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Chang J, Yuan W, Gao C, Zhang B, Liu JL, Chen G, Tan YW. Single-Molecule Fluorescence Imaging Reveals Coassembly of CTPS and P5CS. J Phys Chem B 2024; 128:949-959. [PMID: 38236746 DOI: 10.1021/acs.jpcb.3c06498] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2024]
Abstract
The cellular compartmentation induced by self-assembly of natural proteins has recently attracted widespread attention due to its structural-functional significance. Among them, as a highly conserved metabolic enzyme and one of the potential targets for cancers and parasitic diseases in drug development, CTP synthase (CTPS) has also been reported to self-assemble into filamentous structures termed cytoophidia. To elucidate the dynamical mechanism of cytoophidium filamentation, we utilize single-molecule fluorescence imaging to observe the real-time self-assembly dynamics of CTPS and the coordinated assembly between CTPS and its interaction partner, Δ1-pyrroline-5-carboxylate synthase (P5CS). Significant differences exist in the direction of growth and extension when the two proteins self-assemble. The oligomer state distribution analysis of the CTPS minimum structural subunit under different conditions and the stoichiometry statistics of binding CTPS and P5CS by single-molecule fluorescence photobleach counting further confirm that the CTPS cytoophidia are mainly stacked with tetramers. CTPS can act as the nucleation core to induce the subsequent growth of the P5CS filaments. Our work not only provide evidence from the molecular level for the self-assembly and coordinated assembly (coassembly) of CTPS with its interaction partner P5CS in vitro but also offer new experimental perspectives for the dynamics research of coordinated regulation between other protein polymers.
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Affiliation(s)
- Jian Chang
- State Key Laboratory of Surface Physics, Shanghai Key Laboratory of Metasurfaces for Light Manipulation, Department of Physics, Fudan University, Shanghai 200433, China
| | - Weijie Yuan
- State Key Laboratory of Surface Physics, Shanghai Key Laboratory of Metasurfaces for Light Manipulation, Department of Physics, Fudan University, Shanghai 200433, China
| | - Chendi Gao
- The State Key Laboratory of Molecular Engineering of Polymers and Department of Macromolecular Science, Fudan University, Shanghai 200433, China
| | - Bo Zhang
- School of Life Science and Technology, ShanghaiTech University, Shanghai 201210, China
| | - Ji-Long Liu
- School of Life Science and Technology, ShanghaiTech University, Shanghai 201210, China
- MRC Functional Genomics Unit, Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford OX1 3PT, United Kingdom
| | - Guosong Chen
- The State Key Laboratory of Molecular Engineering of Polymers and Department of Macromolecular Science, Fudan University, Shanghai 200433, China
| | - Yan-Wen Tan
- State Key Laboratory of Surface Physics, Shanghai Key Laboratory of Metasurfaces for Light Manipulation, Department of Physics, Fudan University, Shanghai 200433, China
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2
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Gillis TD, Bearne SL. Effects of the 5'-Triphosphate Metabolites of Ribavirin, Sofosbuvir, Vidarabine, and Molnupiravir on CTP Synthase Catalysis and Filament Formation: Implications for Repurposing Antiviral Agents against SARS-CoV-2. ChemMedChem 2022; 17:e202200399. [PMID: 36184568 PMCID: PMC9538051 DOI: 10.1002/cmdc.202200399] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2022] [Revised: 09/22/2022] [Indexed: 01/14/2023]
Abstract
Repurposing of antiviral drugs affords a rapid and effective strategy to develop therapies to counter pandemics such as COVID-19. SARS-CoV-2 replication is closely linked to the metabolism of cytosine-containing nucleotides, especially cytidine-5'-triphosphate (CTP), such that the integrity of the viral genome is highly sensitive to intracellular CTP levels. CTP synthase (CTPS) catalyzes the rate-limiting step for the de novo biosynthesis of CTP. Hence, it is of interest to know the effects of the 5'-triphosphate (TP) metabolites of repurposed antiviral agents on CTPS activity. Using E. coli CTPS as a model enzyme, we show that ribavirin-5'-TP is a weak allosteric activator of CTPS, while sofosbuvir-5'-TP and adenine-arabinofuranoside-5'-TP are both substrates. β-d-N4 -Hydroxycytidine-5'-TP is a weak competitive inhibitor relative to CTP, but induces filament formation by CTPS. Alternatively, sofosbuvir-5'-TP prevented CTP-induced filament formation. These results reveal the underlying potential for repurposed antivirals to affect the activity of a critical pyrimidine nucleotide biosynthetic enzyme.
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Affiliation(s)
- Thomas D. Gillis
- Dalhousie UniversityDepartment of Biochemistry & Molecular Biology5850 College St.Tupper Medical Building, 9JB3H 4R2HalifaxCANADA
| | - Stephen L. Bearne
- Dalhousie UniversityBiochemistry & Molecular Biology5850 College StreetTupper Medical BuildingB3H 4R2HalifaxCANADA
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3
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Dayie TK, Olenginski LT, Taiwo KM. Isotope Labels Combined with Solution NMR Spectroscopy Make Visible the Invisible Conformations of Small-to-Large RNAs. Chem Rev 2022; 122:9357-9394. [PMID: 35442658 PMCID: PMC9136934 DOI: 10.1021/acs.chemrev.1c00845] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2021] [Indexed: 02/07/2023]
Abstract
RNA is central to the proper function of cellular processes important for life on earth and implicated in various medical dysfunctions. Yet, RNA structural biology lags significantly behind that of proteins, limiting mechanistic understanding of RNA chemical biology. Fortunately, solution NMR spectroscopy can probe the structural dynamics of RNA in solution at atomic resolution, opening the door to their functional understanding. However, NMR analysis of RNA, with only four unique ribonucleotide building blocks, suffers from spectral crowding and broad linewidths, especially as RNAs grow in size. One effective strategy to overcome these challenges is to introduce NMR-active stable isotopes into RNA. However, traditional uniform labeling methods introduce scalar and dipolar couplings that complicate the implementation and analysis of NMR measurements. This challenge can be circumvented with selective isotope labeling. In this review, we outline the development of labeling technologies and their application to study biologically relevant RNAs and their complexes ranging in size from 5 to 300 kDa by NMR spectroscopy.
