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Samanta A, Banerjee S, Maity TR, Jahnavi J, Datta S. Towards establishment of a plant-based model to assess the novel anti-cancerous lead molecule(s): An in silico, in vivo and in vitro assessment of some potential anti-cancerous drugs on Lathyrus sativus L. PROTOPLASMA 2022; 259:1455-1466. [PMID: 35195768 DOI: 10.1007/s00709-022-01745-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/14/2021] [Accepted: 02/09/2022] [Indexed: 06/14/2023]
Abstract
The drug development process is one of the important aspects of medical biology. The classical lead identification strategy in the way of drug development based on animal cell is time-consuming, expensive and involving ethical issues. The following study aims to develop a novel plant-based screening of drugs. Study shows the efficacy of certain anti-cancerous drugs (Pemetrexed, 5-Fluorouracil, Methotrexate, Topotecan and Etoposide) on a plant-based (Lathyrus sativus L.) system. Two important characteristics of cancer cells were observed in the colchicine-treated polyploid cell and the callus, where the chromosome numbers were unusual and the division of cells were uncontrolled respectively. With increasing concentration, the drugs significantly reduced the mitotic index, ploidy level and callus growth. Increasing Pemetrexed concentration decreased the plant DHFR activity. A decrease in total RNA content was observed in 5-FU and Methotrexate with increasing concentrations of the drugs. Etoposide and Topotecan inhibited plant topoisomerase II and topoisomerase I activities, which was justified through plasmid nicking and comet assay, respectively. Molecular and biochemical study revealed similar results to the animal system. The in silico study had been done, and the structural similarity of drug binding domains of L. sativus and human beings had also been established. The binding site of the selected drugs to the domains of plant target proteins was also determined. Experimental results are significant in terms of the efficacy of known anti-cancerous drugs on the plant-based system. The proposed assay system is a cost-effective, convenient and less time-consuming process for primary screening of anti-cancerous lead molecules.
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Affiliation(s)
- Aveek Samanta
- Department of Botany, Prabhat Kumar College, Purba Medinipur, Contai, 721401, West Bengal, India
- Department of Biotechnology, Haldia Institute of Technology, Purba Medinipur, Haldia, 721657, West Bengal, India
| | - Saptadipa Banerjee
- Department of Biotechnology, Haldia Institute of Technology, Purba Medinipur, Haldia, 721657, West Bengal, India
| | - Tilak Raj Maity
- Department of Biotechnology, Haldia Institute of Technology, Purba Medinipur, Haldia, 721657, West Bengal, India
| | - Jangala Jahnavi
- Department of Biological Sciences, Birla Institute of Technology and Science, Pilani, 333031, Rajasthan, India
| | - Siraj Datta
- Department of Biotechnology, Haldia Institute of Technology, Purba Medinipur, Haldia, 721657, West Bengal, India.
- Subarnarekha Mahavidyalaya, Gopiballavpur, Jhargram, 721506, West Bengal, India.
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2
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Fahim AM, Ismael EHI, Elsayed GH, Farag AM. Synthesis, antimicrobial, anti-proliferative activities, molecular docking and DFT studies of novel pyrazolo[5,1-c][1, 2, 4]triazine-3-carboxamide derivatives. J Biomol Struct Dyn 2021; 40:9177-9193. [PMID: 34106038 DOI: 10.1080/07391102.2021.1930582] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
In this investigation, we studied the reactivity of 5-aminouracil (1) with ethyl cyanoacetate (2) utilizing microwave irradiation to afford the corresponding 2-cyano-N-(2,4-dioxo-1,2,3,4-tetrahydropyrimidin-5-yl)acetamide (3) in excellent yield. The electrophilic azo-coupling reaction of acetamide 3 with aromatic diazonium salts afforded the corresponding hydrazone derivatives 4a-d. The Michael addition cyclization of hydrazone in pyridine to give pyrazolo[5,1-c][1, 2, 4]triazine-3-carboxamide 5a-d derivatives. The obtained compounds were elucidated against antimicrobial activity and antitumor activity breast cancer cells (MCF-7) and liver cancer cells (HepG2) utilized MTT assay. Compounds 5b, 5c and 5d revealed more inhibitory influence on MCF7 and HepG2 growth than the reference drug doxorubicin (Dox) after 48 h incubation. Furthermore, molecular docking studies were carried out on one of the most effective compound 4-amino-N-(2,4-dioxo-1,2,3,4-tetrahydropyrimidin-5-yl)-7-(4-fluorophenyl) pyrazole [5,1-c][1, 2, 4]triazine-3-carboxamide (5c) (TFC) with (PDB: 3t88), (PDB: 2wje) , (PDB: 4ynt), (PDB: 1tgh), (PDB: 4hdq) and (PDB: 3pxe) which attached with different proteins with different energies and shortage bond distance. Also; the comprehensive theoretical and experimental mechanical studies of compound TFC and TMC were compatible with FTIR and 1H NMR spectral data. The optimized molecular structure of TFC with FTIR was examined via DFT/ B3LYP/6-31G (d) level.Communicated by Ramaswamy H. Sarma.
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Affiliation(s)
- Asmaa M Fahim
- Department of Green Chemistry, National Research Center, Dokki, Cairo, Egypt
| | - Eman H I Ismael
- Department of Organometallic and Organ Metalloid Chemistry, National Research Centre, Dokki, Cairo, Egypt
| | - Ghada H Elsayed
- Hormones Department, National Research Centre, Dokki, Cairo, Egypt
| | - Ahmad M Farag
- Department of Chemistry, Faculty of Science, Cairo University, Giza, Cairo, Egypt
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Synthesis, antimicrobial and antiproliferative activities, molecular docking, and computational studies of novel heterocycles. JOURNAL OF THE IRANIAN CHEMICAL SOCIETY 2021. [DOI: 10.1007/s13738-021-02251-7] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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4
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Synthesis, antimicrobial evaluation, molecular docking and theoretical calculations of novel pyrazolo[1,5-a]pyrimidine derivatives. J Mol Struct 2020. [DOI: 10.1016/j.molstruc.2019.127025] [Citation(s) in RCA: 31] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Singh H, Kaur M, Kaur H, Sharma I, Bhandari A, Kaur G, Singh P. Structural tuning of acridones for developing anticancer agents targeting dihydrofolate reductase. Bioorg Med Chem Lett 2019; 29:126631. [PMID: 31447082 DOI: 10.1016/j.bmcl.2019.126631] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2019] [Revised: 08/16/2019] [Accepted: 08/19/2019] [Indexed: 11/25/2022]
Abstract
Targeting dihydrofolate reductase, here, we report the tumor growth inhibitory activity of substituted acridones. The screening of the molecules over 60 cell line panel of human cancer cells identified (S)-oxiran-2-ylmethyl 9-oxo-9,10-dihydroacridine-4-carboxylate (19) with average GI50 0.3 μM. The specificity of the compound to CCRF-CEM, MOLT-4 and SR cell lines of leukemia and SW-620, SF268, LOXIMVI, ACHN and MCF7 cancerous cells exhibiting GI50 in the nM range was observed. C6 Glioma cells treated with compound 19 showed differentiated cell morphology and cell cycle arrest in G2/M phase. The interactions of the compound with dihydrofolate reductase were ascertained with the help of enzyme immunoassays, molecular docking and molecular dynamic studies.
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Affiliation(s)
- Harpreet Singh
- Department of Chemistry, UGC Sponsored Centre for Advanced Studies, Guru Nanak Dev University, Amritsar 143005, India
| | - Manpreet Kaur
- Department of Chemistry, UGC Sponsored Centre for Advanced Studies, Guru Nanak Dev University, Amritsar 143005, India
| | - Harpreet Kaur
- Department of Chemistry, UGC Sponsored Centre for Advanced Studies, Guru Nanak Dev University, Amritsar 143005, India
| | - Indu Sharma
- Department of Biotechnology, Guru Nanak Dev University, Amritsar 143005, India
| | - Anmol Bhandari
- Department of Biotechnology, Guru Nanak Dev University, Amritsar 143005, India
| | - Gurcharan Kaur
- Department of Biotechnology, Guru Nanak Dev University, Amritsar 143005, India
| | - Palwinder Singh
- Department of Chemistry, UGC Sponsored Centre for Advanced Studies, Guru Nanak Dev University, Amritsar 143005, India.
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Pozzi C, Ferrari S, Luciani R, Costi MP, Mangani S. Structural and Functional Characterization of the Human Thymidylate Synthase (hTS) Interface Variant R175C, New Perspectives for the Development of hTS Inhibitors. Molecules 2019; 24:molecules24071362. [PMID: 30959951 PMCID: PMC6479699 DOI: 10.3390/molecules24071362] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2019] [Revised: 04/03/2019] [Accepted: 04/05/2019] [Indexed: 11/25/2022] Open
Abstract
Human thymidylate synthase (hTS) is pivotal for cell survival and proliferation, indeed it provides the only synthetic source of dTMP, required for DNA biosynthesis. hTS represents a validated target for anticancer chemotherapy. However, active site-targeting drugs towards hTS have limitations connected to the onset of resistance. Thus, new strategies have to be applied to effectively target hTS without inducing resistance in cancer cells. Here, we report the generation and the functional and structural characterization of a new hTS interface variant in which Arg175 is replaced by a cysteine. Arg175 is located at the interface of the hTS obligate homodimer and protrudes inside the active site of the partner subunit, in which it provides a fundamental contribution for substrate binding. Indeed, the R175C variant results catalytically inactive. The introduction of a cysteine at the dimer interface is functional for development of new hTS inhibitors through innovative strategies, such as the tethering approach. Structural analysis, performed through X-ray crystallography, has revealed that a cofactor derivative is entrapped inside the catalytic cavity of the hTS R175C variant. The peculiar binding mode of the cofactor analogue suggests new clues exploitable for the design of new hTS inhibitors.
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Affiliation(s)
- Cecilia Pozzi
- Department of Biotechnology, Chemistry and Pharmacy, Department of Excellence 2018-2020, University of Siena, via Aldo Moro 2, 53100 Siena, Italy.
| | - Stefania Ferrari
- Department of Life Sciences, University of Modena and Reggio Emilia, Via Campi 103, 41125 Modena, Italy.
| | - Rosaria Luciani
- Department of Life Sciences, University of Modena and Reggio Emilia, Via Campi 103, 41125 Modena, Italy.
| | - Maria Paola Costi
- Department of Life Sciences, University of Modena and Reggio Emilia, Via Campi 103, 41125 Modena, Italy.
| | - Stefano Mangani
- Department of Biotechnology, Chemistry and Pharmacy, Department of Excellence 2018-2020, University of Siena, via Aldo Moro 2, 53100 Siena, Italy.
