Chan KG. Complete genome sequencing of Pandoraea pnomenusa RB38 and Molecular Characterization of Its N-acyl homoserine lactone synthase gene ppnI. PeerJ 2015; 3:e1225. [PMID: 26336650 PMCID: PMC4556143 DOI: 10.7717/peerj.1225] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2015] [Accepted: 08/11/2015] [Indexed: 01/05/2023] Open
Abstract
In this study, we sequenced the genome of Pandoraea pnomenusa RB38 using Pacific Biosciences RSII (PacBio) Single Molecule Real Time (SMRT) sequencing technology. A pair of cognate luxI/R homologs was identified where the luxI homolog, ppnI, was found adjacent to a luxR homolog, ppnR1. An additional orphan luxR homolog, ppnR2, was also discovered. Multiple sequence alignment and phylogenetic analysis revealed that ppnI is an N-acyl homoserine lactone (AHL) synthase gene that is distinct from those of the nearest phylogenetic neighbor viz. Burkholderia spp. High resolution tandem mass spectrometry (LC-MS/MS) analysis showed that Escherichia coli BL21 harboring ppnI produced a similar AHL profile (N-octanoylhomoserine lactone, C8-HSL) as P. pnomenusa RB38, the wild-type donor strain, confirming that PpnI directed the synthesis of AHL in P. pnomenusa RB38. To our knowledge, this is the first documentation of the luxI/R homologs of the genus Pandoraea.
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Affiliation(s)
- Yan-Lue Lim
- Division of Genetics and Molecular Biology, Faculty of Science, Institute of Biological Sciences, University of Malaya , Kuala Lumpur , Malaysia
| | - Robson Ee
- Division of Genetics and Molecular Biology, Faculty of Science, Institute of Biological Sciences, University of Malaya , Kuala Lumpur , Malaysia
| | - Kah-Yan How
- Division of Genetics and Molecular Biology, Faculty of Science, Institute of Biological Sciences, University of Malaya , Kuala Lumpur , Malaysia
| | - Siew-Kim Lee
- Division of Genetics and Molecular Biology, Faculty of Science, Institute of Biological Sciences, University of Malaya , Kuala Lumpur , Malaysia
| | - Delicia Yong
- Department of Medicine, Faculty of Medicine, University of Malaya , Kuala Lumpur , Malaysia
| | - Kok Keng Tee
- Department of Medicine, Faculty of Medicine, University of Malaya , Kuala Lumpur , Malaysia
| | - Wai-Fong Yin
- Division of Genetics and Molecular Biology, Faculty of Science, Institute of Biological Sciences, University of Malaya , Kuala Lumpur , Malaysia
| | - Kok-Gan Chan
- Division of Genetics and Molecular Biology, Faculty of Science, Institute of Biological Sciences, University of Malaya , Kuala Lumpur , Malaysia
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16
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Boyd DR, Sharma ND, Berberian MV, Cleij M, Hardacre C, Ljubez V, McConville G, Stevenson PJ, Kulakov LA, Allen CCR. Arenecis-Diol Dehydrogenase-Catalysed Regio- and Stereoselective Oxidation of Arene-, Cycloalkane- and Cycloalkene-cis-diols to Yield Catechols and Chiral α-Ketols. Adv Synth Catal 2015. [DOI: 10.1002/adsc.201500189] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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17
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Dynamic characterization and substrate binding of cis-2,3-dihydrobiphenyl-2,3-diol dehydrogenase—an enzyme used in bioremediation. J Mol Model 2014; 20:2531. [DOI: 10.1007/s00894-014-2531-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2014] [Accepted: 11/12/2014] [Indexed: 10/24/2022]
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18
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Tian JH, Pourcher AM, Bouchez T, Gelhaye E, Peu P. Occurrence of lignin degradation genotypes and phenotypes among prokaryotes. Appl Microbiol Biotechnol 2014; 98:9527-44. [PMID: 25343973 DOI: 10.1007/s00253-014-6142-4] [Citation(s) in RCA: 77] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2014] [Revised: 10/06/2014] [Accepted: 10/07/2014] [Indexed: 11/24/2022]
Abstract
A number of prokaryotes actively contribute to lignin degradation in nature and their activity could be of interest for many applications including the production of biogas/biofuel from lignocellulosic biomass and biopulping. This review compares the reliability and efficiency of the culture-dependent screening methods currently used for the isolation of ligninolytic prokaryotes. Isolated prokaryotes exhibiting lignin-degrading potential are presented according to their phylogenetic groups. With the development of bioinformatics, culture-independent techniques are emerging that allow larger-scale data mining for ligninolytic prokaryotic functions but today, these techniques still have some limits. In this work, two phylogenetic affiliations of isolated prokaryotes exhibiting ligninolytic potential and laccase-encoding prokaryotes were determined on the basis of 16S rDNA sequences, providing a comparative view of results obtained by the two types of screening techniques. The combination of laboratory culture and bioinformatics approaches is a promising way to explore lignin-degrading prokaryotes.