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Affiliation(s)
- Theodore K. Dayie
- Department of Chemistry and Biochemistry, University of Maryland, College Park, Maryland 20742, United States
| | - Lukasz T. Olenginski
- Department of Chemistry and Biochemistry, University of Maryland, College Park, Maryland 20742, United States
| | - Kehinde M. Taiwo
- Department of Chemistry and Biochemistry, University of Maryland, College Park, Maryland 20742, United States
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4
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GTP-Dependent Regulation of CTP Synthase: Evolving Insights into Allosteric Activation and NH3 Translocation. Biomolecules 2022; 12:biom12050647. [PMID: 35625575 PMCID: PMC9138612 DOI: 10.3390/biom12050647] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2022] [Revised: 04/21/2022] [Accepted: 04/21/2022] [Indexed: 12/24/2022] Open
Abstract
Cytidine-5′-triphosphate (CTP) synthase (CTPS) is the class I glutamine-dependent amidotransferase (GAT) that catalyzes the last step in the de novo biosynthesis of CTP. Glutamine hydrolysis is catalyzed in the GAT domain and the liberated ammonia is transferred via an intramolecular tunnel to the synthase domain where the ATP-dependent amination of UTP occurs to form CTP. CTPS is unique among the glutamine-dependent amidotransferases, requiring an allosteric effector (GTP) to activate the GAT domain for efficient glutamine hydrolysis. Recently, the first cryo-electron microscopy structure of Drosophila CTPS was solved with bound ATP, UTP, and, notably, GTP, as well as the covalent adduct with 6-diazo-5-oxo-l-norleucine. This structural information, along with the numerous site-directed mutagenesis, kinetics, and structural studies conducted over the past 50 years, provide more detailed insights into the elaborate conformational changes that accompany GTP binding at the GAT domain and their contribution to catalysis. Interactions between GTP and the L2 loop, the L4 loop from an adjacent protomer, the L11 lid, and the L13 loop (or unique flexible “wing” region), induce conformational changes that promote the hydrolysis of glutamine at the GAT domain; however, direct experimental evidence on the specific mechanism by which these conformational changes facilitate catalysis at the GAT domain is still lacking. Significantly, the conformational changes induced by GTP binding also affect the assembly and maintenance of the NH3 tunnel. Hence, in addition to promoting glutamine hydrolysis, the allosteric effector plays an important role in coordinating the reactions catalyzed by the GAT and synthase domains of CTPS.
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5
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Olenginski LT, Taiwo KM, LeBlanc RM, Dayie TK. Isotope-Labeled RNA Building Blocks for NMR Structure and Dynamics Studies. Molecules 2021; 26:molecules26185581. [PMID: 34577051 PMCID: PMC8466439 DOI: 10.3390/molecules26185581] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2021] [Revised: 09/05/2021] [Accepted: 09/07/2021] [Indexed: 01/19/2023] Open
Abstract
RNA structural research lags behind that of proteins, preventing a robust understanding of RNA functions. NMR spectroscopy is an apt technique for probing the structures and dynamics of RNA molecules in solution at atomic resolution. Still, RNA analysis by NMR suffers from spectral overlap and line broadening, both of which worsen for larger RNAs. Incorporation of stable isotope labels into RNA has provided several solutions to these challenges. In this review, we summarize the benefits and limitations of various methods used to obtain isotope-labeled RNA building blocks and how they are used to prepare isotope-labeled RNA for NMR structure and dynamics studies.
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Affiliation(s)
- Lukasz T. Olenginski
- Center for Biomolecular Structure and Organization, Department of Chemistry and Biochemistry, University of Maryland, College Park, MD 20742, USA; (L.T.O.); (K.M.T.); (R.M.L.)
| | - Kehinde M. Taiwo
- Center for Biomolecular Structure and Organization, Department of Chemistry and Biochemistry, University of Maryland, College Park, MD 20742, USA; (L.T.O.); (K.M.T.); (R.M.L.)
| | - Regan M. LeBlanc
- Center for Biomolecular Structure and Organization, Department of Chemistry and Biochemistry, University of Maryland, College Park, MD 20742, USA; (L.T.O.); (K.M.T.); (R.M.L.)
- Vertex Pharmaceuticals, 50 Northern Avenue, Boston, MA 02210, USA
| | - Theodore K. Dayie
- Center for Biomolecular Structure and Organization, Department of Chemistry and Biochemistry, University of Maryland, College Park, MD 20742, USA; (L.T.O.); (K.M.T.); (R.M.L.)
- Correspondence: ; Tel.: +1-301-405-3165
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6
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Wang Y, Wang G, Moitessier N, Mittermaier AK. Enzyme Kinetics by Isothermal Titration Calorimetry: Allostery, Inhibition, and Dynamics. Front Mol Biosci 2020; 7:583826. [PMID: 33195429 PMCID: PMC7604385 DOI: 10.3389/fmolb.2020.583826] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2020] [Accepted: 09/11/2020] [Indexed: 12/14/2022] Open
Abstract
Isothermal titration calorimetry (ITC) involves accurately measuring the heat that is released or absorbed in real time when one solution is titrated into another. This technique is usually used to measure the thermodynamics of binding reactions. However, there is mounting interest in using it to measure reaction kinetics, particularly enzymatic catalysis. This application of ITC has been steadily growing for the past two decades, and the method is proving to be sensitive, generally applicable, and capable of providing information on enzyme activity that is difficult to obtain using traditional biochemical assays. This review aims to give a broad overview of the use of ITC to measure enzyme kinetics. It describes several different classes of ITC experiment, their strengths and weaknesses, and recent methodological advancements. A summary of applications in the literature is given and several examples where ITC has been used to investigate challenging aspects of enzyme behavior are presented in more detail. These include examples of allostery, where small-molecule binding outside the active site modulates activity. We describe the use of ITC to measure the strength, mode (i.e., competitive, uncompetitive, or mixed), and association and dissociation kinetics of enzyme inhibitors. Further, we provide examples of ITC applied to complex, heterogeneous mixtures, such as insoluble substrates and live cells. These studies exemplify the wide range of problems where ITC can provide answers, and illustrate the versatility of the technique and potential for future development and applications.