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Pozzi C, Lopresti L, Santucci M, Costi MP, Mangani S. Evidence of Destabilization of the Human Thymidylate Synthase (hTS) Dimeric Structure Induced by the Interface Mutation Q62R. Biomolecules 2019; 9:biom9040134. [PMID: 30987202 PMCID: PMC6523895 DOI: 10.3390/biom9040134] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2019] [Revised: 03/31/2019] [Accepted: 04/01/2019] [Indexed: 12/13/2022] Open
Abstract
In human cells, thymidylate synthase (TS) provides the only source of 2′-deoxythymidyne-5′-monophosphate (dTMP), which is required for DNA biosynthesis. Because of its pivotal role, human TS (hTS) represents a validated target for anticancer chemotherapy. Nonetheless, the efficacy of drugs blocking the hTS active site has limitations due to the onset of resistance in cancer cells, requiring the identification of new strategies to effectively inhibit this enzyme. Human TS works as an obligate homodimer, making the inter-subunit interface an attractive targetable area. Here, we report the design and investigation of a new hTS variant, in which Gln62, located at the dimer interface, has been replaced by arginine in order to destabilize the enzyme quaternary assembly. The hTS Q62R variant has been characterized though kinetic assay, thermal denaturation analysis and X-ray crystallography. Our results provide evidence that hTS Q62R has a reduced melting temperature. The effective destabilization of the TS quaternary structure is also confirmed by structural analysis, showing that the introduced mutation induces a slight aperture of the hTS dimer. The generation of hTS variants having a more accessible interface area can facilitate the screening of interface-targeting molecules, providing key information for the rational design of innovative hTS interface inhibitors.
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Affiliation(s)
- Cecilia Pozzi
- Department of Biotechnology, Chemistry and Pharmacy-Department of Excellence 2018-2020, University of Siena, 53100 Siena, Italy.
| | - Ludovica Lopresti
- Department of Biotechnology, Chemistry and Pharmacy-Department of Excellence 2018-2020, University of Siena, 53100 Siena, Italy.
| | - Matteo Santucci
- Department of Life Sciences, University of Modena and Reggio Emilia, 41125 Modena, Italy.
| | - Maria Paola Costi
- Department of Life Sciences, University of Modena and Reggio Emilia, 41125 Modena, Italy.
| | - Stefano Mangani
- Department of Biotechnology, Chemistry and Pharmacy-Department of Excellence 2018-2020, University of Siena, 53100 Siena, Italy.
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8
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Structural Comparison of Enterococcus faecalis and Human Thymidylate Synthase Complexes with the Substrate dUMP and Its Analogue FdUMP Provides Hints about Enzyme Conformational Variabilities. Molecules 2019; 24:molecules24071257. [PMID: 30935102 PMCID: PMC6479881 DOI: 10.3390/molecules24071257] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2019] [Revised: 03/22/2019] [Accepted: 03/28/2019] [Indexed: 12/17/2022] Open
Abstract
Thymidylate synthase (TS) is an enzyme of paramount importance as it provides the only de novo source of deoxy-thymidine monophosphate (dTMP). dTMP, essential for DNA synthesis, is produced by the TS-catalyzed reductive methylation of 2′-deoxyuridine-5′-monophosphate (dUMP) using N5,N10-methylenetetrahydrofolate (mTHF) as a cofactor. TS is ubiquitous and a validated drug target. TS enzymes from different organisms differ in sequence and structure, but are all obligate homodimers. The structural and mechanistic differences between the human and bacterial enzymes are exploitable to obtain selective inhibitors of bacterial TSs that can enrich the currently available therapeutic tools against bacterial infections. Enterococcus faecalis is a pathogen fully dependent on TS for dTMP synthesis. In this study, we present four new crystal structures of Enterococcus faecalis and human TSs in complex with either the substrate dUMP or the inhibitor FdUMP. The results provide new clues about the half-site reactivity of Enterococcus faecalis TS and the mechanisms underlying the conformational changes occurring in the two enzymes. We also identify relevant differences in cofactor and inhibitor binding between Enterococcus faecalis and human TS that can guide the design of selective inhibitors against bacterial TSs.
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9
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Farag AM, Fahim AM. Synthesis, biological evaluation and DFT calculation of novel pyrazole and pyrimidine derivatives. J Mol Struct 2019. [DOI: 10.1016/j.molstruc.2018.11.008] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
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10
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Fahim AM, Shalaby MA. Synthesis, biological evaluation, molecular docking and DFT calculations of novel benzenesulfonamide derivatives. J Mol Struct 2019. [DOI: 10.1016/j.molstruc.2018.08.087] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
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11
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New Insight into the Octamer of TYMS Stabilized by Intermolecular Cys43-Disulfide. Int J Mol Sci 2018; 19:ijms19051393. [PMID: 29735940 PMCID: PMC5983622 DOI: 10.3390/ijms19051393] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2018] [Revised: 04/25/2018] [Accepted: 05/01/2018] [Indexed: 01/04/2023] Open
Abstract
Thymidylate synthase (TYMS) is an essential enzyme for the de novo synthesis of deoxythymidine monophosphate (dTMP) and has been a primary target for cancer chemotherapy. Although the physical structure of TYMS and the molecular mechanisms of TYMS catalyzing the conversion of deoxyuridine monophosphate (dUMP) to dTMP have been the subject of thorough studies, its oligomeric structure remains unclear. Here, we show that human TYMS not only exists in dimer form but also as an octamer by intermolecular Cys43-disulfide formation. We optimized the expression conditions of recombinant human TYMS using the Escherichia coli system. Using high-performance liquid chromatography⁻tandem mass spectrometry (HPLC⁻MS/MS), we have shown that purified TYMS has catalytic activity for producing dTMP. In the absence of reductant β-mercaptoethanol, SDS-PAGE and size exclusion chromatography (SEC) showed that the size of the TYMS protein is about 35 kDa, 70 kDa, and 280 kDa. When the Cys43 was mutated to Gly, the band of ~280 kDa and the peak of the octamer disappeared. Therefore, TYMS was determined to form an octamer, depending on the presence of Cys43-disulfide. By measuring steady-state parameters for the monomer, dimer, and octamer, we found the kcat of the octamer was increased slightly more than the monomer. On the basis of these findings, we suggest that the octamer in the active state might have a potential influence on the design of new drug targets.
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Deschamps P, Réty S, Bareille J, Leulliot N. Crystal structure of the active form of native human thymidylate synthase in the absence of bound substrates. Acta Crystallogr F Struct Biol Commun 2017; 73:336-341. [PMID: 28580921 PMCID: PMC5458390 DOI: 10.1107/s2053230x17007233] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2017] [Accepted: 05/16/2017] [Indexed: 11/10/2022] Open
Abstract
Human thymidylate synthase (hTS) provides the sole de novo intracellular source of thymidine 5'-monophosphate (dTMP). hTS is required for DNA replication prior to cell division, making it an attractive target for anticancer chemotherapy and drug discovery. hTS binds 2'-deoxyuridine 5'-monophosphate (dUMP) and the folate co-substrate N5,N10-methylenetetrahydrofolate (meTHF) in a pocket near the catalytic residue Cys195. The catalytic loop, which is composed of amino-acid residues 181-197, can adopt two distinct conformations related by a 180° rotation. In the active conformation Cys195 is close to the active site, while in the inactive conformation it is rotated and Cys195 is too distant from the active site for catalysis. Several hTS structures, either native or engineered, have been solved in the active conformation in complex with ligands or inhibitors and at different salt concentrations. However, apo hTS structures have been solved in an inactive conformation in high-salt and low-salt conditions (PDB entries 1ypv, 4h1i, 4gyh, 3egy and 3ehi). Here, the structure of apo hTS crystallized in the active form with sulfate ions coordinated by the arginine residue that binds dUMP is reported.
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Affiliation(s)
- P. Deschamps
- Laboratoire de Cristallographie et RMN Biologiques, UMR CNRS 8015, Université Paris Descartes, Sorbonne Paris Cité, Faculté de Pharmacie de Paris, Paris, France
| | - S. Réty
- Laboratoire de Cristallographie et RMN Biologiques, UMR CNRS 8015, Université Paris Descartes, Sorbonne Paris Cité, Faculté de Pharmacie de Paris, Paris, France
| | - J. Bareille
- Laboratoire de Cristallographie et RMN Biologiques, UMR CNRS 8015, Université Paris Descartes, Sorbonne Paris Cité, Faculté de Pharmacie de Paris, Paris, France
| | - N. Leulliot
- Laboratoire de Cristallographie et RMN Biologiques, UMR CNRS 8015, Université Paris Descartes, Sorbonne Paris Cité, Faculté de Pharmacie de Paris, Paris, France
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Anderson KS. Understanding the molecular mechanism of substrate channeling and domain communication in protozoal bifunctional TS-DHFR. Protein Eng Des Sel 2017; 30:253-261. [PMID: 28338744 PMCID: PMC6438133 DOI: 10.1093/protein/gzx004] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2016] [Revised: 12/14/2016] [Accepted: 12/15/2016] [Indexed: 11/13/2022] Open
Abstract
Most species, such as humans, have monofunctional forms of thymidylate synthase (TS) and dihydrofolate reductase (DHFR) that are key folate metabolism enzymes making critical folate components required for DNA synthesis. In contrast, several parasitic protozoa, including Leishmania major (Lm), Plasmodium falciparum (Pf), Toxoplasma gondii (Tg) and Cryptosporidium hominis (Ch), contain a unique bifunctional thymidylate synthase-dihydrofolate reductase (TS-DHFR) having the two sequential catalytic activities contained on a single polypeptide chain. It has been suggested that the bifunctional nature of the two catalytic activities may enable substrate channeling. The 3D structures for each of these enzymes reveals distinct features for each species. While three of the four species (Pf, Tg and Ch) contain a junctional region linking the two domains, this is lacking in Lm. The Lm and Pf contain N-terminal amino acid extensions. A multidisciplinary approach using structural studies and transient kinetic analyses combined with mutational analysis has investigated the roles of these unique structural features for each enzyme. Additionally, the possibility of substrate channeling behavior was explored. These studies have identified unique, functional regions in both the TS and DHFR domains that govern efficient catalysis for each species. Surprisingly, even though there are structural similarities among the species, each is regulated in a distinct manner. This structural and mechanistic information was also used to exploit species-specific inhibitor design.
