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Lin ES, Huang YH, Yang PC, Peng WF, Huang CY. Complexed Crystal Structure of the Dihydroorotase Domain of Human CAD Protein with the Anticancer Drug 5-Fluorouracil. Biomolecules 2023; 13:149. [PMID: 36671534 PMCID: PMC9856072 DOI: 10.3390/biom13010149] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2022] [Revised: 01/05/2023] [Accepted: 01/09/2023] [Indexed: 01/13/2023] Open
Abstract
Dihydroorotase (DHOase) is the third enzyme in the pathway used for the biosynthesis of pyrimidine nucleotides. In mammals, DHOase is active in a trifunctional enzyme, CAD, which also carries out the activities of carbamoyl phosphate synthetase and aspartate transcarbamoylase. Prior to this study, it was unknown whether the FDA-approved clinical drug 5-fluorouracil (5-FU), which is used as an anticancer therapy, could bind to the DHOase domain of human CAD (huDHOase). Here, we identified huDHOase as a new 5-FU binding protein, thereby extending the 5-FU interactome to this human enzyme. In order to investigate where 5-FU binds to huDHOase, we solved the complexed crystal structure at 1.97 Å (PDB ID 8GVZ). The structure of huDHOase complexed with malate was also determined for the sake of comparison (PDB ID 8GW0). These two nonsubstrate ligands were bound at the active site of huDHOase. It was previously established that the substrate N-carbamoyl-L-aspartate is either bound to or moves away from the active site, but it is the loop that is extended towards (loop-in mode) or moved away (loop-out mode) from the active site. DHOase also binds to nonsubstrate ligands via the loop-out mode. In contrast to the Escherichia coli DHOase model, our complexed structures revealed that huDHOase binds to either 5-FU or malate via the loop-in mode. We further characterized the binding of 5-FU to huDHOase using site-directed mutagenesis and the fluorescence quenching method. Considering the loop-in mode, the dynamic loop in huDHOase should be a suitable drug-targeting site for further designing inhibitors and clinical chemotherapies to suppress pyrimidine biosynthesis in cancer cell lines.
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Affiliation(s)
- En-Shyh Lin
- Department of Beauty Science, National Taichung University of Science and Technology, Taichung City 403, Taiwan
| | - Yen-Hua Huang
- Department of Beauty Science, National Taichung University of Science and Technology, Taichung City 403, Taiwan
- Department of Biomedical Sciences, Chung Shan Medical University, Taichung City 402, Taiwan
| | - Po-Chun Yang
- Department of Biomedical Sciences, Chung Shan Medical University, Taichung City 402, Taiwan
| | - Wei-Feng Peng
- Department of Biomedical Sciences, Chung Shan Medical University, Taichung City 402, Taiwan
- Department of Medicine, College of Medicine, Chung Shan Medical University, Taichung City 402, Taiwan
- Department of Pediatrics, National Taiwan University Children’s Hospital, Taipei 100, Taiwan
| | - Cheng-Yang Huang
- Department of Biomedical Sciences, Chung Shan Medical University, Taichung City 402, Taiwan
- Department of Medical Research, Chung Shan Medical University Hospital, Taichung City 402, Taiwan
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Vitali J, Nix JC, Newman HE, Colaneri MJ. Crystal structure of Methanococcus jannaschii dihydroorotase. Proteins 2023; 91:91-98. [PMID: 35978488 PMCID: PMC9771888 DOI: 10.1002/prot.26412] [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: 04/29/2022] [Revised: 08/02/2022] [Accepted: 08/11/2022] [Indexed: 12/24/2022]
Abstract
In this paper, we report the structural analysis of dihydroorotase (DHOase) from the hyperthermophilic and barophilic archaeon Methanococcus jannaschii. DHOase catalyzes the reversible cyclization of N-carbamoyl-l-aspartate to l-dihydroorotate in the third step of de novo pyrimidine biosynthesis. DHOases form a very diverse family of enzymes and have been classified into types and subtypes with structural similarities and differences among them. This is the first archaeal DHOase studied by x-ray diffraction. Its structure and comparison with known representatives of the other subtypes help define the structural features of the archaeal subtype. The M. jannaschii DHOase is found here to have traits from all subtypes. Contrary to expectations, it has a carboxylated lysine bridging the two Zn ions in the active site, and a long catalytic loop. It is a monomeric protein with a large β sandwich domain adjacent to the TIM barrel. Loop 5 is similar to bacterial type III and the C-terminal extension is long.