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Affiliation(s)
- Yun Wang
- Department of Chemistry, McGill University, Montreal, QC, Canada
| | - Guanyu Wang
- Department of Chemistry, McGill University, Montreal, QC, Canada
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7
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Simonet JC, Foster MJ, Lynch EM, Kollman JM, Nicholas E, O'Reilly AM, Peterson JR. CTP synthase polymerization in germline cells of the developing Drosophila egg supports egg production. Biol Open 2020; 9:bio050328. [PMID: 32580972 PMCID: PMC7390647 DOI: 10.1242/bio.050328] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2019] [Accepted: 06/16/2020] [Indexed: 01/19/2023] Open
Abstract
Polymerization of metabolic enzymes into micron-scale assemblies is an emerging mechanism for regulating their activity. CTP synthase (CTPS) is an essential enzyme in the biosynthesis of the nucleotide CTP and undergoes regulated and reversible assembly into large filamentous structures in organisms from bacteria to humans. The purpose of these assemblies is unclear. A major challenge to addressing this question has been the inability to abolish assembly without eliminating CTPS protein. Here we demonstrate that a recently reported point mutant in CTPS, Histidine 355A (H355A), prevents CTPS filament assembly in vivo and dominantly inhibits the assembly of endogenous wild-type CTPS in the Drosophila ovary. Expressing this mutant in ovarian germline cells, we show that disruption of CTPS assembly in early stage egg chambers reduces egg production. This effect is exacerbated in flies fed the glutamine antagonist 6-diazo-5-oxo-L-norleucine, which inhibits de novo CTP synthesis. These findings introduce a general approach to blocking the assembly of polymerizing enzymes without eliminating their catalytic activity and demonstrate a role for CTPS assembly in supporting egg production, particularly under conditions of limited glutamine metabolism.This article has an associated First Person interview with the first author of the paper.
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Affiliation(s)
- Jacqueline C Simonet
- Cancer Biology Program, Fox Chase Cancer Center, 333 Cottman Avenue, Philadelphia, PA 19111, USA
| | - Maya J Foster
- Immersion Science Program, Fox Chase Cancer Center, 333 Cottman Avenue, Philadelphia, PA 19111, USA
| | - Eric M Lynch
- Department of Biochemistry, University of Washington, Seattle, WA 98195, USA
| | - Justin M Kollman
- Department of Biochemistry, University of Washington, Seattle, WA 98195, USA
| | - Emmanuelle Nicholas
- Cancer Biology Program, Fox Chase Cancer Center, 333 Cottman Avenue, Philadelphia, PA 19111, USA
| | - Alana M O'Reilly
- Molecular Therapeutics Program, Fox Chase Cancer Center, 333 Cottman Avenue, Philadelphia, PA 19111, USA
| | - Jeffrey R Peterson
- Cancer Biology Program, Fox Chase Cancer Center, 333 Cottman Avenue, Philadelphia, PA 19111, USA
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8
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Daumann M, Hickl D, Zimmer D, DeTar RA, Kunz HH, Möhlmann T. Characterization of filament-forming CTP synthases from Arabidopsis thaliana. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2018; 96:316-328. [PMID: 30030857 PMCID: PMC6821390 DOI: 10.1111/tpj.14032] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/17/2017] [Revised: 05/14/2018] [Accepted: 05/22/2018] [Indexed: 05/27/2023]
Abstract
Cytidine triphosphate (CTP) is essential for DNA, RNA and phospholipid biosynthesis. De novo synthesis is catalyzed by CTP synthases (CTPS). Arabidopsis encodes five CTPS isoforms that unanimously share conserved motifs found across kingdoms, suggesting all five are functional enzymes. Whereas CTPS1-4 are expressed throughout Arabidopsis tissues, CTPS5 reveals exclusive expression in developing embryos. CTPS activity and substrates affinities were determined for a representative plant enzyme on purified recombinant CTPS3 protein. As demonstrated in model organisms such as yeast, fruit fly and mammals, CTPS show the capacity to assemble into large filaments called cytoophidia. Transient expression of N- and C-terminal YFP-CTPS fusion proteins in Nicotiana benthamiana allowed to monitor such filament formation. Interestingly, CTPS1 and 2 always appeared as soluble proteins, whereas filaments were observed for CTPS3, 4 and 5 independent of the YFP-tag location. However, when similar constructs were expressed in Saccharomyces cerevisiae, no filaments were observed, pointing to a requirement for organism-specific factors in vivo. Indications for filament assembly were also obtained in vitro when recombinant CTPS3 protein was incubated in the presence of CTP. T-DNA-insertion mutants in four CTPS loci revealed no apparent phenotypical alteration. In contrast, CTPS2 T-DNA-insertion mutants did not produce homozygous progenies. An initial characterization of the CTPS protein family members from Arabidopsis is presented. We provide evidence for their involvement in nucleotide de novo synthesis and show that only three of the five CTPS isoforms were able to form filamentous structures in the transient tobacco expression system. This represents a striking difference from previous observations in prokaryotes, yeast, Drosophila and mammalian cells. This finding will be highly valuable to further understand the role of filament formation to regulate CTPS activity.
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Affiliation(s)
- Manuel Daumann
- Pflanzenphysiologie, Fachbereich Biologie, Universität Kaiserslautern, Erwin-Schrodinger-Straße, D-67663, Kaiserslautern, Germany, and
| | - Daniel Hickl
- Pflanzenphysiologie, Fachbereich Biologie, Universität Kaiserslautern, Erwin-Schrodinger-Straße, D-67663, Kaiserslautern, Germany, and
| | - David Zimmer
- Pflanzenphysiologie, Fachbereich Biologie, Universität Kaiserslautern, Erwin-Schrodinger-Straße, D-67663, Kaiserslautern, Germany, and
| | - Rachael A. DeTar
- School of Biological Sciences, Washington State University, PO Box 644236, Pullman, WA, 99164-4236, USA
| | - Hans-Henning Kunz
- School of Biological Sciences, Washington State University, PO Box 644236, Pullman, WA, 99164-4236, USA
| | - Torsten Möhlmann
- Pflanzenphysiologie, Fachbereich Biologie, Universität Kaiserslautern, Erwin-Schrodinger-Straße, D-67663, Kaiserslautern, Germany, and
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9
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Esposito M, Szadocka S, Degiacomi G, Orena BS, Mori G, Piano V, Boldrin F, Zemanová J, Huszár S, Barros D, Ekins S, Lelièvre J, Manganelli R, Mattevi A, Pasca MR, Riccardi G, Ballell L, Mikušová K, Chiarelli LR. A Phenotypic Based Target Screening Approach Delivers New Antitubercular CTP Synthetase Inhibitors. ACS Infect Dis 2017; 3:428-437. [PMID: 28475832 DOI: 10.1021/acsinfecdis.7b00006] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Despite its great potential, the target-based approach has been mostly unsuccessful in tuberculosis drug discovery, while whole cell phenotypic screening has delivered several active compounds. However, for many of these hits, the cellular target has not yet been identified, thus preventing further target-based optimization of the compounds. In this context, the newly validated drug target CTP synthetase PyrG was exploited to assess a target-based approach of already known, but untargeted, antimycobacterial compounds. To this purpose the publically available GlaxoSmithKline antimycobacterial compound set was assayed, uncovering a series of 4-(pyridin-2-yl)thiazole derivatives which efficiently inhibit the Mycobacterium tuberculosis PyrG enzyme activity, one of them showing low activity against the human CTP synthetase. The three best compounds were ATP binding site competitive inhibitors, with Ki values ranging from 3 to 20 μM, but did not show any activity against a small panel of different prokaryotic and eukaryotic kinases, thus demonstrating specificity for the CTP synthetases. Metabolic labeling experiments demonstrated that the compounds directly interfere not only with CTP biosynthesis, but also with other CTP dependent biochemical pathways, such as lipid biosynthesis. Moreover, using a M. tuberculosis pyrG conditional knock-down strain, it was shown that the activity of two compounds is dependent on the intracellular concentration of the CTP synthetase. All these results strongly suggest a role of PyrG as a target of these compounds, thus strengthening the value of this kind of approach for the identification of new scaffolds for drug development.