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Affiliation(s)
- Karen S. Anderson
- Departments of Pharmacology and Molecular Biophysics and Biochemistry,
Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520-8066, USA
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Choi YM, Yeo HK, Park YW, Lee JY. Structural Analysis of Thymidylate Synthase from Kaposi's Sarcoma-Associated Herpesvirus with the Anticancer Drug Raltitrexed. PLoS One 2016; 11:e0168019. [PMID: 27936107 PMCID: PMC5148040 DOI: 10.1371/journal.pone.0168019] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2016] [Accepted: 11/25/2016] [Indexed: 01/07/2023] Open
Abstract
Kaposi's sarcoma-associated herpesvirus (KSHV) is a highly infectious human herpesvirus that causes Kaposi's sarcoma. KSHV encodes functional thymidylate synthase, which is a target for anticancer drugs such as raltitrexed or 5-fluorouracil. Thymidylate synthase catalyzes the conversion of 2'-deoxyuridine-5'-monophosphate (dUMP) to thymidine-5'-monophosphate (dTMP) using 5,10-methylenetetrahydrofolate (mTHF) as a co-substrate. The crystal structures of thymidylate synthase from KSHV (apo), complexes with dUMP (binary), and complexes with both dUMP and raltitrexed (ternary) were determined at 1.7 Å, 2.0 Å, and 2.4 Å, respectively. While the ternary complex structures of human thymidylate synthase and E. coli thymidylate synthase had a closed conformation, the ternary complex structure of KSHV thymidylate synthase was observed in an open conformation, similar to that of rat thymidylate synthase. The complex structures of KSHV thymidylate synthase did not have a covalent bond between the sulfhydryl group of Cys219 and C6 atom of dUMP, unlike the human thymidylate synthase. The catalytic Cys residue demonstrated a dual conformation in the apo structure, and its sulfhydryl group was oriented toward the C6 atom of dUMP with no covalent bond upon ligand binding in the complex structures. These structural data provide the potential use of antifolates such as raltitrexed as a viral induced anticancer drug and structural basis to design drugs for targeting the thymidylate synthase of KSHV.
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Affiliation(s)
- Yong Mi Choi
- Department of Life Science, Dongguk University-Seoul, Ilsandong-gu, Goyang-si, Gyeonggi-do, Republic of Korea
| | - Hyun Ku Yeo
- Department of Life Science, Dongguk University-Seoul, Ilsandong-gu, Goyang-si, Gyeonggi-do, Republic of Korea
| | - Young Woo Park
- Department of Life Science, Dongguk University-Seoul, Ilsandong-gu, Goyang-si, Gyeonggi-do, Republic of Korea
| | - Jae Young Lee
- Department of Life Science, Dongguk University-Seoul, Ilsandong-gu, Goyang-si, Gyeonggi-do, Republic of Korea
- * E-mail:
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Folates as adjuvants to anticancer agents: Chemical rationale and mechanism of action. Crit Rev Oncol Hematol 2016; 106:118-31. [PMID: 27637357 DOI: 10.1016/j.critrevonc.2016.08.001] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2015] [Revised: 07/01/2016] [Accepted: 08/09/2016] [Indexed: 12/31/2022] Open
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16
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Johnson B, Vanderwalde A, Javadi N, Feldman R, Reddy SB. Molecular profiling of a case of advanced pancreatic cancer identifies an active and tolerable combination of targeted therapy with backbone chemotherapy. J Gastrointest Oncol 2016; 7:E6-E12. [PMID: 27034805 PMCID: PMC4783749 DOI: 10.3978/j.issn.2078-6891.2015.091] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/22/2015] [Accepted: 08/01/2015] [Indexed: 12/11/2022] Open
Abstract
Typical survival with common 1(st)-line regimens for pancreatic cancer range from 6-11 months. We report a case of a patient with stage IVB pancreatic adenocarcinoma treated with gemcitabine and erlotinib who stopped therapy after 3 months without achieving a response due to intolerance. To decide upon additional treatment options, molecular analysis was performed on liver metastasis which revealed KRAS, FBXW7, APC, and ATM mutations, with thymidylate synthase (TS) negativity and PD-1 positivity. Based on this profile of TS negativity and ATM mutation, a combination strategy was devised consisting of capecitabine, oxaliplatin, bevacizumab and vorinostat. The patient had a near complete response to therapy with this regimen. In refractory metastatic pancreatic cancer, responses of this magnitude are rarely seen. To our knowledge, this represents the first demonstrated activity of this combination in the metastatic setting which could prompt further investigation of its use in large scale clinical trials.
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Singh P, Kumar A, Kaur S, Kaur J, Singh H. The bioinspired design of a reagent allows the functionalization of Cα-H of α,β-unsaturated carbonyl compounds via the Baylis-Hillman chemistry under ambient conditions. Chem Commun (Camb) 2016; 52:2936-9. [PMID: 26779574 DOI: 10.1039/c5cc08830e] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
A rationally designed reagent capable of affecting alkylation at Cα of α,β-unsaturated carbonyl compounds is reported. The reaction proceeded at room temperature without any additives. The pH and H-bond formation during the reaction play a key role in the working of the reagent.
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Affiliation(s)
- Palwinder Singh
- Department of Chemistry, UGC Sponsored Centre for Advanced Studies, Guru Nanak Dev University, Amritsar-143005, India.
| | - Arun Kumar
- Department of Chemistry, UGC Sponsored Centre for Advanced Studies, Guru Nanak Dev University, Amritsar-143005, India.
| | - Sukhmeet Kaur
- Department of Chemistry, UGC Sponsored Centre for Advanced Studies, Guru Nanak Dev University, Amritsar-143005, India.
| | - Jagroop Kaur
- Department of Chemistry, UGC Sponsored Centre for Advanced Studies, Guru Nanak Dev University, Amritsar-143005, India.
| | - Harpreet Singh
- Department of Chemistry, UGC Sponsored Centre for Advanced Studies, Guru Nanak Dev University, Amritsar-143005, India.
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Hew K, Dahlroth SL, Veerappan S, Pan LX, Cornvik T, Nordlund P. Structure of the Varicella Zoster Virus Thymidylate Synthase Establishes Functional and Structural Similarities as the Human Enzyme and Potentiates Itself as a Target of Brivudine. PLoS One 2015; 10:e0143947. [PMID: 26630264 PMCID: PMC4668047 DOI: 10.1371/journal.pone.0143947] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2015] [Accepted: 11/11/2015] [Indexed: 12/19/2022] Open
Abstract
Varicella zoster virus (VZV) is a highly infectious human herpesvirus that is the causative agent for chicken pox and shingles. VZV encodes a functional thymidylate synthase (TS), which is the sole enzyme that produces dTMP from dUMP de novo. To study substrate binding, the complex structure of TSVZV with dUMP was determined to a resolution of 2.9 Å. In the absence of a folate co-substrate, dUMP binds in the conserved TS active site and is coordinated similarly as in the human encoded TS (TSHS) in an open conformation. The interactions between TSVZV with dUMP and a cofactor analog, raltitrexed, were also studied using differential scanning fluorimetry (DSF), suggesting that TSVZV binds dUMP and raltitrexed in a sequential binding mode like other TS. The DSF also revealed interactions between TSVZV and in vitro phosphorylated brivudine (BVDUP), a highly potent anti-herpesvirus drug against VZV infections. The binding of BVDUP to TSVZV was further confirmed by the complex structure of TSVZV and BVDUP solved at a resolution of 2.9 Å. BVDUP binds similarly as dUMP in the TSHS but it induces a closed conformation of the active site. The structure supports that the 5-bromovinyl substituent on BVDUP is likely to inhibit TSVZV by preventing the transfer of a methylene group from its cofactor and the subsequent formation of dTMP. The interactions between TSVZV and BVDUP are consistent with that TSVZV is indeed a target of brivudine in vivo. The work also provided the structural basis for rational design of more specific TSVZV inhibitors.
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Affiliation(s)
- Kelly Hew
- Division of Structural Biology and Biochemistry, Nanyang Technological University, School of Biological Sciences, Singapore, Singapore
| | - Sue-Li Dahlroth
- Division of Structural Biology and Biochemistry, Nanyang Technological University, School of Biological Sciences, Singapore, Singapore
| | - Saranya Veerappan
- Division of Structural Biology and Biochemistry, Nanyang Technological University, School of Biological Sciences, Singapore, Singapore
| | - Lucy Xin Pan
- Division of Structural Biology and Biochemistry, Nanyang Technological University, School of Biological Sciences, Singapore, Singapore
| | - Tobias Cornvik
- Division of Structural Biology and Biochemistry, Nanyang Technological University, School of Biological Sciences, Singapore, Singapore
| | - Pär Nordlund
- Division of Structural Biology and Biochemistry, Nanyang Technological University, School of Biological Sciences, Singapore, Singapore
- Division of Biophysics, Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Stockholm, Sweden
- Institute of Molecular and Cell Biology, Agency for Science, Technology and Research, Singapore, Singapore
- * E-mail:
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19
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Singh P, Kumar A, Kaur S, Singh A. Thymidylate synthase inspired biomodel reagent for the conversion of uracil to thymine. Chem Commun (Camb) 2015; 51:9961-4. [PMID: 25997777 DOI: 10.1039/c5cc03312h] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Inspired by TSase catalysis for dUMP conversion to dTMP, a biomodel reagent is developed. The presence of NH2, Gly-(S)-Cys and (S)-oxiran methyl, at C5, C4 and N-10 of acridine, respectively, in addition to the pH of the reaction mixture, allows for good complementary inter- and intra-molecular interactions and chiral discrimination for the reagent to achieve conversion of uracil to thymine.
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Affiliation(s)
- Palwinder Singh
- Department of Chemistry, UGC Sponsored Centre for Advanced Studies, Guru Nanak Dev University, Amritsar-143005, India.
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20
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Wakasa K, Kawabata R, Nakao S, Hattori H, Taguchi K, Uchida J, Yamanaka T, Maehara Y, Fukushima M, Oda S. Dynamic modulation of thymidylate synthase gene expression and fluorouracil sensitivity in human colorectal cancer cells. PLoS One 2015; 10:e0123076. [PMID: 25881233 PMCID: PMC4400010 DOI: 10.1371/journal.pone.0123076] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2014] [Accepted: 02/27/2015] [Indexed: 11/18/2022] Open
Abstract
Biomarkers have revolutionized cancer chemotherapy. However, many biomarker candidates are still in debate. In addition to clinical studies, a priori experimental approaches are needed. Thymidylate synthase (TS) expression is a long-standing candidate as a biomarker for 5-fluorouracil (5-FU) treatment of cancer patients. Using the Tet-OFF system and a human colorectal cancer cell line, DLD-1, we first constructed an in vitro system in which TS expression is dynamically controllable. Quantitative assays have elucidated that TS expression in the transformant was widely modulated, and that the dynamic range covered 15-fold of the basal level. 5-FU sensitivity of the transformant cells significantly increased in response to downregulated TS expression, although being not examined in the full dynamic range because of the doxycycline toxicity. Intriguingly, our in vitro data suggest that there is a linear relationship between TS expression and the 5-FU sensitivity in cells. Data obtained in a mouse model using transformant xenografts were highly parallel to those obtained in vitro. Thus, our in vitro and in vivo observations suggest that TS expression is a determinant of 5-FU sensitivity in cells, at least in this specific genetic background, and, therefore, support the possibility of TS expression as a biomarker for 5-FU-based cancer chemotherapy.