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Affiliation(s)
- Jacqueline Vitali
- Department of PhysicsCleveland State UniversityClevelandOhioUSA
- Department of Biological, Geological and Environmental SciencesCleveland State UniversityClevelandOhioUSA
| | - Jay C. Nix
- Molecular Biology Consortium, Advanced Light SourceLawrence Berkeley National LaboratoryBerkeleyCaliforniaUSA
| | - Haley E. Newman
- Department of Biological, Geological and Environmental SciencesCleveland State UniversityClevelandOhioUSA
| | - Michael J. Colaneri
- Department of Chemistry and PhysicsThe State University of New York CollegeOld WestburyNew YorkUSA
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Guan HH, Huang YH, Lin ES, Chen CJ, Huang CY. Structural Analysis of Saccharomyces cerevisiae Dihydroorotase Reveals Molecular Insights into the Tetramerization Mechanism. Molecules 2021; 26:molecules26237249. [PMID: 34885830 PMCID: PMC8659124 DOI: 10.3390/molecules26237249] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2021] [Revised: 11/26/2021] [Accepted: 11/27/2021] [Indexed: 11/16/2022] Open
Abstract
Dihydroorotase (DHOase), a dimetalloenzyme containing a carbamylated lysine within the active site, is a member of the cyclic amidohydrolase family, which also includes allantoinase (ALLase), dihydropyrimidinase (DHPase), hydantoinase, and imidase. Unlike most known cyclic amidohydrolases, which are tetrameric, DHOase exists as a monomer or dimer. Here, we report and analyze two crystal structures of the eukaryotic Saccharomyces cerevisiae DHOase (ScDHOase) complexed with malate. The structures of different DHOases were also compared. An asymmetric unit of these crystals contained four crystallographically independent ScDHOase monomers. ScDHOase shares structural similarity with Escherichia coli DHOase (EcDHOase). Unlike EcDHOase, ScDHOase can form tetramers, both in the crystalline state and in solution. In addition, the subunit-interacting residues of ScDHOase for dimerization and tetramerization are significantly different from those of other DHOases. The tetramerization pattern of ScDHOase is also different from those of DHPase and ALLase. Based on sequence analysis and structural evidence, we identify two unique helices (α6 and α10) and a loop (loop 7) for tetramerization, and discuss why the residues for tetramerization in ScDHOase are not necessarily conserved among DHOases.
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Affiliation(s)
- Hong-Hsiang Guan
- Life Science Group, Scientific Research Division, National Synchrotron Radiation Research Center, Hsinchu 33076, Taiwan;
| | - Yen-Hua Huang
- School of Biomedical Sciences, Chung Shan Medical University, No.110, Sec.1, Chien-Kuo N. Rd., Taichung City 402, Taiwan;
| | - En-Shyh Lin
- Department of Beauty Science, National Taichung University of Science and Technology, No.193, Sec.1, San-Min Rd., Taichung City 403, Taiwan;
| | - Chun-Jung Chen
- Life Science Group, Scientific Research Division, National Synchrotron Radiation Research Center, Hsinchu 33076, Taiwan;
- Department of Biotechnology and Bioindustry Sciences, National Cheng Kung University, Tainan City 701, Taiwan
- Department of Physics, National Tsing Hua University, Hsinchu 30043, Taiwan
- Department of Biological Science and Technology, National Chiao Tung University, Hsinchu 300193, Taiwan
- Correspondence: (C.-J.C.); (C.-Y.H.)
| | - Cheng-Yang Huang
- School of Biomedical Sciences, Chung Shan Medical University, No.110, Sec.1, Chien-Kuo N. Rd., Taichung City 402, Taiwan;
- Department of Medical Research, Chung Shan Medical University Hospital, No.110, Sec.1, Chien-Kuo N. Rd., Taichung City 402, Taiwan
- Correspondence: (C.-J.C.); (C.-Y.H.)
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Mechanisms of feedback inhibition and sequential firing of active sites in plant aspartate transcarbamoylase. Nat Commun 2021; 12:947. [PMID: 33574254 PMCID: PMC7878868 DOI: 10.1038/s41467-021-21165-9] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2020] [Accepted: 12/23/2020] [Indexed: 11/09/2022] Open
Abstract
Aspartate transcarbamoylase (ATC), an essential enzyme for de novo pyrimidine biosynthesis, is uniquely regulated in plants by feedback inhibition of uridine 5-monophosphate (UMP). Despite its importance in plant growth, the structure of this UMP-controlled ATC and the regulatory mechanism remain unknown. Here, we report the crystal structures of Arabidopsis ATC trimer free and bound to UMP, complexed to a transition-state analog or bearing a mutation that turns the enzyme insensitive to UMP. We found that UMP binds and blocks the ATC active site, directly competing with the binding of the substrates. We also prove that UMP recognition relies on a loop exclusively conserved in plants that is also responsible for the sequential firing of the active sites. In this work, we describe unique regulatory and catalytic properties of plant ATCs that could be exploited to modulate de novo pyrimidine synthesis and plant growth.
