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Asano A, Nakagawa M, Miyajima C, Yasui M, Minoura K, Yamada T, Doi M. Effect of the powerful plasticity of the tert-butyl side chain on the conformational equilibrium of ascidiacyclamides. J Pept Sci 2021; 27:e3363. [PMID: 34462993 DOI: 10.1002/psc.3363] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2021] [Revised: 07/28/2021] [Accepted: 07/31/2021] [Indexed: 11/06/2022]
Abstract
Ascidiacyclamide [cyclo(-Ile1,5 -oxazoline2,6 -d-Val3,7 -thiazole4,8 -)2 ] is a cytotoxic cyclic peptide from ascidian. Through structural analyses using monosubstituted analogues (Xaa1 : Ala, 2-aminobutyric acid, Val, cyclohexylglycine, and phenylglycine), we previously demonstrated the conformational equilibrium between its square and folded forms. As the bulkiness of the Xaa1 residue side chain was reduced, spontaneous folding was promoted, and the cytotoxicity decreased accordingly. In the present study, five disubstituted analogues in which a tert-leucine residue (Tle) was incorporated at the 5-position of the abovementioned monosubstituted analogues were synthesized, after which their structures were analyzed using X-ray diffraction, circular dichroism (CD) spectral measurements, and 1 H NMR-based quantitative analysis. The side chains of the Tle and Ile residues are structural isomers of one another, and the Tle residue bearing the tert-butyl group can be expected to play a role as a building block. In fact, peptides incorporating Tle5 exhibited much less spontaneous folding than their Ile5 counterparts in both crystal and solution. Increases in enthalpy and entropy due to the tert-butyl group during the folding process resulted in increased conformational free energy (ΔG°). The powerful plasticity of the tert-butyl group would stabilize the square form relating with cytotoxicity.
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Affiliation(s)
- Akiko Asano
- Faculty of Pharmacy, Osaka Medical and Pharmaceutical University, Osaka, Japan
| | - Maki Nakagawa
- Faculty of Pharmacy, Osaka Medical and Pharmaceutical University, Osaka, Japan
| | - Chihiro Miyajima
- Faculty of Pharmacy, Osaka Medical and Pharmaceutical University, Osaka, Japan
| | - Mami Yasui
- Faculty of Pharmacy, Osaka Medical and Pharmaceutical University, Osaka, Japan
| | - Katsuhiko Minoura
- Faculty of Pharmacy, Osaka Medical and Pharmaceutical University, Osaka, Japan
| | - Takeshi Yamada
- Faculty of Pharmacy, Osaka Medical and Pharmaceutical University, Osaka, Japan
| | - Mitsunobu Doi
- Faculty of Pharmacy, Osaka Medical and Pharmaceutical University, Osaka, Japan
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2
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Tebbi A, Guittet O, Tuphile K, Cabrié A, Lepoivre M. Caspase-dependent Proteolysis of Human Ribonucleotide Reductase Small Subunits R2 and p53R2 during Apoptosis. J Biol Chem 2015; 290:14077-90. [PMID: 25878246 DOI: 10.1074/jbc.m115.649640] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2015] [Indexed: 11/06/2022] Open
Abstract
Ribonucleotide reductase (RnR) is a key enzyme synthesizing deoxyribonucleotides for DNA replication and repair. In mammals, the R1 catalytic subunit forms an active complex with either one of the two small subunits R2 and p53R2. Expression of R2 is S phase-specific and required for DNA replication. The p53R2 protein is expressed throughout the cell cycle and in quiescent cells where it provides dNTPs for mitochondrial DNA synthesis. Participation of R2 and p53R2 in DNA repair has also been suggested. In this study, we investigated the fate of the RnR subunits during apoptosis. The p53R2 protein was cleaved in a caspase-dependent manner in K-562 cells treated with inhibitors of the Bcr-Abl oncogenic kinase and in HeLa 229 cells incubated with TNF-α and cycloheximide. The cleavage site was mapped between Asp(342) and Asn(343). Caspase attack released a C-terminal p53R2 peptide of nine residues containing the conserved heptapeptide essential for R1 binding. As a consequence, the cleaved p53R2 protein was inactive. In vitro, purified caspase-3 and -8 could release the C-terminal tail of p53R2. Knocking down these caspases, but not caspase-2, -7, and -10, also inhibited p53R2 cleavage in cells committed to die via the extrinsic death receptor pathway. The R2 subunit was subjected to caspase- and proteasome-dependent proteolysis, which was prevented by siRNA targeting caspase-8. Knocking down caspase-3 was ineffective. Protein R1 was not subjected to degradation. Adding deoxyribonucleosides to restore dNTP pools transiently protected cells from apoptosis. These data identify RnR activity as a prosurvival function inactivated by proteolysis during apoptosis.