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Affiliation(s)
- Kentaro Wakasa
- Clinical Research Institute, National Kyushu Cancer Center, Fukuoka, Japan
| | - Rumi Kawabata
- Tokushima Research Center, Taiho Pharmaceutical Co., Ltd., Tokushima, Japan
| | - Seiki Nakao
- Clinical Research Institute, National Kyushu Cancer Center, Fukuoka, Japan
| | | | - Kenichi Taguchi
- Clinical Research Institute, National Kyushu Cancer Center, Fukuoka, Japan
| | - Junji Uchida
- Tokushima Research Center, Taiho Pharmaceutical Co., Ltd., Tokushima, Japan
| | - Takeharu Yamanaka
- Department of Biostatistics, Yokohama City University, Yokohama, Japan
| | - Yoshihiko Maehara
- Department of Surgery and Science, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan
| | - Masakazu Fukushima
- Clinical Research Institute, National Kyushu Cancer Center, Fukuoka, Japan
| | - Shinya Oda
- Clinical Research Institute, National Kyushu Cancer Center, Fukuoka, Japan
- * E-mail:
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21
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Salo-Ahen OMH, Tochowicz A, Pozzi C, Cardinale D, Ferrari S, Boum Y, Mangani S, Stroud RM, Saxena P, Myllykallio H, Costi MP, Ponterini G, Wade RC. Hotspots in an obligate homodimeric anticancer target. Structural and functional effects of interfacial mutations in human thymidylate synthase. J Med Chem 2015; 58:3572-81. [PMID: 25798950 DOI: 10.1021/acs.jmedchem.5b00137] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Human thymidylate synthase (hTS), a target for antiproliferative drugs, is an obligate homodimer. Single-point mutations to alanine at the monomer-monomer interface may enable the identification of specific residues that delineate sites for drugs aimed at perturbing the protein-protein interactions critical for activity. We computationally identified putative hotspot residues at the interface and designed mutants to perturb the intersubunit interaction. Dimer dissociation constants measured by a FRET-based assay range from 60 nM for wild-type hTS up to about 1 mM for single-point mutants and agree with computational predictions of the effects of these mutations. Mutations that are remote from the active site retain full or partial activity, although the substrate KM values were generally higher and the dimer was less stable. The lower dimer stability of the mutants can facilitate access to the dimer interface by small molecules and thereby aid the design of inhibitors that bind at the dimer interface.
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Affiliation(s)
- Outi M H Salo-Ahen
- †Molecular and Cellular Modeling Group, Heidelberg Institute for Theoretical Studies, 69118 Heidelberg, Germany
| | - Anna Tochowicz
- ‡Department of Biochemistry and Biophysics, University of California-San Francisco, San Francisco, California 94158, United States
| | - Cecilia Pozzi
- §Department of Biotechnology, Chemistry and Pharmacy, University of Siena, 53100 Siena, Italy
| | - Daniela Cardinale
- ∥Department of Life Sciences, University of Modena and Reggio Emilia, 41125 Modena, Italy
| | - Stefania Ferrari
- ∥Department of Life Sciences, University of Modena and Reggio Emilia, 41125 Modena, Italy
| | - Yap Boum
- ⊥Ecole Polytechnique, CNRS UMR7645, INSERM U696, 91128 Palaiseau, France
| | - Stefano Mangani
- §Department of Biotechnology, Chemistry and Pharmacy, University of Siena, 53100 Siena, Italy
| | - Robert M Stroud
- ‡Department of Biochemistry and Biophysics, University of California-San Francisco, San Francisco, California 94158, United States
| | - Puneet Saxena
- ∥Department of Life Sciences, University of Modena and Reggio Emilia, 41125 Modena, Italy
| | - Hannu Myllykallio
- ⊥Ecole Polytechnique, CNRS UMR7645, INSERM U696, 91128 Palaiseau, France
| | - Maria Paola Costi
- ∥Department of Life Sciences, University of Modena and Reggio Emilia, 41125 Modena, Italy
| | - Glauco Ponterini
- ∥Department of Life Sciences, University of Modena and Reggio Emilia, 41125 Modena, Italy
| | - Rebecca C Wade
- †Molecular and Cellular Modeling Group, Heidelberg Institute for Theoretical Studies, 69118 Heidelberg, Germany.,#Center for Molecular Biology, DKFZ-ZMBH Alliance, and Interdisciplinary Center for Scientific Computing (IWR), Heidelberg University, 69120 Heidelberg, Germany
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22
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Tochowicz A, Santucci M, Saxena P, Guaitoli G, Trande M, Finer-Moore J, Stroud RM, Costi MP. Alanine mutants of the interface residues of human thymidylate synthase decode key features of the binding mode of allosteric anticancer peptides. J Med Chem 2014; 58:1012-8. [PMID: 25427005 DOI: 10.1021/jm5011176] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Allosteric peptide inhibitors of thymidylate synthase (hTS) bind to the dimer interface and stabilize the inactive form of the protein. Four interface residues were mutated to alanine, and interaction studies were employed to decode the key role of these residues in the peptide molecular recognition. This led to the identification of three crucial interface residues F59, L198, and Y202 that impart activity to the peptide inhibitors and suggest the binding area for further inhibitor design.
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Affiliation(s)
- Anna Tochowicz
- Department of Biochemistry and Biophysics, University of California-San Francisco , 600 16th Street, San Francisco, California 94158, United States
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23
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Abstract
Expression of hTS (human thymidylate synthase), a key enzyme in thymidine biosynthesis, is regulated on the translational level through a feedback mechanism that is rarely found in eukaryotes. At low substrate concentrations, the ligand-free enzyme binds to its own mRNA and stabilizes a hairpin structure that sequesters the start codon. When in complex with dUMP (2'-deoxyuridine-5'-monophosphate) and a THF (tetrahydrofolate) cofactor, the enzyme adopts a conformation that is unable to bind and repress expression of mRNA. Here, we have used a combination of X-ray crystallography, RNA mutagenesis and site-specific cross-linking studies to investigate the molecular recognition of TS mRNA by the hTS enzyme. The interacting mRNA region was narrowed to the start codon and immediately flanking sequences. In the hTS enzyme, a helix-loop-helix domain on the protein surface was identified as the putative RNA-binding site.
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24
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Schmidt C, Irausquin SJ, Valafar H. Advances in the REDCAT software package. BMC Bioinformatics 2013; 14:302. [PMID: 24098943 PMCID: PMC3840585 DOI: 10.1186/1471-2105-14-302] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2013] [Accepted: 09/13/2013] [Indexed: 12/24/2022] Open
Abstract
Background Residual Dipolar Couplings (RDCs) have emerged in the past two decades as an informative source of experimental restraints for the study of structure and dynamics of biological macromolecules and complexes. The REDCAT software package was previously introduced for the analysis of molecular structures using RDC data. Here we report additional features that have been included in this software package in order to expand the scope of its analyses. We first discuss the features that enhance REDCATs user-friendly nature, such as the integration of a number of analyses into one single operation and enabling convenient examination of a structural ensemble in order to identify the most suitable structure. We then describe the new features which expand the scope of RDC analyses, performing exercises that utilize both synthetic and experimental data to illustrate and evaluate different features with regard to structure refinement and structure validation. Results We establish the seamless interaction that takes place between REDCAT, VMD, and Xplor-NIH in demonstrations that utilize our newly developed REDCAT-VMD and XplorGUI interfaces. These modules enable visualization of RDC analysis results on the molecular structure displayed in VMD and refinement of structures with Xplor-NIH, respectively. We also highlight REDCAT’s Error-Analysis feature in reporting the localized fitness of a structure to RDC data, which provides a more effective means of recognizing local structural anomalies. This allows for structurally sound regions of a molecule to be identified, and for any refinement efforts to be focused solely on locally distorted regions. Conclusions The newly engineered REDCAT software package, which is available for download via the WWW from http://ifestos.cse.sc.edu, has been developed in the Object Oriented C++ environment. Our most recent enhancements to REDCAT serve to provide a more complete RDC analysis suite, while also accommodating a more user-friendly experience, and will be of great interest to the community of researchers and developers since it hides the complications of software development.
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Affiliation(s)
- Chris Schmidt
- Department of Computer Science & Engineering, University of South Carolina, Columbia, SC 29208, USA.
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25
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Sharma H, Landau MJ, Vargo MA, Spasov KA, Anderson KS. First three-dimensional structure of Toxoplasma gondii thymidylate synthase-dihydrofolate reductase: insights for catalysis, interdomain interactions, and substrate channeling. Biochemistry 2013; 52:7305-7317. [PMID: 24053355 DOI: 10.1021/bi400576t] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Most species, such as humans, have monofunctional forms of thymidylate synthase (TS) and dihydrofolate reductase (DHFR) that are key folate metabolism enzymes making critical folate components required for DNA synthesis. In contrast, several parasitic protozoa, including Toxoplasma gondii , contain a unique bifunctional thymidylate synthase-dihydrofolate reductase (TS-DHFR) having the catalytic activities contained on a single polypeptide chain. The prevalence of T. gondii infections across the world, especially for those immunocompromised, underscores the need to understand TS-DHFR enzyme function and to find new avenues to exploit for the design of novel antiparasitic drugs. As a first step, we have solved the first three-dimensional structures of T. gondii TS-DHFR at 3.7 Å and of a loop truncated TS-DHFR, removing several flexible surface loops in the DHFR domain, improving resolution to 2.2 Å. Distinct structural features of the TS-DHFR homodimer include a junctional region containing a kinked crossover helix between the DHFR domains of the two adjacent monomers, a long linker connecting the TS and DHFR domains, and a DHFR domain that is positively charged. The roles of these unique structural features were probed by site-directed mutagenesis coupled with presteady state and steady state kinetics. Mutational analysis of the crossover helix region combined with kinetic characterization established the importance of this region not only in DHFR catalysis but also in modulating the distal TS activity, suggesting a role for TS-DHFR interdomain interactions. Additional kinetic studies revealed that substrate channeling occurs in which dihydrofolate is directly transferred from the TS to DHFR active site without entering bulk solution. The crystal structure suggests that the positively charged DHFR domain governs this electrostatically mediated movement of dihydrofolate, preventing release from the enzyme. Taken together, these structural and kinetic studies reveal unique, functional regions on the T. gondii TS-DHFR enzyme that may be targeted for inhibition, thus paving the way for designing species specific inhibitors.