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Affiliation(s)
- Marta Esposito
- Department
of Biology and Biotechnology “Lazzaro Spallanzani”, University of Pavia, via Ferrata 9, 27100 Pavia, Italy
| | - Sára Szadocka
- Department
of Biochemistry, Faculty of Natural Sciences, Comenius University in Bratislava, Mlynská dolina CH1, 84215 Bratislava, Slovakia
| | - Giulia Degiacomi
- Department
of Molecular Medicine, University of Padova, via Gabelli 63, 35121 Padova, Italy
| | - Beatrice S. Orena
- Department
of Biology and Biotechnology “Lazzaro Spallanzani”, University of Pavia, via Ferrata 9, 27100 Pavia, Italy
| | - Giorgia Mori
- Department
of Biology and Biotechnology “Lazzaro Spallanzani”, University of Pavia, via Ferrata 9, 27100 Pavia, Italy
| | - Valentina Piano
- Department
of Biology and Biotechnology “Lazzaro Spallanzani”, University of Pavia, via Ferrata 9, 27100 Pavia, Italy
| | - Francesca Boldrin
- Department
of Molecular Medicine, University of Padova, via Gabelli 63, 35121 Padova, Italy
| | - Júlia Zemanová
- Department
of Biochemistry, Faculty of Natural Sciences, Comenius University in Bratislava, Mlynská dolina CH1, 84215 Bratislava, Slovakia
| | - Stanislav Huszár
- Department
of Biochemistry, Faculty of Natural Sciences, Comenius University in Bratislava, Mlynská dolina CH1, 84215 Bratislava, Slovakia
| | - David Barros
- Diseases
of the Developing World, GlaxoSmithKline, Calle Severo Ochoa 2, 28760 Tres Cantos, Madrid, Spain
| | - Sean Ekins
- Collaborative Drug Discovery Inc., 1633 Bayshore Highway, Suite 342, Burlingame, California 94010, United States
| | - Joel Lelièvre
- Diseases
of the Developing World, GlaxoSmithKline, Calle Severo Ochoa 2, 28760 Tres Cantos, Madrid, Spain
| | - Riccardo Manganelli
- Department
of Molecular Medicine, University of Padova, via Gabelli 63, 35121 Padova, Italy
| | - Andrea Mattevi
- Department
of Biology and Biotechnology “Lazzaro Spallanzani”, University of Pavia, via Ferrata 9, 27100 Pavia, Italy
| | - Maria Rosalia Pasca
- Department
of Biology and Biotechnology “Lazzaro Spallanzani”, University of Pavia, via Ferrata 9, 27100 Pavia, Italy
| | - Giovanna Riccardi
- Department
of Biology and Biotechnology “Lazzaro Spallanzani”, University of Pavia, via Ferrata 9, 27100 Pavia, Italy
| | - Lluis Ballell
- Diseases
of the Developing World, GlaxoSmithKline, Calle Severo Ochoa 2, 28760 Tres Cantos, Madrid, Spain
| | - Katarína Mikušová
- Department
of Biochemistry, Faculty of Natural Sciences, Comenius University in Bratislava, Mlynská dolina CH1, 84215 Bratislava, Slovakia
| | - Laurent R. Chiarelli
- Department
of Biology and Biotechnology “Lazzaro Spallanzani”, University of Pavia, via Ferrata 9, 27100 Pavia, Italy
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10
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McCluskey GD, Mohamady S, Taylor SD, Bearne SL. Exploring the Potent Inhibition of CTP Synthase by Gemcitabine-5'-Triphosphate. Chembiochem 2016; 17:2240-2249. [PMID: 27643605 DOI: 10.1002/cbic.201600405] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2016] [Indexed: 11/10/2022]
Abstract
CTP synthase (CTPS) catalyzes the conversion of UTP to CTP and is a target for the development of antiviral, anticancer, antiprotozoal, and immunosuppressive agents. Exposure of cell lines to the antineoplastic cytidine analogue gemcitabine causes depletion of intracellular CTP levels, but the direct inhibition of CTPS by its metabolite gemcitabine-5'-triphosphate (dF-dCTP) has not been demonstrated. We show that dF-dCTP is a potent competitive inhibitor of Escherichia coli CTPS with respect to UTP [Ki =(3.0±0.1) μm], and that its binding affinity exceeds that of CTP ≈75-fold. Site-directed mutagenesis studies indicated that Glu149 is an important binding determinant for both CTP and dF-dCTP. Comparison of the binding affinities of the 5'-triphosphates of 2'-fluoro-2'-deoxycytidine and 2'-fluoro-2'-deoxyarabinocytidine revealed that the 2'-F-arabino group contributes markedly to the strong binding of dF-dCTP. Geminal 2'-F substitution on UTP (dF-dUTP) did not result in an increase in binding affinity with CTPS. Remarkably, CTPS catalyzed the conversion of dF-dUTP into dF-dCTP, thus suggesting that dF-dCTP might be regenerated in vivo from its catabolite dF-dUTP.