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Affiliation(s)
- Jiang-Hao Tian
- IRSTEA, UR GERE, 17 avenue de Cucillé, CS 64427, 35044, Rennes, France
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19
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Han-Jen RE, Wai-Fong Y, Kok-Gan C. Pandoraea sp. RB-44, a novel quorum sensing soil bacterium. SENSORS 2013; 13:14121-32. [PMID: 24145919 PMCID: PMC3859112 DOI: 10.3390/s131014121] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/26/2013] [Revised: 09/20/2013] [Accepted: 09/30/2013] [Indexed: 11/16/2022]
Abstract
Proteobacteria are known to communicate via signaling molecules and this process is known as quorum sensing. The most commonly studied quorum sensing molecules are N-acylhomoserine lactones (AHLs) that consists of a homoserine lactone moiety and an N-acyl side chain with various chain lengths and degrees of saturation at the C-3 position. We have isolated a bacterium, RB-44, from a site which was formally a landfill dumping ground. Using matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometry analysis, this isolate was identified as a Pandoraea sp.which was then screened for AHL production using biosensors which indicated its quorum sensing properties. To identify the AHL profile of Pandoraea sp. RB-44, we used high resolution tandem mass spectrometry confirming that this isolate produced N-octanoylhomoserine lactone (C8-HSL). To the best of our knowledge, this is the first report that showed quorum sensing activity exhibited by Pandoraea sp. Our data add Pandoraea sp. to the growing number of bacteria that possess QS systems.
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Affiliation(s)
- Robson Ee Han-Jen
- Division of Genetics and Molecular Biology, Institute of Biological Sciences, Faculty of Science, University of Malaya, 50603 Kuala Lumpur, Malaysia.
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Has the bacterial biphenyl catabolic pathway evolved primarily to degrade biphenyl? The diphenylmethane case. J Bacteriol 2013; 195:3563-74. [PMID: 23749969 DOI: 10.1128/jb.00161-13] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
In this work, we have compared the ability of Pandoraea pnomenusa B356 and of Burkholderia xenovorans LB400 to metabolize diphenylmethane and benzophenone, two biphenyl analogs in which the phenyl rings are bonded to a single carbon. Both chemicals are of environmental concern. P. pnomenusa B356 grew well on diphenylmethane. On the basis of growth kinetics analyses, diphenylmethane and biphenyl were shown to induce the same catabolic pathway. The profile of metabolites produced during growth of strain B356 on diphenylmethane was the same as the one produced by isolated enzymes of the biphenyl catabolic pathway acting individually or in coupled reactions. The biphenyl dioxygenase oxidizes diphenylmethane to 3-benzylcyclohexa-3,5-diene-1,2-diol very efficiently, and ultimately this metabolite is transformed to phenylacetic acid, which is further metabolized by a lower pathway. Strain B356 was also able to cometabolize benzophenone through its biphenyl pathway, although in this case, this substrate was unable to induce the biphenyl catabolic pathway and the degradation was incomplete, with accumulation of 2-hydroxy-6,7-dioxo-7-phenylheptanoic acid. Unlike strain B356, B. xenovorans LB400 did not grow on diphenylmethane. Its biphenyl pathway enzymes metabolized diphenylmethane, but they poorly metabolize benzophenone. The fact that the biphenyl catabolic pathway of strain B356 metabolized diphenylmethane and benzophenone more efficiently than that of strain LB400 brings us to postulate that in strain B356, this pathway evolved divergently to serve other functions not related to biphenyl degradation.