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Affiliation(s)
- Hitesh Sharma
- The Department of Pharmacology, Yale University School of Medicine, New Haven, CT 06510
| | - Mark J Landau
- The Department of Pharmacology, Yale University School of Medicine, New Haven, CT 06510.,The Department of Molecular Biophysics and Biochemistry, Yale University School of Medicine, New Haven, CT 06510
| | - Melissa A Vargo
- The Department of Pharmacology, Yale University School of Medicine, New Haven, CT 06510
| | - Krasimir A Spasov
- The Department of Pharmacology, Yale University School of Medicine, New Haven, CT 06510
| | - Karen S Anderson
- The Department of Pharmacology, Yale University School of Medicine, New Haven, CT 06510.,The Department of Molecular Biophysics and Biochemistry, Yale University School of Medicine, New Haven, CT 06510
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26
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Landau MJ, Sharma H, Anderson KS. Selective peptide inhibitors of bifunctional thymidylate synthase-dihydrofolate reductase from Toxoplasma gondii provide insights into domain-domain communication and allosteric regulation. Protein Sci 2013; 22:1161-73. [PMID: 23813474 DOI: 10.1002/pro.2300] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2013] [Revised: 06/14/2013] [Accepted: 06/17/2013] [Indexed: 11/05/2022]
Abstract
The bifunctional enzyme thymidylate synthase-dihydrofolate reductase (TS-DHFR) plays an essential role in DNA synthesis and is unique to several species of pathogenic protozoans, including the parasite Toxoplasma gondii. Infection by T. gondii causes the prevalent disease toxoplasmosis, for which TS-DHFR is a major therapeutic target. Here, we design peptides that target the dimer interface between the TS domains of bifunctional T. gondii TS-DHFR by mimicking β-strands at the interface, revealing a previously unknown allosteric target. The current study shows that these β-strand mimetic peptides bind to the apo-enzyme in a species-selective manner to inhibit both the TS and distal DHFR. Fluorescence spectroscopy was used to monitor conformational switching of the TS domain and demonstrate that these peptides induce a conformational change in the enzyme. Using structure-guided mutagenesis, nonconserved residues in the linker between TS and DHFR were identified that play a key role in domain-domain communication and in peptide inhibition of the DHFR domain. These studies validate allosteric inhibition of apo-TS, specifically at the TS-TS interface, as a potential target for novel, species-specific therapeutics for treating T. gondii parasitic infections and overcoming drug resistance.
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Affiliation(s)
- Mark J Landau
- Department of Pharmacology, Yale University School of Medicine, 333 Cedar Street, New Haven, Connecticut, 06510; Department of Molecular Biophysics and Biochemistry, Yale University School of Medicine, 333 Cedar Street, New Haven, Connecticut, 06510
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27
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Lu Y, Zhuo C, Cui B, Liu Z, Zhou P, Lu Y, Wang B. TYMS serves as a prognostic indicator to predict the lymph node metastasis in Chinese patients with colorectal cancer. Clin Biochem 2013; 46:1478-83. [PMID: 23810585 DOI: 10.1016/j.clinbiochem.2013.06.017] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2013] [Revised: 06/16/2013] [Accepted: 06/17/2013] [Indexed: 11/26/2022]
Abstract
OBJECTIVE The current study is to evaluate the effect of thymidylate synthase (TYMS) on lymph node metastasis (LNM) in Chinese colorectal cancer (CRC) patients, and develop potential LNM-associated biomarkers for CRC. DESIGN AND METHODS Differences in TYMS gene expression between primary CRC with LNM (LNM CRC) and without LNM (non-LNM CRC) were assessed using quantitative real-time PCR analysis in 100 Chinese colorectal cancer patients. The relationship between clinicopathological parameters and prognosis of candidate biomarkers was also examined in the experiment. RESULTS TYMS was significantly upregulated in LNM CRC compared with non-LNM CRC, which was confirmed by real-time quantitative polymerase chain reaction. Overexpression of TYMS was significantly associated with LNM (P<0.001), advanced TNM stage (P<0.001), increased 5-year recurrence rate (P<0.001) and decreased 5-year overall survival rate (P<0.001). Univariate and multivariate analyses indicated that TYMS expression was an independent prognostic factor for recurrence and survival of CRC patients (P<0.05). CONCLUSIONS TYMS effect on lymph node metastasis in CRC might serve as a potential biomarker for LNM and a prognostic factor in CRC. Over-expression of TYMS is a predicting factor to the poor outcome in clinical colorectal cancer patients.
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Affiliation(s)
- Yuanfang Lu
- Department of Clinical Research Center, Affiliated 2nd Hospital of Nanjing Medical University, Jiang Jiayuan 121, Xiaguan District, Nanjing 210011, PR China
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28
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Characterization of the bipartite degron that regulates ubiquitin-independent degradation of thymidylate synthase. Biosci Rep 2013. [PMID: 23181752 PMCID: PMC3549573 DOI: 10.1042/bsr20120112] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
TS (thymidylate synthase) is a key enzyme in the de novo biosynthesis of dTMP, and is indispensable for DNA replication. Previous studies have shown that intracellular degradation of the human enzyme [hTS (human thymidylate synthase)] is mediated by the 26S proteasome, and occurs in a ubiquitin-independent manner. Degradation of hTS is governed by a degron that is located at the polypeptide's N-terminus that is capable of promoting the destabilization of heterologous proteins to which it is attached. The hTS degron is bipartite, consisting of two subdomains: an IDR (intrinsically disordered region) that is highly divergent among mammalian species, followed by a conserved amphipathic α-helix (designated hA). In the present report, we have characterized the structure and function of the hTS degron in more detail. We have conducted a bioinformatic analysis of interspecies sequence variation exhibited by the IDR, and find that its hypervariability is not due to diversifying (or positive) selection; rather, it has been subjected to purifying (or negative) selection, although the intensity of such selection is relaxed or weakened compared with that exerted on the rest of the molecule. In addition, we have verified that both subdomains of the hTS degron are required for full activity. Furthermore, their co-operation does not necessitate that they are juxtaposed, but is maintained when they are physically separated. Finally, we have identified a 'cryptic' degron at the C-terminus of hTS, which is activated by the N-terminal degron and appears to function only under certain circumstances; its role in TS metabolism is not known.
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29
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Pozzi C, Ferrari S, Cortesi D, Luciani R, Stroud RM, Catalano A, Costi MP, Mangani S. The structure of Enterococcus faecalis thymidylate synthase provides clues about folate bacterial metabolism. ACTA CRYSTALLOGRAPHICA. SECTION D, BIOLOGICAL CRYSTALLOGRAPHY 2012; 68:1232-41. [PMID: 22948925 PMCID: PMC10316677 DOI: 10.1107/s0907444912026236] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/15/2012] [Accepted: 06/10/2012] [Indexed: 11/11/2022]
Abstract
Drug resistance to therapeutic antibiotics poses a challenge to the identification of novel targets and drugs for the treatment of infectious diseases. Infections caused by Enterococcus faecalis are a major health problem. Thymidylate synthase (TS) from E. faecalis is a potential target for antibacterial therapy. The X-ray crystallographic structure of E. faecalis thymidylate synthase (EfTS), which was obtained as a native binary complex composed of EfTS and 5-formyltetrahydrofolate (5-FTHF), has been determined. The structure provides evidence that EfTS is a half-of-the-sites reactive enzyme, as 5-FTHF is bound to two of the four independent subunits present in the crystal asymmetric unit. 5-FTHF is a metabolite of the one-carbon transfer reaction catalysed by 5-formyltetrahydrofolate cyclo-ligase. Kinetic studies show that 5-FTHF is a weak inhibitor of EfTS, suggesting that the EfTS-5-FTHF complex may function as a source of folates and/or may regulate one-carbon metabolism. The structure represents the first example of endogenous 5-FTHF bound to a protein involved in folate metabolism.
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Affiliation(s)
- Cecilia Pozzi
- Dipartimento di Chimica, University of Siena, Via Aldo Moro 2, 53100 Siena, Italy
| | - Stefania Ferrari
- Dipartimento di Scienze Farmaceutiche, University of Modena and Reggio Emilia, Via Campi 183, 41126 Modena, Italy
| | - Debora Cortesi
- Dipartimento di Scienze Farmaceutiche, University of Modena and Reggio Emilia, Via Campi 183, 41126 Modena, Italy
| | - Rosaria Luciani
- Dipartimento di Scienze Farmaceutiche, University of Modena and Reggio Emilia, Via Campi 183, 41126 Modena, Italy
| | - Robert M. Stroud
- Department of Biochemistry and Biophysiscs, University of California, San Francisco, S-412C Genentech Hall, 600 16th Street, San Francisco, CA 94158-2517, USA
| | - Alessia Catalano
- Dipartimento Farmaco-Chimico, University of Bari ‘Aldo Moro’, Via E. Orabona 4, 70125 Bari, Italy
| | - Maria Paola Costi
- Dipartimento di Scienze Farmaceutiche, University of Modena and Reggio Emilia, Via Campi 183, 41126 Modena, Italy
| | - Stefano Mangani
- Dipartimento di Chimica, University of Siena, Via Aldo Moro 2, 53100 Siena, Italy
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30
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Begley DW, Edwards TE, Raymond AC, Smith ER, Hartley RC, Abendroth J, Sankaran B, Lorimer DD, Myler PJ, Staker BL, Stewart LJ. Inhibitor-bound complexes of dihydrofolate reductase-thymidylate synthase from Babesia bovis. Acta Crystallogr Sect F Struct Biol Cryst Commun 2011; 67:1070-7. [PMID: 21904052 PMCID: PMC3169404 DOI: 10.1107/s1744309111029009] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2011] [Accepted: 07/18/2011] [Indexed: 02/03/2023]
Abstract
Babesiosis is a tick-borne disease caused by eukaryotic Babesia parasites which are morphologically similar to Plasmodium falciparum, the causative agent of malaria in humans. Like Plasmodium, different species of Babesia are tuned to infect different mammalian hosts, including rats, dogs, horses and cattle. Most species of Plasmodium and Babesia possess an essential bifunctional enzyme for nucleotide synthesis and folate metabolism: dihydrofolate reductase-thymidylate synthase. Although thymidylate synthase is highly conserved across organisms, the bifunctional form of this enzyme is relatively uncommon in nature. The structural characterization of dihydrofolate reductase-thymidylate synthase in Babesia bovis, the causative agent of babesiosis in livestock cattle, is reported here. The apo state is compared with structures that contain dUMP, NADP and two different antifolate inhibitors: pemetrexed and raltitrexed. The complexes reveal modes of binding similar to that seen in drug-resistant malaria strains and point to the utility of applying structural studies with proven cancer chemotherapies towards infectious disease research.
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Affiliation(s)
- Darren W Begley
- Seattle Structural Genomics Center for Infectious Disease (http://www.ssgcid.org), USA.