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Affiliation(s)
- Gregory D McCluskey
- Department of Biochemistry and Molecular Biology, Dalhousie University, Halifax, Nova Scotia, B3H 4R2, Canada
| | - Samy Mohamady
- Faculty of Pharmacy, The British University in Egypt, 11837, Cairo, Egypt
| | - Scott D Taylor
- Department of Chemistry, University of Waterloo, Waterloo, Ontario, N2L 3G1, Canada
| | - Stephen L Bearne
- Department of Biochemistry and Molecular Biology, Dalhousie University, Halifax, Nova Scotia, B3H 4R2, Canada.,Department of Chemistry, Dalhousie University, Halifax, Nova Scotia, B3H 4R2, Canada
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11
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Habrian C, Chandrasekhara A, Shahrvini B, Hua B, Lee J, Jesinghaus R, Barry R, Gitai Z, Kollman J, Baldwin EP. Inhibition of Escherichia coli CTP Synthetase by NADH and Other Nicotinamides and Their Mutual Interactions with CTP and GTP. Biochemistry 2016; 55:5554-5565. [PMID: 27571563 DOI: 10.1021/acs.biochem.6b00383] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
CTP synthetases catalyze the last step of pyrimidine biosynthesis and provide the sole de novo source of cytosine-containing nucleotides. As a central regulatory hub, they are regulated by ribonucleotide and enzyme concentration through ATP and UTP substrate availability, CTP product inhibition, GTP allosteric modification, and quaternary structural changes including the formation of CTP-inhibited linear polymers (filaments). Here, we demonstrate that nicotinamide redox cofactors are moderate inhibitors of Escherichia coli CTP synthetase (EcCTPS). NADH and NADPH are the most potent, and the primary inhibitory determinant is the reduced nicotinamide ring. Although nicotinamide inhibition is noncompetitive with substrates, it apparently enhances CTP product feedback inhibition and GTP allosteric regulation. Further, CTP and GTP also enhance each other's effects, consistent with the idea that NADH, CTP, and GTP interact with a common intermediate enzyme state. A filament-blocking mutation that reduces CTP inhibitory effects also reduced inhibition by GTP but not NADH. Protein-concentration effects on GTP inhibition suggest that, like CTP, GTP preferentially binds to the filament. All three compounds display nearly linear dose-dependent inhibition, indicating a complex pattern of cooperative interactions between binding sites. The apparent synergy between inhibitors, in consideration with physiological nucleotide concentrations, points to metabolically relevant inhibition by nicotinamides, and implicates cellular redox state as a regulator of pyrimidine biosynthesis.
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Affiliation(s)
- Chris Habrian
- Department of Molecular and Cellular Biology, University of California, Davis , Davis, California 95616, United States.,Biophysics Graduate Program, University of California, Berkeley , Berkeley, California 94720, United States
| | - Adithi Chandrasekhara
- Department of Molecular and Cellular Biology, University of California, Davis , Davis, California 95616, United States.,Process Development Rotation Program, Genentech Inc. , 1 DNA Way, South San Francisco, California 94080, United States
| | - Bita Shahrvini
- Department of Molecular and Cellular Biology, University of California, Davis , Davis, California 95616, United States
| | - Brian Hua
- Department of Molecular and Cellular Biology, University of California, Davis , Davis, California 95616, United States.,Department of Biology, Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States
| | - Jason Lee
- Department of Molecular and Cellular Biology, University of California, Davis , Davis, California 95616, United States.,Drexel University College of Medicine , Philadelphia, Pennsylvania 19129, United States.,Kaiser Permanente , Sacramento, California 95823, United States
| | - Roger Jesinghaus
- Department of Molecular and Cellular Biology, University of California, Davis , Davis, California 95616, United States
| | - Rachael Barry
- Department of Molecular Biology, Princeton University , Princeton, New Jersey 08544, United States.,Department of Cellular and Molecular Medicine, University of California, San Diego , La Jolla, California 92903, United States
| | - Zemer Gitai
- Department of Molecular Biology, Princeton University , Princeton, New Jersey 08544, United States
| | - Justin Kollman
- Department of Biochemistry, University of Washington , Seattle, Washington 98195, United States
| | - Enoch P Baldwin
- Department of Molecular and Cellular Biology, University of California, Davis , Davis, California 95616, United States
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12
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Abstract
We review literature on the metabolism of ribo- and deoxyribonucleotides, nucleosides, and nucleobases in Escherichia coli and Salmonella,including biosynthesis, degradation, interconversion, and transport. Emphasis is placed on enzymology and regulation of the pathways, at both the level of gene expression and the control of enzyme activity. The paper begins with an overview of the reactions that form and break the N-glycosyl bond, which binds the nucleobase to the ribosyl moiety in nucleotides and nucleosides, and the enzymes involved in the interconversion of the different phosphorylated states of the nucleotides. Next, the de novo pathways for purine and pyrimidine nucleotide biosynthesis are discussed in detail.Finally, the conversion of nucleosides and nucleobases to nucleotides, i.e.,the salvage reactions, are described. The formation of deoxyribonucleotides is discussed, with emphasis on ribonucleotidereductase and pathways involved in fomation of dUMP. At the end, we discuss transport systems for nucleosides and nucleobases and also pathways for breakdown of the nucleobases.
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13
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Mori G, Chiarelli LR, Esposito M, Makarov V, Bellinzoni M, Hartkoorn RC, Degiacomi G, Boldrin F, Ekins S, de Jesus Lopes Ribeiro AL, Marino LB, Centárová I, Svetlíková Z, Blaško J, Kazakova E, Lepioshkin A, Barilone N, Zanoni G, Porta A, Fondi M, Fani R, Baulard AR, Mikušová K, Alzari PM, Manganelli R, de Carvalho LPS, Riccardi G, Cole ST, Pasca MR. Thiophenecarboxamide Derivatives Activated by EthA Kill Mycobacterium tuberculosis by Inhibiting the CTP Synthetase PyrG. ACTA ACUST UNITED AC 2015; 22:917-27. [PMID: 26097035 PMCID: PMC4521081 DOI: 10.1016/j.chembiol.2015.05.016] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2015] [Revised: 05/25/2015] [Accepted: 05/30/2015] [Indexed: 11/06/2022]