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Biochemical and Genetic Analysis of 4-Hydroxypyridine Catabolism in Arthrobacter sp. Strain IN13. Microorganisms 2020; 8:microorganisms8060888. [PMID: 32545463 PMCID: PMC7356986 DOI: 10.3390/microorganisms8060888] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2020] [Revised: 06/09/2020] [Accepted: 06/10/2020] [Indexed: 11/16/2022] Open
Abstract
N-Heterocyclic compounds are widely spread in the biosphere, being constituents of alkaloids, cofactors, allelochemicals, and artificial substances. However, the fate of such compounds including a catabolism of hydroxylated pyridines is not yet fully understood. Arthrobacter sp. IN13 is capable of using 4-hydroxypyridine as a sole source of carbon and energy. Three substrate-inducible proteins were detected by comparing protein expression profiles, and peptide mass fingerprinting was performed using MS/MS. After partial sequencing of the genome, we were able to locate genes encoding 4-hydroxypyridine-inducible proteins and identify the kpi gene cluster consisting of 16 open reading frames. The recombinant expression of genes from this locus in Escherichia coli and Rhodococcus erytropolis SQ1 allowed an elucidation of the biochemical functions of the proteins. We report that in Arthrobacter sp. IN13, the initial hydroxylation of 4-hydroxypyridine is catalyzed by a flavin-dependent monooxygenase (KpiA). A product of the monooxygenase reaction is identified as 3,4-dihydroxypyridine, and a subsequent oxidative opening of the ring is performed by a hypothetical amidohydrolase (KpiC). The 3-(N-formyl)-formiminopyruvate formed in this reaction is further converted by KpiB hydrolase to 3-formylpyruvate. Thus, the degradation of 4-hydroxypyridine in Arthrobacter sp. IN13 was analyzed at genetic and biochemical levels, elucidating this catabolic pathway.
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Lipowska J, Miks CD, Kwon K, Shuvalova L, Zheng H, Lewiński K, Cooper DR, Shabalin IG, Minor W. Pyrimidine biosynthesis in pathogens - Structures and analysis of dihydroorotases from Yersinia pestis and Vibrio cholerae. Int J Biol Macromol 2019; 136:1176-1187. [PMID: 31207330 PMCID: PMC6686667 DOI: 10.1016/j.ijbiomac.2019.05.149] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2019] [Revised: 05/01/2019] [Accepted: 05/14/2019] [Indexed: 02/06/2023]
Abstract
The de novo pyrimidine biosynthesis pathway is essential for the proliferation of many pathogens. One of the pathway enzymes, dihydroorotase (DHO), catalyzes the reversible interconversion of N-carbamoyl-l-aspartate to 4,5-dihydroorotate. The substantial difference between bacterial and mammalian DHOs makes it a promising drug target for disrupting bacterial growth and thus an important candidate to evaluate as a response to antimicrobial resistance on a molecular level. Here, we present two novel three-dimensional structures of DHOs from Yersinia pestis (YpDHO), the plague-causing pathogen, and Vibrio cholerae (VcDHO), the causative agent of cholera. The evaluations of these two structures led to an analysis of all available DHO structures and their classification into known DHO types. Comparison of all the DHO active sites containing ligands that are listed in DrugBank was facilitated by a new interactive, structure-comparison and presentation platform. In addition, we examined the genetic context of characterized DHOs, which revealed characteristic patterns for different types of DHOs. We also generated a homology model for DHO from Plasmodium falciparum.
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Affiliation(s)
- Joanna Lipowska
- Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, VA 22908, USA; Center for Structural Genomics of Infectious Diseases (CSGID), Charlottesville, VA 22908, USA; Faculty of Chemistry, Jagiellonian University, 30-387 Kraków, Poland
| | - Charles Dylan Miks
- Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, VA 22908, USA
| | - Keehwan Kwon
- Infectious Diseases Group, J. Craig Venter Institute, Rockville, MD 20850, USA
| | - Ludmilla Shuvalova
- Center for Structural Genomics of Infectious Diseases (CSGID), Chicago, IL 60611, USA
| | - Heping Zheng
- Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, VA 22908, USA; Center for Structural Genomics of Infectious Diseases (CSGID), Charlottesville, VA 22908, USA
| | | | - David R Cooper
- Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, VA 22908, USA; Center for Structural Genomics of Infectious Diseases (CSGID), Charlottesville, VA 22908, USA
| | - Ivan G Shabalin
- Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, VA 22908, USA; Center for Structural Genomics of Infectious Diseases (CSGID), Charlottesville, VA 22908, USA.
| | - Wladek Minor
- Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, VA 22908, USA; Center for Structural Genomics of Infectious Diseases (CSGID), Charlottesville, VA 22908, USA.