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31
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Melo SP, Barbour KW, Berger FG. Cooperation between an intrinsically disordered region and a helical segment is required for ubiquitin-independent degradation by the proteasome. J Biol Chem 2011; 286:36559-67. [PMID: 21878626 DOI: 10.1074/jbc.m111.274258] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The 26 S proteasomal complex, which is responsible for the bulk of protein degradation within the cell, recognizes its target substrates via covalently linked polyubiquitin moieties. However, a small but growing number of proteasomal substrates are degraded without a requirement for ubiquitinylation. One such substrate is the pyrimidine biosynthetic enzyme thymidylate synthase (EC 2.1.1.45), which catalyzes the synthesis of TMP and is the sole de novo source of TTP for DNA replication and repair. Previous work showed that intracellular proteolysis of human thymidylate synthase is directed by a degron at the polypeptide's N-terminal end, composed of an intrinsically disordered region (IDR) followed by a highly conserved amphipathic α-helix (hA). In the present report, we show that the hA helix does not function simply as an extension or scaffold for the IDR; rather, it provides a specific structural component that is necessary for degradation. Furthermore, its helical conformation is required for this function. We demonstrate that small domains from heterologous proteins can substitute for the IDR and the hA helix of human thymidylate synthase, indicating that the degradation-promoting function of these regions is not sequence-specific. The results, in general, indicate that cooperation between intrinsically disordered domains and α-helical segments is required for ubiquitin-independent degradation by the proteasome. There appears to be little sequence constraint on the ability of these regions to function as degron constituents. Rather, it is the overall conformation (or lack thereof) that is critical.
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Affiliation(s)
- Sandra P Melo
- Department of Biological Sciences and Center for Colon Cancer Research, University of South Carolina, Columbia, South Carolina 29208, USA
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The active-inactive transition of human thymidylate synthase: Targeted molecular dynamics simulations. Proteins 2011; 79:2886-99. [DOI: 10.1002/prot.23123] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2011] [Revised: 05/13/2011] [Accepted: 06/15/2011] [Indexed: 12/11/2022]
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Protein-protein interface-binding peptides inhibit the cancer therapy target human thymidylate synthase. Proc Natl Acad Sci U S A 2011; 108:E542-9. [PMID: 21795601 DOI: 10.1073/pnas.1104829108] [Citation(s) in RCA: 68] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Human thymidylate synthase is a homodimeric enzyme that plays a key role in DNA synthesis and is a target for several clinically important anticancer drugs that bind to its active site. We have designed peptides to specifically target its dimer interface. Here we show through X-ray diffraction, spectroscopic, kinetic, and calorimetric evidence that the peptides do indeed bind at the interface of the dimeric protein and stabilize its di-inactive form. The "LR" peptide binds at a previously unknown binding site and shows a previously undescribed mechanism for the allosteric inhibition of a homodimeric enzyme. It inhibits the intracellular enzyme in ovarian cancer cells and reduces cellular growth at low micromolar concentrations in both cisplatin-sensitive and -resistant cells without causing protein overexpression. This peptide demonstrates the potential of allosteric inhibition of hTS for overcoming platinum drug resistance in ovarian cancer.
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Luo B, Johnson SR, Lebioda L, Berger SH. Evolution of metamorphism in thymidylate synthases within the primate lineages. J Mol Evol 2011; 72:306-14. [PMID: 21318388 DOI: 10.1007/s00239-011-9433-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2010] [Accepted: 01/25/2011] [Indexed: 10/18/2022]
Abstract
Crystal structures of human thymidylate synthase (hTS) revealed that the protein exists in active and inactive conformations, defined by the position of a loop containing the active site nucleophile. TS is highly homologous among diverse species; however, the residue at position 163 (hTS) differs among species. Arginine at this position is predicted by structural modeling to enable conformational switching. Arginine or lysine is reported at this position in all mammals in the GenBank and Ensembl databases, with arginine reported in only primates. Sequence analysis of the TS gene of representative primates revealed that arginine occurs at this relative position in all primates except a representative of prosimians. Mutant human proteins were created with residues at position 163 that occur in TSs from prokaryotes and eukaryotes. Catalytic constants (k(cat)) of mutant enzymes were 45-149% of hTS, with the lysine mutant (R163K) exhibiting the highest k(cat). The effect of lysine substitution on solution structure and on ligand binding was investigated. R163K exhibited higher intrinsic fluorescence, a more negative molar ellipticity, and higher dissociation constants (K(d)) for ligands that modulate protein conformation than hTS. Temperature effects on intrinsic fluorescence and catalytic activity of hTS and R163K are consistent with proteins populating different conformational states. The data indicate that the enzyme with arginine at the position corresponding to 163 (hTS) evolved after the divergence of prosimians and simians and that substitution of lysine by arginine confers unique structural and functional properties to the enzyme expressed in simian primates.
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Affiliation(s)
- BeiBei Luo
- Department of Pharmaceutical and Biomedical Sciences, South Carolina College of Pharmacy, University of South Carolina, 700 Sumter Street, Columbia, SC 29208, USA
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35
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Gibson LM, Celeste LR, Lovelace LL, Lebioda L. Structures of human thymidylate synthase R163K with dUMP, FdUMP and glutathione show asymmetric ligand binding. ACTA CRYSTALLOGRAPHICA. SECTION D, BIOLOGICAL CRYSTALLOGRAPHY 2011; 67:60-6. [PMID: 21206062 PMCID: PMC3016017 DOI: 10.1107/s0907444910044732] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/18/2010] [Accepted: 11/01/2010] [Indexed: 11/10/2022]
Abstract
Thymidylate synthase (TS) is a well validated target in cancer chemotherapy. Here, a new crystal form of the R163K variant of human TS (hTS) with five subunits per asymmetric part of the unit cell, all with loop 181-197 in the active conformation, is reported. This form allows binding studies by soaking crystals in artificial mother liquors containing ligands that bind in the active site. Using this approach, crystal structures of hTS complexes with FdUMP and dUMP were obtained, indicating that this form should facilitate high-throughput analysis of hTS complexes with drug candidates. Crystal soaking experiments using oxidized glutathione revealed that hTS binds this ligand. Interestingly, the two types of binding observed are both asymmetric. In one subunit of the physiological dimer covalent modification of the catalytic nucleophile Cys195 takes place, while in another dimer a noncovalent adduct with reduced glutathione is formed in one of the active sites.
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Affiliation(s)
- Lydia M. Gibson
- Department of Chemistry and Biochemistry, University of South Carolina, Columbia, South Carolina 29208, USA
| | - Lesa R. Celeste
- Department of Chemistry and Biochemistry, University of South Carolina, Columbia, South Carolina 29208, USA
| | - Leslie L. Lovelace
- Department of Chemistry and Biochemistry, University of South Carolina, Columbia, South Carolina 29208, USA
| | - Lukasz Lebioda
- Department of Chemistry and Biochemistry, University of South Carolina, Columbia, South Carolina 29208, USA
- Center for Colon Cancer Research, University of South Carolina, Columbia, South Carolina 29208, USA
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36
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Abstract
Human thymidylate synthase (hTS; EC 2.1.1.45) is one of a small group of proteasomal substrates whose intracellular degradation occurs in a ubiquitin-independent manner. Previous studies have shown that proteolytic breakdown of the hTS polypeptide is directed by an intrinsically disordered 27-residue domain at the N-terminal end of the molecule. This domain, in co-operation with an α-helix spanning amino acids 31–45, functions as a degron, in that it has the ability to destabilize a heterologous polypeptide to which it is attached. In the present study, we provide evidence indicating that it is the 26S isoform of the proteasome that is responsible for intracellular degradation of the hTS polypeptide. In addition, we have used targeted in vitro mutagenesis to show that an Arg–Arg motif at residues 10–11 is required for proteolysis, an observation that was confirmed by functional analysis of the TS N-terminus from other mammalian species. The effects of stabilizing mutations on hTS degradation are maintained when the enzyme is provided with an alternative means of proteasome association; thus such mutations perturb one or more post-docking steps in the degradation pathway. Surprisingly, deletion mutants missing large segments of the disordered domain still function as proteasomal substrates; however, degradation of such mutants occurs by a mechanism that is distinct from that for the wild-type protein. Taken together, our results provide information on the roles of specific subregions within the intrinsically disordered N-terminal domain of hTS in regulation of degradation, leading to a deeper understanding of mechanisms underlying the ubiquitin-independent proteasomal degradation pathway.
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Garg D, Henrich S, Salo-Ahen OMH, Myllykallio H, Costi MP, Wade RC. Novel approaches for targeting thymidylate synthase to overcome the resistance and toxicity of anticancer drugs. J Med Chem 2010; 53:6539-49. [PMID: 20527892 DOI: 10.1021/jm901869w] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Affiliation(s)
- Divita Garg
- Molecular and Cellular Modeling Group, Heidelberg Institute of Theoretical Studies gGmbH, Heidelberg, Germany
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38
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Begley DW, Zheng S, Varani G. Fragment-based discovery of novel thymidylate synthase leads by NMR screening and group epitope mapping. Chem Biol Drug Des 2010; 76:218-33. [PMID: 20626411 DOI: 10.1111/j.1747-0285.2010.01010.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Solution-state nuclear magnetic resonance (NMR) is a versatile tool for the study of binding interactions between small molecules and macromolecular targets. We applied ligand-based NMR techniques to the study of human thymidylate synthase (hTS) using known nanomolar inhibitors and a library of small molecule fragments. Screening by NMR led to the rapid identification of ligand pairs that bind in proximal sites within the cofactor-binding pocket of hTS. Screening hits were used as search criteria within commercially available sources, and a subset of catalog analogs were tested for potency by in vitro assay and binding affinity by quantitative saturation transfer difference (STD)-NMR titration. Two compounds identified by this approach possess low micromolar affinity and potency, as well as excellent binding efficiency against hTS. Relative binding orientations for both leads were modeled using AutoDock, and the most likely bound conformations were validated using experimentally derived STD-NMR binding epitope data. These ligands represent novel starting points for fragment-based drug design of non-canonical TS inhibitors, and their binding epitopes highlight important and previously unexploited interactions with conserved residues in the cofactor-binding site.
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Affiliation(s)
- Darren W Begley
- Department of Chemistry, University of Washington, Box 351700, Seattle, WA 98195-1700, USA.