Abstract
To combat the emergence of drug-resistant strains of Mycobacterium tuberculosis, new antitubercular agents and novel drug targets are needed. Phenotypic screening of a library of 594 hit compounds uncovered two leads that were active against M. tuberculosis in its replicating, non-replicating, and intracellular states: compounds 7947882 (5-methyl-N-(4-nitrophenyl)thiophene-2-carboxamide) and 7904688 (3-phenyl-N-[(4-piperidin-1-ylphenyl)carbamothioyl]propanamide). Mutants resistant to both compounds harbored mutations in ethA (rv3854c), the gene encoding the monooxygenase EthA, and/or in pyrG (rv1699) coding for the CTP synthetase, PyrG. Biochemical investigations demonstrated that EthA is responsible for the activation of the compounds, and by mass spectrometry we identified the active metabolite of 7947882, which directly inhibits PyrG activity. Metabolomic studies revealed that pharmacological inhibition of PyrG strongly perturbs DNA and RNA biosynthesis, and other metabolic processes requiring nucleotides. Finally, the crystal structure of PyrG was solved, paving the way for rational drug design with this newly validated drug target. Two compounds activated by EthA kill M. tuberculosis through PyrG inhibition EthA metabolite is active against PyrG and M. tuberculosis growth Definition of the mechanism of activation and validation of PyrG as a new drug target
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Affiliation(s)
- Giorgia Mori
- Department of Biology and Biotechnology "Lazzaro Spallanzani", University of Pavia, 27100 Pavia, Italy
| | - Laurent R Chiarelli
- Department of Biology and Biotechnology "Lazzaro Spallanzani", University of Pavia, 27100 Pavia, Italy
| | - Marta Esposito
- Department of Biology and Biotechnology "Lazzaro Spallanzani", University of Pavia, 27100 Pavia, Italy
| | - Vadim Makarov
- A. N. Bakh Institute of Biochemistry, Russian Academy of Science, 119071 Moscow, Russia
| | - Marco Bellinzoni
- Institut Pasteur, Unité de Microbiologie Structurale, CNRS-UMR3528, Université Paris Diderot, Sorbonne Paris Cité, 25 rue du Dr. Roux, 75724 Paris Cedex 15, France
| | - Ruben C Hartkoorn
- Global Health Institute, Ecole Polytechnique Fédérale de Lausanne, Station 19, 1015 Lausanne, Switzerland
| | - Giulia Degiacomi
- Department of Molecular Medicine, University of Padova, 35128 Padua, Italy
| | - Francesca Boldrin
- Department of Molecular Medicine, University of Padova, 35128 Padua, Italy
| | - Sean Ekins
- Collaborative Drug Discovery, 1633 Bayshore Highway, Suite 342, Burlingame, CA 94010, USA
| | | | - Leonardo B Marino
- Francis Crick Institute, Mill Hill Laboratory, The Ridgeway, Mill Hill, London NW7 1AA, UK; Faculty of Pharmaceutical Sciences, UNESP - Univ Estadual Paulista, Araraquara, São Paulo 14801-902, Brazil
| | - Ivana Centárová
- Department of Biochemistry, Faculty of Natural Sciences, Comenius University in Bratislava, Ilkovičova 6, Mlynská dolina, 84215 Bratislava, Slovakia
| | - Zuzana Svetlíková
- Department of Biochemistry, Faculty of Natural Sciences, Comenius University in Bratislava, Ilkovičova 6, Mlynská dolina, 84215 Bratislava, Slovakia
| | - Jaroslav Blaško
- Institute of Chemistry, Faculty of Natural Sciences, Comenius University in Bratislava, Ilkovičova 6, Mlynská dolina, 84215 Bratislava, Slovak Republic
| | - Elena Kazakova
- A. N. Bakh Institute of Biochemistry, Russian Academy of Science, 119071 Moscow, Russia
| | - Alexander Lepioshkin
- A. N. Bakh Institute of Biochemistry, Russian Academy of Science, 119071 Moscow, Russia
| | - Nathalie Barilone
- Institut Pasteur, Unité de Microbiologie Structurale, CNRS-UMR3528, Université Paris Diderot, Sorbonne Paris Cité, 25 rue du Dr. Roux, 75724 Paris Cedex 15, France
| | - Giuseppe Zanoni
- Department of Chemistry, University of Pavia, 27100 Pavia, Italy
| | - Alessio Porta
- Department of Chemistry, University of Pavia, 27100 Pavia, Italy
| | - Marco Fondi
- Department of Biology, University of Florence, Sesto Fiorentino, Florence 50019, Italy
| | - Renato Fani
- Department of Biology, University of Florence, Sesto Fiorentino, Florence 50019, Italy
| | - Alain R Baulard
- Institut Pasteur de Lille, Center for Infection and Immunity, 59019 Lille, France
| | - Katarína Mikušová
- Department of Biochemistry, Faculty of Natural Sciences, Comenius University in Bratislava, Ilkovičova 6, Mlynská dolina, 84215 Bratislava, Slovakia
| | - Pedro M Alzari
- Institut Pasteur, Unité de Microbiologie Structurale, CNRS-UMR3528, Université Paris Diderot, Sorbonne Paris Cité, 25 rue du Dr. Roux, 75724 Paris Cedex 15, France
| | | | | | - Giovanna Riccardi
- Department of Biology and Biotechnology "Lazzaro Spallanzani", University of Pavia, 27100 Pavia, Italy
| | - Stewart T Cole
- Global Health Institute, Ecole Polytechnique Fédérale de Lausanne, Station 19, 1015 Lausanne, Switzerland.
| | - Maria Rosalia Pasca
- Department of Biology and Biotechnology "Lazzaro Spallanzani", University of Pavia, 27100 Pavia, Italy.
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14
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Alvarado LJ, LeBlanc RM, Longhini AP, Keane SC, Jain N, Yildiz ZF, Tolbert BS, D'Souza VM, Summers MF, Kreutz C, Dayie TK. Regio-selective chemical-enzymatic synthesis of pyrimidine nucleotides facilitates RNA structure and dynamics studies. Chembiochem 2014; 15:1573-7. [PMID: 24954297 DOI: 10.1002/cbic.201402130] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2014] [Indexed: 12/16/2022]
Abstract
Isotope labeling has revolutionized NMR studies of small nucleic acids, but to extend this technology to larger RNAs, site-specific labeling tools to expedite NMR structural and dynamics studies are required. Using enzymes from the pentose phosphate pathway, we coupled chemically synthesized uracil nucleobase with specifically (13) C-labeled ribose to synthesize both UTP and CTP in nearly quantitative yields. This chemoenzymatic method affords a cost-effective preparation of labels that are unattainable by current methods. The methodology generates versatile (13) C and (15) N labeling patterns which, when employed with relaxation-optimized NMR spectroscopy, effectively mitigate problems of rapid relaxation that result in low resolution and sensitivity. The methodology is demonstrated with RNAs of various sizes, complexity, and function: the exon splicing silencer 3 (27 nt), iron responsive element (29 nt), Pro-tRNA (76 nt), and HIV-1 core encapsidation signal (155 nt).