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Abstract
The gene that codes for the putative dihydroorotase in the hyperthermophilic archaeon Methanococcus jannaschii was subcloned in pET-21a and expressed in Escherichia coli. A purification protocol was devised. The purity of the protein was evaluated by SDS-PAGE and the protein was confirmed by sequencing using LC-MS. The calculated molecular mass is 48104 Da. SEC-LS suggested that the protein is a monomer in solution. ICP-MS showed that there are two Zn ions per monomer. Kinetic analysis of the recombinant protein gave hyperbolic kinetics with Vmax = 12.2 µmol/min/mg and Km = 0.14 mM at 25 °C. Furthermore the activity of the protein increased with temperature consistent with the hyperthermophilic nature of the organism. A homology model was constructed using the mesophilic Bacillus anthracis protein as the template. Residues known to be critical for Zn and substrate binding were conserved. The activity of the enzyme at 85 and 90 °C was found to be relatively constant over 160 min and this correlates with the temperature of optimal growth of the organism of 85 °C. The amino acid sequences and structures of the two proteins were compared and this gave insight into some of the factors that may confer thermostability-more Lys and Ile, fewer Ala, Thr, Gln and Gly residues, and shorter N- and C-termini. Additional and better insight into the thermostabilization strategies adopted by this enzyme will be provided when its crystal structure is determined.
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Affiliation(s)
- Jacqueline Vitali
- Department of Physics, Cleveland State University, Cleveland, OH, 44115, USA.
- Department of Biology, Geology and Environmental Sciences, Cleveland State University, Cleveland, OH, 44115, USA.
| | - Aditya K Singh
- Department of Physics, Cleveland State University, Cleveland, OH, 44115, USA
- Department of Pharmacology and Toxicology, University of Texas Medical Branch, Galveston, TX, 77555, USA
| | - Michael J Colaneri
- Department of Chemistry and Physics, State University of New York at Old Westbury, Old Westbury, NY, 11568, USA
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Hervé G, Evans HG, Fernado R, Patel C, Hachem F, Evans DR. Activation of Latent Dihydroorotase from Aquifex aeolicus by Pressure. J Biol Chem 2017; 292:629-637. [PMID: 27746403 DOI: 10.1074/jbc.m116.739862] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2016] [Revised: 10/14/2016] [Indexed: 01/12/2023] Open
Abstract
Elevated hydrostatic pressure was used to probe conformational changes of Aquifex aeolicus dihydroorotase (DHO), which catalyzes the third step in de novo pyrimidine biosynthesis. The isolated protein, a 45-kDa monomer, lacks catalytic activity but becomes active upon formation of a dodecameric complex with aspartate transcarbamoylase (ATC). X-ray crystallographic studies of the isolated DHO and of the complex showed that association induces several major conformational changes in the DHO structure. In the isolated DHO, a flexible loop occludes the active site blocking the access of substrates. The loop is mostly disordered but is tethered to the active site region by several electrostatic and hydrogen bonds. This loop becomes ordered and is displaced from the active site upon formation of DHO-ATC complex. The application of pressure to the complex causes its time-dependent dissociation and the loss of both DHO and ATC activities. Pressure induced irreversible dissociation of the obligate ATC trimer, and as a consequence the DHO is also inactivated. However, moderate hydrostatic pressure applied to the isolated DHO subunit mimics the complex formation and reversibly activates the isolated subunit in the absence of ATC, suggesting that the loop has been displaced from the active site. This effect of pressure is explained by the negative volume change associated with the disruption of ionic interactions and exposure of ionized amino acids to the solvent (electrostriction). The interpretation that the loop is relocated by pressure was validated by site-directed mutagenesis and by inhibition by small peptides that mimic the loop residues.