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39
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Formation of catalytically active cross-species heterodimers of thymidylate synthase from Plasmodium falciparum and Plasmodium vivax. Mol Biol Rep 2010; 38:1029-37. [PMID: 20577818 DOI: 10.1007/s11033-010-0199-7] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2009] [Accepted: 06/11/2010] [Indexed: 10/19/2022]
Abstract
Thymidylate synthase (TS) of Plasmodium dihydrofolate reductase-thymidylate synthase (DHFR-TS) functions as a homodimeric enzyme with two active sites located near the subunit interface. The dimerization is essential for catalysis, since the active site of each subunit contains amino acid residues contributed from the other TS domain. In P. falciparum DHFR-TS, it has been shown that the active sites require Cys-490 from one domain and Arg-470 donated from the other domain. Mutants of these two series can complement one another giving rise to active enzyme. Here, the potential to form cross-species heterodimers between P. falciparum and P. vivax TS has been explored. Formation of cross-species heterodimer was tested by co-transformation of TS-inactive Cys-490 mutants of P. falciparum or P. vivax with corresponding TS-inactive Arg-486 mutants of P. vivax or P. falciparum into thymidine-requiring Escherichia coli. Active heterodimers were detected by subunit complementation and 6-[(3)H]-FdUMP binding assays. All combinations of the mutants tested, except for (Pf)R470A+(Pv)C506Y, were able to form catalytically active cross-species heterodimers. The single active site formed by (Pf)R470D+(Pv)C506Y and (Pv)R486D+(Pf)C490A pairs of cross-species heterodimers has k(cat) and K(m) values similar to those of intra-species heterodimers of P. falciparum and P. vivax. This is the first report to demonstrate that the TS subunit interface between Plasmodium species is sufficiently conserved to allow formation of fully active cross-species heterodimer.
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40
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Huang X, Gibson LM, Bell BJ, Lovelace LL, Peña MMO, Berger FG, Berger SH, Lebioda L. Replacement of Val3 in human thymidylate synthase affects its kinetic properties and intracellular stability . Biochemistry 2010; 49:2475-82. [PMID: 20151707 DOI: 10.1021/bi901457e] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Human and other mammalian thymidylate synthase (TS) enzymes have an N-terminal extension of approximately 27 amino acids that is not present in bacterial TSs. The extension, which is disordered in all reported crystal structures of TSs, has been considered to play a primary role in protein turnover but not in catalytic activity. In mammalian cells, the variant V3A has a half-life similar to that of wild-type human TS (wt hTS) while V3T is much more stable; V3L, V3F, and V3Y have half-lives approximately half of that for wt hTS. Catalytic turnover rates for most Val3 mutants are only slightly diminished, as expected. However, two mutants, V3L and V3F, have strongly compromised dUMP binding, with K(m,app) values increased by factors of 47 and 58, respectively. For V3L, this observation can be explained by stabilization of the inactive conformation of the loop of residues 181-197, which prevents substrate binding. In the crystal structure of V3L, electron density corresponding to a leucine residue is present in a position that stabilizes the loop of residues 181-197 in the inactive conformation. Since this density is not observed in other mutants and all other leucine residues are ordered in this structure, it is likely that this density represents Leu3. In the crystal structure of a V3F.FdUMP binary complex, the nucleotide is bound in an alternative mode to that proposed for the catalytic complex, indicating that the high K(m,app) value is caused not by stabilization of the inactive conformer but by substrate binding in a nonproductive, inhibitory site. These observations show that the N-terminal extension affects the conformational state of the hTS catalytic region. Each of the mechanisms leading to the high K(m,app) values can be exploited to facilitate design of compounds acting as allosteric inhibitors of hTS.
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Affiliation(s)
- Xiao Huang
- Department of Chemistry and Biochemistry, University of South Carolina, Columbia, South Carolina 29208, USA
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41
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Srivastava V, Gupta SP, Siddiqi MI, Mishra BN. Molecular docking studies on quinazoline antifolate derivatives as human thymidylate synthase inhibitors. Bioinformation 2010; 4:357-65. [PMID: 20975900 PMCID: PMC2951674 DOI: 10.6026/97320630004357] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2009] [Accepted: 11/15/2009] [Indexed: 11/29/2022] Open
Abstract
We have performed molecular docking on quinazoline antifolates complexed with human thymidylate synthase to gain insight into the structural
preferences of these inhibitors. The study was conducted on a selected set of one hundred six compounds with variation in structure and activity.
The structural analyses indicate that the coordinate bond interactions, the hydrogen bond interactions, the van der Waals interactions as well as
the hydrophobic interactions between ligand and receptor are responsible simultaneously for the preference of inhibition and potency. In this
study, fast flexible docking simulations were performed on quinazoline antifolates derivatives as human thymidylate synthase inhibitors. The
results indicated that the quinazoline ring of the inhibitors forms hydrophobic contacts with Leu192, Leu221 and Tyr258 and stacking interaction
is conserved in complex with the inhibitor and cofactor.
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Affiliation(s)
- Vivek Srivastava
- Department of Biotechnology, Meerut Institute of Engineering & Technology, Meerut-250005; Department of Biotechnology, Institute of Engineering & Technology, UP Technical University, Sitapur Road, Lucknow 226021
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42
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Furuta E, Okuda H, Kobayashi A, Watabe K. Metabolic genes in cancer: their roles in tumor progression and clinical implications. Biochim Biophys Acta Rev Cancer 2010; 1805:141-52. [PMID: 20122995 DOI: 10.1016/j.bbcan.2010.01.005] [Citation(s) in RCA: 136] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2009] [Revised: 01/11/2010] [Accepted: 01/24/2010] [Indexed: 12/12/2022]
Abstract
Re-programming of metabolic pathways is a hallmark of physiological changes in cancer cells. The expression of certain genes that directly control the rate of key metabolic pathways including glycolysis, lipogenesis and nucleotide synthesis are drastically altered at different stages of tumor progression. These alterations are generally considered as an adaptation of tumor cells; however, they also contribute to the progression of tumor cells to become more aggressive phenotypes. This review summarizes the recent information about the mechanistic link of these genes to oncogenesis and their potential utility as diagnostic markers as well as for therapeutic targets. We particularly focus on three groups of genes; GLUT1, G6PD, TKTL1 and PGI/AMF in glycolytic pathway, ACLY, ACC1 and FAS in lipogenesis and RRM2, p53R2 and TYMS for nucleotide synthesis. All these genes are highly up-regulated in a variety of tumor cells in cancer patients, and they play active roles in tumor progression rather than expressing merely as a consequence of phenotypic change of the cancer cells. Molecular dissection of their orchestrated networks and understanding the exact mechanism of their expression will provide a window of opportunity to target these genes for specific cancer therapy. We also reviewed existing database of gene microarray to validate the utility of these genes for cancer diagnosis.
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Affiliation(s)
- Eiji Furuta
- Department of Medical Microbiology and Immunology, Southern Illinois University School of Medicine, Springfield, Illinois, USA
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43
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Zhao X, Li F, Zhuang W, Xue X, Lian Y, Fan J, Fang D. A New Method for Synthesis of Nolatrexed Dihydrochloride. Org Process Res Dev 2010. [DOI: 10.1021/op9002517] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Xueqing Zhao
- Fujian Provincial Key Laboratory of Screening for Novel Microbial Products, Fujian Institute of Microbiology, Fuzhou 350007, P.R. China, Department of Medicinal Chemistry, Nanjing Medical University, Nanjing 210029, P.R. China, and Department of Medicinal Chemistry, China Pharmaceutical University, Nanjing 210009, P.R. China
| | - Fei Li
- Fujian Provincial Key Laboratory of Screening for Novel Microbial Products, Fujian Institute of Microbiology, Fuzhou 350007, P.R. China, Department of Medicinal Chemistry, Nanjing Medical University, Nanjing 210029, P.R. China, and Department of Medicinal Chemistry, China Pharmaceutical University, Nanjing 210009, P.R. China
| | - Weiping Zhuang
- Fujian Provincial Key Laboratory of Screening for Novel Microbial Products, Fujian Institute of Microbiology, Fuzhou 350007, P.R. China, Department of Medicinal Chemistry, Nanjing Medical University, Nanjing 210029, P.R. China, and Department of Medicinal Chemistry, China Pharmaceutical University, Nanjing 210009, P.R. China
| | - Xiaowen Xue
- Fujian Provincial Key Laboratory of Screening for Novel Microbial Products, Fujian Institute of Microbiology, Fuzhou 350007, P.R. China, Department of Medicinal Chemistry, Nanjing Medical University, Nanjing 210029, P.R. China, and Department of Medicinal Chemistry, China Pharmaceutical University, Nanjing 210009, P.R. China
| | - Yuanyang Lian
- Fujian Provincial Key Laboratory of Screening for Novel Microbial Products, Fujian Institute of Microbiology, Fuzhou 350007, P.R. China, Department of Medicinal Chemistry, Nanjing Medical University, Nanjing 210029, P.R. China, and Department of Medicinal Chemistry, China Pharmaceutical University, Nanjing 210009, P.R. China
| | - Jianhui Fan
- Fujian Provincial Key Laboratory of Screening for Novel Microbial Products, Fujian Institute of Microbiology, Fuzhou 350007, P.R. China, Department of Medicinal Chemistry, Nanjing Medical University, Nanjing 210029, P.R. China, and Department of Medicinal Chemistry, China Pharmaceutical University, Nanjing 210009, P.R. China
| | - Dongsheng Fang
- Fujian Provincial Key Laboratory of Screening for Novel Microbial Products, Fujian Institute of Microbiology, Fuzhou 350007, P.R. China, Department of Medicinal Chemistry, Nanjing Medical University, Nanjing 210029, P.R. China, and Department of Medicinal Chemistry, China Pharmaceutical University, Nanjing 210009, P.R. China
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44
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Cardinale D, Salo-Ahen OMH, Guaitoli G, Ferrari S, Venturelli A, Franchini S, Battini R, Ponterini G, Wade RC, Costi MP. Design and characterization of a mutation outside the active site of human thymidylate synthase that affects ligand binding. Protein Eng Des Sel 2009; 23:81-9. [PMID: 19955218 DOI: 10.1093/protein/gzp075] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Owing to its central role in DNA synthesis, human thymidylate synthase (hTS) is a well-established target for chemotherapeutic agents, such as fluoropyrimidines. The use of hTS inhibitors in cancer therapy is limited by their toxicity and the development of cellular drug resistance. Here, with the aim of shedding light on the structural role of the A-helix in fluoropyrimidine resistance, we have created a fluoropyrimidine-resistant mutant by making a single point mutation, Glu30Trp. We postulated that residue 30, which is located in the A-helix, close to but outside the enzyme active site, could have a long-range effect on inhibitor binding. The mutant shows 100 times lower specific activity with respect to the wild-type hTS and is resistant to the classical inhibitor, FdUMP, as shown by a 6-fold higher inhibition constant. Circular dichroism experiments show that the mutant is folded. The results of molecular modeling and simulation suggest that the Glu30Trp mutation gives rise to resistance by altering the hydrogen-bond network between residue 30 and the active site.