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Affiliation(s)
- Luigi J Alvarado
- Center for Biomolecular Structure and Organization, Department of Chemistry and Biochemistry, University of Maryland, 1115 Biomolecular Sciences Building, College Park, MD 20782 (USA)
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15
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Zhu M, Sun W, Wang Y, Meng J, Zhang D, Guo T, Ouyang P, Ying H, Xie J. Engineered cytidine triphosphate synthetase with reduced product inhibition. Protein Eng Des Sel 2014; 27:225-33. [PMID: 24902851 DOI: 10.1093/protein/gzu019] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Cytidine triphosphate (CTP) synthetase (CTPS) (EC number 6.3.4.2) is a key enzyme involved in de novo synthesis of CTP. It catalyzes the rate-limiting step of the process due to the product inhibition effects on the enzyme. In this study, a novel CTPS from Corynebacterium glutamicum ATCC 13032 (CgCTPS) was cloned, expressed and characterized. A series of mutagenesis in its N-terminal ammonia ligase (ALase) domain was performed in order to reduce CTP product inhibition. All single mutation variants (D160E, E162A, E168K) lowered product inhibition by lowering the enzyme's binding affinity for CTP. The homology model of CgCTPS showed that D160E mutant caused steric hindrance for the pyrimidine ring of CTP stacking, E162A disrupted the hydrogen bond between CTP ribose and side chain and D168K caused minor localized structure perturbations of CTP binding pocket. The triple mutant of CTPS (D160E-E162A-E168K) with halved Km, doubled Vmax and the 23.5-fold increased IC50 for CTP shows a potential for use in industrial-scale CTP production by its better performance in enzyme kinetics and product inhibition.
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Affiliation(s)
- Mengzhu Zhu
- State Key Laboratory of Materials-Oriented Chemical Engineering, Nanjing Tech University, Nanjing 211816, People's Republic of China College of Biotechnology and Pharmaceutical Engineering, Nanjing Tech University, Nanjing 211816, People's Republic of China National Engineering Technique Research Center for Biotechnology, Nanjing Tech University, Nanjing 211816, People's Republic of China
| | - Wujin Sun
- Joint Department of Biomedical Engineering, The University of North Carolina at Chapel Hill and North Carolina State University, Raleigh 27695, USA
| | - Yan Wang
- State Key Laboratory of Materials-Oriented Chemical Engineering, Nanjing Tech University, Nanjing 211816, People's Republic of China College of Biotechnology and Pharmaceutical Engineering, Nanjing Tech University, Nanjing 211816, People's Republic of China National Engineering Technique Research Center for Biotechnology, Nanjing Tech University, Nanjing 211816, People's Republic of China
| | - Jie Meng
- State Key Laboratory of Materials-Oriented Chemical Engineering, Nanjing Tech University, Nanjing 211816, People's Republic of China College of Biotechnology and Pharmaceutical Engineering, Nanjing Tech University, Nanjing 211816, People's Republic of China National Engineering Technique Research Center for Biotechnology, Nanjing Tech University, Nanjing 211816, People's Republic of China
| | - Dalu Zhang
- International Cooperation Division, China National Center for Biotechnology Development, Beijing 100036, People's Republic of China
| | - Ting Guo
- State Key Laboratory of Materials-Oriented Chemical Engineering, Nanjing Tech University, Nanjing 211816, People's Republic of China National Engineering Technique Research Center for Biotechnology, Nanjing Tech University, Nanjing 211816, People's Republic of China Guangzhou Sugarcane Industry Research Institute, Guangzhou 510316, People's Republic of China
| | - Pingkai Ouyang
- State Key Laboratory of Materials-Oriented Chemical Engineering, Nanjing Tech University, Nanjing 211816, People's Republic of China College of Biotechnology and Pharmaceutical Engineering, Nanjing Tech University, Nanjing 211816, People's Republic of China National Engineering Technique Research Center for Biotechnology, Nanjing Tech University, Nanjing 211816, People's Republic of China
| | - Hanjie Ying
- State Key Laboratory of Materials-Oriented Chemical Engineering, Nanjing Tech University, Nanjing 211816, People's Republic of China College of Biotechnology and Pharmaceutical Engineering, Nanjing Tech University, Nanjing 211816, People's Republic of China National Engineering Technique Research Center for Biotechnology, Nanjing Tech University, Nanjing 211816, People's Republic of China
| | - Jingjing Xie
- State Key Laboratory of Materials-Oriented Chemical Engineering, Nanjing Tech University, Nanjing 211816, People's Republic of China College of Biotechnology and Pharmaceutical Engineering, Nanjing Tech University, Nanjing 211816, People's Republic of China National Engineering Technique Research Center for Biotechnology, Nanjing Tech University, Nanjing 211816, People's Republic of China Present address: College of Biotechnology and Pharmaceutical Engineering, Nanjing Tech University, South Puzhu Road 30, Nanjing 211816, People's Republic of China
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16
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Activation and inhibition of CTP synthase from Trypanosoma brucei, the causative agent of African sleeping sickness. Bioorg Med Chem Lett 2011; 21:5188-90. [DOI: 10.1016/j.bmcl.2011.07.054] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2011] [Revised: 07/13/2011] [Accepted: 07/13/2011] [Indexed: 11/19/2022]
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17
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Lauritsen I, Willemoës M, Jensen KF, Johansson E, Harris P. Structure of the dimeric form of CTP synthase from Sulfolobus solfataricus. Acta Crystallogr Sect F Struct Biol Cryst Commun 2011; 67:201-8. [PMID: 21301086 PMCID: PMC3034608 DOI: 10.1107/s1744309110052334] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2010] [Accepted: 12/13/2010] [Indexed: 11/10/2022]
Abstract
CTP synthase catalyzes the last committed step in de novo pyrimidine-nucleotide biosynthesis. Active CTP synthase is a tetrameric enzyme composed of a dimer of dimers. The tetramer is favoured in the presence of the substrate nucleotides ATP and UTP; when saturated with nucleotide, the tetramer completely dominates the oligomeric state of the enzyme. Furthermore, phosphorylation has been shown to regulate the oligomeric states of the enzymes from yeast and human. The crystal structure of a dimeric form of CTP synthase from Sulfolobus solfataricus has been determined at 2.5 Å resolution. A comparison of the dimeric interface with the intermolecular interfaces in the tetrameric structures of Thermus thermophilus CTP synthase and Escherichia coli CTP synthase shows that the dimeric interfaces are almost identical in the three systems. Residues that are involved in the tetramerization of S. solfataricus CTP synthase according to a structural alignment with the E. coli enzyme all have large thermal parameters in the dimeric form. Furthermore, they are seen to undergo substantial movement upon tetramerization.