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Affiliation(s)
- Guy Hervé
- From the Laboratoire BIOSIPE, Sorbonne Universités, Institut de Biologie Paris Seine, CNRS, Université Pierre et Marie Curie, 75005 Paris, France,
| | - Hedeel Guy Evans
- the Department of Chemistry, Eastern Michigan University, Ypsilanti, Michigan 48197, and.,the Department of Biochemistry and Molecular Biology, Wayne State University School of Medicine, Detroit, Michigan 48201
| | - Roshini Fernado
- the Department of Chemistry, Eastern Michigan University, Ypsilanti, Michigan 48197, and
| | - Chandni Patel
- the Department of Biochemistry and Molecular Biology, Wayne State University School of Medicine, Detroit, Michigan 48201
| | - Fatme Hachem
- the Department of Biochemistry and Molecular Biology, Wayne State University School of Medicine, Detroit, Michigan 48201
| | - David R Evans
- the Department of Biochemistry and Molecular Biology, Wayne State University School of Medicine, Detroit, Michigan 48201
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Shi D, Allewell NM, Tuchman M. From Genome to Structure and Back Again: A Family Portrait of the Transcarbamylases. Int J Mol Sci 2015; 16:18836-64. [PMID: 26274952 PMCID: PMC4581275 DOI: 10.3390/ijms160818836] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2015] [Revised: 07/29/2015] [Accepted: 07/30/2015] [Indexed: 11/18/2022] Open
Abstract
Enzymes in the transcarbamylase family catalyze the transfer of a carbamyl group from carbamyl phosphate (CP) to an amino group of a second substrate. The two best-characterized members, aspartate transcarbamylase (ATCase) and ornithine transcarbamylase (OTCase), are present in most organisms from bacteria to humans. Recently, structures of four new transcarbamylase members, N-acetyl-l-ornithine transcarbamylase (AOTCase), N-succinyl-l-ornithine transcarbamylase (SOTCase), ygeW encoded transcarbamylase (YTCase) and putrescine transcarbamylase (PTCase) have also been determined. Crystal structures of these enzymes have shown that they have a common overall fold with a trimer as their basic biological unit. The monomer structures share a common CP binding site in their N-terminal domain, but have different second substrate binding sites in their C-terminal domain. The discovery of three new transcarbamylases, l-2,3-diaminopropionate transcarbamylase (DPTCase), l-2,4-diaminobutyrate transcarbamylase (DBTCase) and ureidoglycine transcarbamylase (UGTCase), demonstrates that our knowledge and understanding of the spectrum of the transcarbamylase family is still incomplete. In this review, we summarize studies on the structures and function of transcarbamylases demonstrating how structural information helps to define biological function and how small structural differences govern enzyme specificity. Such information is important for correctly annotating transcarbamylase sequences in the genome databases and for identifying new members of the transcarbamylase family.
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Affiliation(s)
- Dashuang Shi
- Center for Genetic Medicine Research, Children's National Medical Center, the George Washington University, Washington, DC 20010, USA.
- Department of Integrative Systems Biology, Children's National Medical Center, the George Washington University, Washington, DC 20010, USA.
| | - Norma M Allewell
- Department of Cell Biology and Molecular Genetics, College of Computer, Mathematical, and Natural Sciences, University of Maryland, College Park, MD 20742, USA.
- Department of Chemistry and Biochemistry, College of Computer, Mathematical, and Natural Sciences, University of Maryland, College Park, MD 20742, USA.
| | - Mendel Tuchman
- Center for Genetic Medicine Research, Children's National Medical Center, the George Washington University, Washington, DC 20010, USA.
- Department of Integrative Systems Biology, Children's National Medical Center, the George Washington University, Washington, DC 20010, USA.
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Evolutionary expansion of the amidohydrolase superfamily in bacteria in response to the synthetic compounds molinate and diuron. Appl Environ Microbiol 2015; 81:2612-24. [PMID: 25636851 DOI: 10.1128/aem.04016-14] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The amidohydrolase superfamily has remarkable functional diversity, with considerable structural and functional annotation of known sequences. In microbes, the recent evolution of several members of this family to catalyze the breakdown of environmental xenobiotics is not well understood. An evolutionary transition from binuclear to mononuclear metal ion coordination at the active sites of these enzymes could produce large functional changes such as those observed in nature, but there are few clear examples available to support this hypothesis. To investigate the role of binuclear-mononuclear active-site transitions in the evolution of new function in this superfamily, we have characterized two recently evolved enzymes that catalyze the hydrolysis of the synthetic herbicides molinate (MolA) and phenylurea (PuhB). In this work, the crystal structures, mutagenesis, metal ion analysis, and enzyme kinetics of both MolA and PuhB establish that these enzymes utilize a mononuclear active site. However, bioinformatics and structural comparisons reveal that the closest putative ancestor of these enzymes had a binuclear active site, indicating that a binuclear-mononuclear transition has occurred. These proteins may represent examples of evolution modifying the characteristics of existing catalysts to satisfy new requirements, specifically, metal ion rearrangement leading to large leaps in activity that would not otherwise be possible.
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