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21
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Hwang CC, Chang YH, Lee HJ, Wang TP, Su YM, Chen HW, Liang PH. The catalytic roles of P185 and T188 and substrate-binding loop flexibility in 3α-hydroxysteroid dehydrogenase/carbonyl reductase from Comamonas testosteroni. PLoS One 2013; 8:e63594. [PMID: 23717450 PMCID: PMC3662788 DOI: 10.1371/journal.pone.0063594] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2013] [Accepted: 04/04/2013] [Indexed: 11/18/2022] Open
Abstract
3α-Hydroxysteroid dehydrogenase/carbonyl reductase from Comamonas testosteroni reversibly catalyzes the oxidation of androsterone with NAD(+) to form androstanedione and NADH. Structurally the substrate-binding loop of the residues, T188-K208, is unresolved, while binding with NAD(+) causes the appearance of T188-P191 in the binary complex. This study determines the functional roles of the flexible substrate-binding loop in conformational changes and enzyme catalysis. A stopped-flow study reveals that the rate-limiting step in the reaction is the release of the NADH. The mutation at P185 in the hinge region and T188 in the loop causes a significant increase in the Kd value for NADH by fluorescence titration. A kinetic study of the mutants of P185A, P185G, T188A and T188S shows an increase in k(cat), K(androsterone) and K(iNAD) and equal primary isotope effects of (D)V and (D) (V/K). Therefore, these mutants increase the dissociation of the nucleotide cofactor, thereby increasing the rate of release of the product and producing the rate-limiting step in the hydride transfer. Simulated molecular modeling gives results that are consistent with the conformational change in the substrate-binding loop after NAD(+) binding. These results indicate that P185, T188 and the flexible substrate-binding loop are involved in binding with the nucleotide cofactor and with androsterone and are also involved in catalysis.
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Affiliation(s)
- Chi-Ching Hwang
- Department of Biochemistry, Faculty of Medicine, College of Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan.
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22
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Sylvestre M. Prospects for using combined engineered bacterial enzymes and plant systems to rhizoremediate polychlorinated biphenyls. Environ Microbiol 2012; 15:907-15. [PMID: 23106850 DOI: 10.1111/1462-2920.12007] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2012] [Revised: 09/06/2012] [Accepted: 09/26/2012] [Indexed: 01/17/2023]
Abstract
The fate of polychlorinated biphenyls (PCBs) in soil is driven by a combination of interacting biological processes. Several investigations have brought evidence that the rhizosphere provides a remarkable ecological niche to enhance the PCB degradation process by rhizobacteria. The bacterial oxidative enzymes involved in PCB degradation have been investigated extensively and novel engineered enzymes exhibiting enhanced catalytic activities toward more persistent PCBs have been described. Furthermore, recent studies suggest that approaches involving processes based on plant-microbe associations are very promising to remediate PCB-contaminated sites. In this review emphasis will be placed on the current state of knowledge regarding the strategies that are proposed to engineer the enzymes of the PCB-degrading bacterial oxidative pathway and to design PCB-degrading plant-microbe systems to remediate PCB-contaminated soil.
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Affiliation(s)
- Michel Sylvestre
- Institut National de la Recherche Scientifique, INRS-Instittut Armand-Frappier, Laval, Quebec, Canada, H7V1B7.
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