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Affiliation(s)
- D Cardinale
- Dipartimento di Scienze Farmaceutiche, Università degli Studi di Modena e Reggio Emilia, Via Campi 183, 41100Modena, Italy
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45
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Lovelace LL, Johnson SR, Gibson LM, Bell BJ, Berger SH, Lebioda L. Variants of human thymidylate synthase with loop 181-197 stabilized in the inactive conformation. Protein Sci 2009; 18:1628-36. [PMID: 19569192 DOI: 10.1002/pro.171] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Loop 181-197 of human thymidylate synthase (hTS) populates two major conformations, essentially corresponding to the loop flipped by 180 degrees . In one of the conformations, the catalytic Cys195 residue lies distant from the active site making the enzyme inactive. Ligands stabilizing this inactive conformation may function as allosteric inhibitors. To facilitate the search for such inhibitors, we have expressed and characterized several mutants designed to shift the equilibrium toward the inactive conformer. In most cases, the catalytic efficiency of the mutants was only somewhat impaired with values of k(cat)/K(m) reduced by factors in a 2-12 range. One of the mutants, M190K, is however unique in having the value of k(cat)/K(m) smaller by a factor of approximately 7500 than the wild type. The crystal structure of this mutant is similar to that of the wt hTS with loop 181-197 in the inactive conformation. However, the direct vicinity of the mutation, residues 188-194 of this loop, assumes a different conformation with the positions of C(alpha) shifted up to 7.2 A. This affects region 116-128, which became ordered in M190K while it is disordered in wt. The conformation of 116-128 is however different than that observed in hTS in the active conformation. The side chain of Lys190 does not form contacts and is in solvent region. The very low activity of M190K as compared to another mutant with a charged residue in this position, M190E, suggests that the protein is trapped in an inactive state that does not equilibrate easily with the active conformer.
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Affiliation(s)
- Leslie L Lovelace
- Department of Chemistry and Biochemistry, University of South Carolina, Columbia, South Carolina 29208, USA
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46
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Peña MMO, Melo SP, Xing YY, White K, Barbour KW, Berger FG. The intrinsically disordered N-terminal domain of thymidylate synthase targets the enzyme to the ubiquitin-independent proteasomal degradation pathway. J Biol Chem 2009; 284:31597-607. [PMID: 19797058 DOI: 10.1074/jbc.m109.038455] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The ubiquitin-independent proteasomal degradation pathway is increasingly being recognized as important in regulation of protein turnover in eukaryotic cells. One substrate of this pathway is the pyrimidine biosynthetic enzyme thymidylate synthase (TS; EC 2.1.1.45), which catalyzes the reductive methylation of dUMP to form dTMP and is essential for DNA replication during cell growth and proliferation. Previous work from our laboratory showed that degradation of TS is ubiquitin-independent and mediated by an intrinsically disordered 27-residue region at the N-terminal end of the molecule. In the current study we show that this region, in cooperation with an alpha-helix formed by the next 15 residues, functions as a degron, i.e. it is capable of destabilizing a heterologous protein to which it is fused. Comparative analysis of the primary sequence of TS from a number of mammalian species revealed that the N-terminal domain is hypervariable among species yet is conserved with regard to its disordered nature, its high Pro content, and the occurrence of Pro at the penultimate site. Characterization of mutant proteins showed that Pro-2 protects the N terminus against N(alpha)-acetylation, a post-translational process that inhibits TS degradation. However, although a free amino group at the N terminus is necessary, it is not sufficient for degradation of the polypeptide. The implications of these findings to the proteasome-targeting function of the N-terminal domain, particularly with regard to its intrinsic flexibility, are discussed.
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Affiliation(s)
- Maria Marjorette O Peña
- Department of Biological Sciences, University of South Carolina, Columbia, South Carolina 29208, USA
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47
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Gibson LM, Lovelace LL, Lebioda L. The R163K mutant of human thymidylate synthase is stabilized in an active conformation: structural asymmetry and reactivity of cysteine 195. Biochemistry 2008; 47:4636-43. [PMID: 18370400 DOI: 10.1021/bi7019386] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Loop 181-197 of human thymidylate synthase (hTS) populates two conformational states. In the first state, Cys195, a residue crucial for catalytic activity, is in the active site (active conformer); in the other conformation, it is about 10 A away, outside the active site (inactive conformer). We have designed and expressed an hTS variant, R163K, in which the inactive conformation is destabilized. The activity of this mutant is 33% higher than that of wt hTS, suggesting that at least one-third of hTS populates the inactive conformer. Crystal structures of R163K in two different crystal forms, with six and two subunits per asymmetric part of the unit cells, have been determined. All subunits of this mutant are in the active conformation while wt hTS crystallizes as the inactive conformer in similar mother liquors. The structures show differences in the environment of catalytic Cys195, which correlate with Cys195 thiol reactivity, as judged by its oxidation state. Calculations show that the molecular electrostatic potential at Cys195 differs between the subunits of the dimer. One of the dimers is asymmetric with a phosphate ion bound in only one of the subunits. In the absence of the phosphate ion, that is in the inhibitor-free enzyme, the tip of loop 47-53 is about 11 A away from the active site.
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Affiliation(s)
- Lydia M Gibson
- Department of Chemistry and Biochemistry and Center for Colon Cancer Research, University of South Carolina, Columbia, SC 29208, USA
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48
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Lovelace LL, Gibson LM, Lebioda L. Cooperative inhibition of human thymidylate synthase by mixtures of active site binding and allosteric inhibitors. Biochemistry 2007; 46:2823-30. [PMID: 17297914 PMCID: PMC2516748 DOI: 10.1021/bi061309j] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Thymidylate synthase (TS) is a target in the chemotherapy of colorectal cancer and some other neoplasms. It catalyzes the transfer of a methyl group from methylenetetrahydrofolate to dUMP to form dTMP. On the basis of structural considerations, we have introduced 1,3-propanediphosphonic acid (PDPA) as an allosteric inhibitor of human TS (hTS); it is proposed that PDPA acts by stabilizing an inactive conformer of loop 181-197. Kinetic studies showed that PDPA is a mixed (noncompetitive) inhibitor versus dUMP. In contrast, versus methylenetrahydrofolate at concentrations lower than 0.25 microM, PDPA is an uncompetitive inhibitor, while at PDPA concentrations higher than 1 microM the inhibiton is noncompetive, as expected. At the concentrations corresponding to uncompetitive inhibition, PDPA shows positive cooperativity with an antifolate inhibitor, ZD9331, which binds to the active conformer. PDPA binding leads to the formation of hTS tetramers, but not higher oligomers. These data are consistent with a model in which hTS exists preferably as an asymmetric dimer with one subunit in the active conformation of loop 181-197 and the other in the inactive conformation.
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Affiliation(s)
- Leslie L. Lovelace
- Department of Chemistry and Biochemistry, University of South Carolina, Columbia, South Carolina 29208
| | - Lydia M. Gibson
- Department of Chemistry and Biochemistry, University of South Carolina, Columbia, South Carolina 29208
| | - Lukasz Lebioda
- Department of Chemistry and Biochemistry, University of South Carolina, Columbia, South Carolina 29208
- Center for Colon Cancer Research, University of South Carolina, Columbia, South Carolina 29208
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Du C, Niu R, Chu E, Zhang P, Lin X. Sequence analysis and functional study of thymidylate synthase from zebrafish, Danio rerio. J Biochem 2006; 139:913-20. [PMID: 16751599 DOI: 10.1093/jb/mvj100] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The thymidylate synthase (TS), an important target for many anticancer drugs, has been cloned from different species. But the cDNA property and function of TS in zebrafish are not well documented. In order to use zebrafish as an animal model for screening novel anticancer agents, we isolated TS cDNA from zebrafish and compared its sequence with those from other species. The open reading frame (ORF) of zebrafish TS cDNA sequence was 954 nucleotides, encoding a 318-amino acid protein with a calculated molecular mass of 36.15 kDa. The deduced amino acid sequence of zebrafish TS was similar to those from other organisms, including rat, mouse and humans. The zebrafish TS protein was expressed in Escherichia coli and purified to homogeneity. The purified zebrafish TS showed maximal activity at 28 degrees C with similar K(m) value to human TS. Western immunoblot assay confirmed that TS was expressed in all the developmental stages of zebrafish with a high level of expression at the 1-4 cell stages. To study the function of TS in zebrafish embryo development, a short hairpin RNA (shRNA) expression vector, pSilencer 4.1-CMV/TS, was constructed which targeted the protein-coding region of zebrafish TS mRNA. Significant change in the development of tail and epiboly was found in zebrafish embryos microinjected pSilencer4.1-CMV/TS siRNA expression vector.
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Affiliation(s)
- Changqing Du
- Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China
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50
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Peña M, Xing Y, Koli S, Berger F. Role of N-terminal residues in the ubiquitin-independent degradation of human thymidylate synthase. Biochem J 2006; 394:355-63. [PMID: 16259621 PMCID: PMC1386034 DOI: 10.1042/bj20051479] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Thymidylate synthase (TS) catalyses the reductive methylation of dUMP to form dTMP, a reaction that is essential for maintenance of nucleotide pools during cell growth. Because the enzyme is indispensable for DNA replication in actively dividing cells, it is an important target for cytotoxic drugs used in cancer chemotherapy, including fluoropyrimidines (e.g. 5-fluorouracil and 5-fluoro-2'-deoxyuridine) and anti-folates (e.g. raltitrexed, LY231514, ZD9331 and BW1843U89). These drugs generate metabolites that bind to the enzyme's active site and inhibit catalytic activity, leading to thymidylate deprivation and cellular apoptosis. Ligand binding to TS results in stabilization of the enzyme and an increase in its intracellular concentration. Previously, we showed that degradation of the TS polypeptide is carried out by the 26 S proteasome in a ubiquitin-independent manner. Such degradation is directed by the disordered N-terminal region of the TS polypeptide, and is abrogated by ligand binding. In the present study, we have verified the ubiquitin-independent nature of TS proteolysis by showing that a 'lysine-less' polypeptide, in which all lysine residues were replaced by arginine, is still subject to proteasome-mediated degradation. In addition, we have mapped the structural determinants of intracellular TS degradation in more detail and show that residues at the N-terminal end of the molecule, particularly the penultimate amino acid Pro2, play an important role in governing the half-life of the enzyme. This region is capable on its own of destabilizing an evolutionarily distinct TS molecule that normally lacks this domain, indicating that it functions as a degradation signal. Interestingly, degradation of an intrinsically unstable mutant form of TS, containing a Pro-->Leu substitution at residue 303, is directed by C-terminal, rather than N-terminal, sequences. The implications of these findings for the control of TS expression, and for the regulation of protein degradation in general, are discussed.
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Affiliation(s)
- Maria Marjorette O. Peña
- Department of Biological Sciences, University of South Carolina, 715 Sumter Street, Columbia, SC 29208, U.S.A
| | - Yang Yang Xing
- Department of Biological Sciences, University of South Carolina, 715 Sumter Street, Columbia, SC 29208, U.S.A
| | - Sangita Koli
- Department of Biological Sciences, University of South Carolina, 715 Sumter Street, Columbia, SC 29208, U.S.A
| | - Franklin G. Berger
- Department of Biological Sciences, University of South Carolina, 715 Sumter Street, Columbia, SC 29208, U.S.A
- To whom correspondence should be addressed (email )
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