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Affiliation(s)
- Iben Lauritsen
- Department of Biology, University of Copenhagen, Ole Maaløes Vej 5, DK-2200 Copenhagen, Denmark
| | - Martin Willemoës
- Department of Biology, University of Copenhagen, Ole Maaløes Vej 5, DK-2200 Copenhagen, Denmark
| | - Kaj Frank Jensen
- Department of Biology, University of Copenhagen, Ole Maaløes Vej 5, DK-2200 Copenhagen, Denmark
| | - Eva Johansson
- Department of Chemistry, University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen, Denmark
- Diabetes Protein Engineering, Novo Nordisk A/S, Novo Nordisk Park, DK-2760 Måløv, Denmark
| | - Pernille Harris
- Department of Chemistry, Technical University of Denmark, Kemitorvet, Building 207, DK-2800 Kgs. Lyngby, Denmark
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18
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Expression, purification and analysis of the activity of enzymes from the pentose phosphate pathway. Protein Expr Purif 2010; 76:229-37. [PMID: 21111048 DOI: 10.1016/j.pep.2010.11.008] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2010] [Revised: 11/12/2010] [Accepted: 11/14/2010] [Indexed: 11/20/2022]
Abstract
RNAs, more than ever before, are increasingly viewed as biomolecules of the future, in the versatility of their functions and intricate three-dimensional folding. To effectively study them by nuclear magnetic resonance (NMR) spectroscopy, structural biologists need to tackle two critical challenges of spectral overcrowding and fast signal decay for large RNAs. Stable-isotope nucleotide labeling is one attractive solution to the overlap problem. Hence, developing effective methods for nucleotide labeling is highly desirable. In this work, we have developed a facile and streamlined source of recombinant enzymes from the pentose phosphate pathway for making such labeled nucleotides. The Escherichia coli (E. coli) genes encoding ribokinase (RK), adenine phosphoribosyltransferase (APRT), xanthine/guanine phosphoribosyltransferase (XGPRT), and uracil phosphoribosyltransferase (UPRT) were sub-cloned into pET15b vectors. All four constructs together with cytidine triphosphate synthetase (CTPS) and human phosphoribosyl pyrophosphate synthetase isoform 1 (PRPPS) were transformed into the E. coli BL21(AI) strain for protein over-expression. The enzyme preparations were purified to >90% homogeneity by a one-step Ni-NTA affinity chromatography, without the need of a further size-exclusion chromatography step. We obtained yields of 1530, 22, 482, 3120, 2120 and 2280 units of activity per liter of culture for RK, PRPPS, APRT, XGPRT, UPRT and CTPS, respectively; the specific activities were found to be 70, 22, 21, 128, 144 and 113 U/mg, respectively. These specific activities of these enzyme constructs are comparable to or higher than those previously reported. In addition, both the growth conditions and purification protocols have been streamlined so that all the recombinant proteins can be expressed, purified and characterized in at most 2 days. The availability and reliability of these constructs should make production of fully and site-specific labeled nucleotides for making labeled RNA accessible and straightforward, to facilitate high-resolution NMR spectroscopic and other biophysical studies.
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19
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Roy AC, Lunn FA, Bearne SL. Inhibition of CTP synthase from Escherichia coli by xanthines and uric acids. Bioorg Med Chem Lett 2009; 20:141-4. [PMID: 20004571 DOI: 10.1016/j.bmcl.2009.11.017] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2009] [Revised: 11/05/2009] [Accepted: 11/05/2009] [Indexed: 10/20/2022]
Abstract
CTP synthase (CTPS) catalyzes the conversion of UTP to CTP and is a recognized target for the development of anticancer, antiviral, and antiprotozoal agents. Xanthine and related compounds inhibit CTPS activity (IC(50)=0.16-0.58mM). The presence of an 8-oxo function (i.e., uric acids) enhances inhibition (IC(50)=0.060-0.121mM). An intact purine ring with anionic character favors inhibition. In general, methylation of the purine does not significantly affect inhibition.
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Affiliation(s)
- Alexander C Roy
- Department of Biochemistry and Molecular Biology, Dalhousie University, Halifax, Nova Scotia, Canada B3H 1X5
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20
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Taylor SD, Lunn FA, Bearne SL. Ground state, intermediate, and multivalent nucleotide analogue inhibitors of cytidine 5'-triphosphate synthase. ChemMedChem 2009; 3:1853-7. [PMID: 18988211 DOI: 10.1002/cmdc.200800236] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Affiliation(s)
- Scott D Taylor
- Department of Chemistry, University of Waterloo, 200 University Avenue West, Waterloo, ON N2L3G1, Canada.
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21
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Mutational analysis of conserved glycine residues 142, 143 and 146 reveals Gly(142) is critical for tetramerization of CTP synthase from Escherichia coli. Biochem J 2008; 412:113-21. [PMID: 18260824 DOI: 10.1042/bj20071163] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
CTPS (cytidine 5'-triphosphate synthase) catalyses the ATP-dependent formation of CTP from UTP using either ammonia or L-glutamine as the nitrogen source. Binding of the substrates ATP and UTP, or the product CTP, promotes oligomerization of CTPS from inactive dimers to active tetramers. In the present study, site-directed mutagenesis was used to replace the fully conserved glycine residues 142 and 143 within the UTP-binding site and 146 within the CTP-binding site of Escherchia coli CTPS. CD spectral analyses of wild-type CTPS and the glycine mutants showed a slight reduction of approximately 15% in alpha-helical content for G142A and G143A relative to G146A and wild-type CTPS, suggesting some local alterations in structure. Relative to wild-type CTPS, the values of k(cat)/K(m) for ammonia-dependent and glutamine-dependent CTP formation catalysed by G143A were reduced 22- and 16-fold respectively, whereas the corresponding values for G146A were reduced only 1.4- and 1.8-fold respectively. The glutaminase activity (k(cat)) of G146A was similar to that exhibited by the wild-type enzyme, whereas that of G143A was reduced 7.5-fold. G146A exhibited substrate inhibition at high concentrations of ammonia and a partial uncoupling of glutamine hydrolysis from CTP production. Although the apparent affinity (1/[S](0.5)) of G143A and G146A for UTP was reduced approximately 4-fold, G146A exhibited increased co-operativity with respect to UTP. Thus mutations in the CTP-binding site can affect UTP-dependent activity. Surprisingly, G142A was inactive with both ammonia and glutamine as substrates. Gel-filtration HPLC experiments revealed that both G143A and G146A were able to form active tetramers in the presence of ATP and UTP; however, nucleotide-dependent tetramerization of G142A was significantly impaired. Our observations highlight the sensitivity of the structure of CTPS to mutations in the UTP- and CTP-binding sites, with Gly(142) being critical for nucleotide-dependent oligomerization of CTPS to active tetramers. This 'structural sensitivity' may limit the number and/or types of mutations that could be selected for during the development of resistance to cytotoxic pyrimidine nucleotide analogues.
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