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Affiliation(s)
- Ali Tebbi
- From the Université Paris Sud, Institute of Molecular and Cellular Biochemistry and Biophysics, UMR 8619, 91405 Orsay, France, CNRS, 91405 Orsay, France, and Department of Virology, Institut Pasteur, Pathogenesis of Hepatitis B Virus, 75015 Paris, France
| | - Olivier Guittet
- From the Université Paris Sud, Institute of Molecular and Cellular Biochemistry and Biophysics, UMR 8619, 91405 Orsay, France, CNRS, 91405 Orsay, France, and
| | - Karine Tuphile
- From the Université Paris Sud, Institute of Molecular and Cellular Biochemistry and Biophysics, UMR 8619, 91405 Orsay, France, CNRS, 91405 Orsay, France, and
| | - Aimeric Cabrié
- From the Université Paris Sud, Institute of Molecular and Cellular Biochemistry and Biophysics, UMR 8619, 91405 Orsay, France, CNRS, 91405 Orsay, France, and
| | - Michel Lepoivre
- From the Université Paris Sud, Institute of Molecular and Cellular Biochemistry and Biophysics, UMR 8619, 91405 Orsay, France, CNRS, 91405 Orsay, France, and
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3
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Tholander F, Sjöberg BM. Discovery of antimicrobial ribonucleotide reductase inhibitors by screening in microwell format. Proc Natl Acad Sci U S A 2012; 109:9798-803. [PMID: 22665797 PMCID: PMC3382500 DOI: 10.1073/pnas.1113051109] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Ribonucleotide reductase (RNR) catalyzes reduction of the four different ribonucleotides to their corresponding deoxyribonucleotides and is the rate-limiting enzyme in DNA synthesis. RNR is a well-established target for the antiproliferative drugs Gemzar and Hydrea, for antisense therapy, and in combination chemotherapies. Surprisingly, few novel drugs that target RNR have emerged, partly because RNR activity assays are laboratory-intense and exclude high-throughput methodologies. Here, we present a previously undescribed PCR-based assay for RNR activity measurements in microplate format. We validated the approach by screening a diverse library of 1,364 compounds for inhibitors of class I RNR from the opportunistic pathogen Pseudomonas aeruginosa, and we identified 27 inhibitors with IC(50) values from ∼200 nM to 30 μM. Interestingly, a majority of the identified inhibitors have been found inactive in human cell lines as well as in anticancer and in vivo tumor tests as reported by the PubChem BioAssay database. Four of the RNR inhibitors inhibited growth of P. aeruginosa, and two were also found to affect the transcription of RNR genes and to decrease the cellular deoxyribonucleotide pools. This unique PCR-based assay works with any RNR enzyme and any substrate nucleotide, and thus opens the door to high-throughput screening for RNR inhibitors in drug discovery.
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Affiliation(s)
- Fredrik Tholander
- Department of Biochemistry and Biophysics, Stockholm University, SE-106 91 Stockholm, Sweden; and
- Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, SE-171 77 Stockholm, Sweden
| | - Britt-Marie Sjöberg
- Department of Biochemistry and Biophysics, Stockholm University, SE-106 91 Stockholm, Sweden; and
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4
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Öhrström M, Popović-Bijelić A, Luo J, Stenmark P, Högbom M, Gräslund A. Inhibition of chlamydial class Ic ribonucleotide reductase by C-terminal peptides from protein R2. J Pept Sci 2011; 17:756-62. [DOI: 10.1002/psc.1399] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2011] [Revised: 06/16/2011] [Accepted: 06/27/2011] [Indexed: 12/14/2022]
Affiliation(s)
- Maria Öhrström
- Department of Biochemistry and Biophysics; Stockholm University; SE-10691 ; Stockholm; Sweden
| | - Ana Popović-Bijelić
- Department of Biochemistry and Biophysics; Stockholm University; SE-10691 ; Stockholm; Sweden
| | - Jinghui Luo
- Department of Biochemistry and Biophysics; Stockholm University; SE-10691 ; Stockholm; Sweden
| | - Pål Stenmark
- Department of Biochemistry and Biophysics; Stockholm University; SE-10691 ; Stockholm; Sweden
| | - Martin Högbom
- Department of Biochemistry and Biophysics; Stockholm University; SE-10691 ; Stockholm; Sweden
| | - Astrid Gräslund
- Department of Biochemistry and Biophysics; Stockholm University; SE-10691 ; Stockholm; Sweden
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5
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Gammon DB, Gowrishankar B, Duraffour S, Andrei G, Upton C, Evans DH. Vaccinia virus-encoded ribonucleotide reductase subunits are differentially required for replication and pathogenesis. PLoS Pathog 2010; 6:e1000984. [PMID: 20628573 PMCID: PMC2900304 DOI: 10.1371/journal.ppat.1000984] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2009] [Accepted: 06/03/2010] [Indexed: 11/19/2022] Open
Abstract
Ribonucleotide reductases (RRs) are evolutionarily-conserved enzymes that catalyze the rate-limiting step during dNTP synthesis in mammals. RR consists of both large (R1) and small (R2) subunits, which are both required for catalysis by the R12R22 heterotetrameric complex. Poxviruses also encode RR proteins, but while the Orthopoxviruses infecting humans [e.g. vaccinia (VACV), variola, cowpox, and monkeypox viruses] encode both R1 and R2 subunits, the vast majority of Chordopoxviruses encode only R2 subunits. Using plaque morphology, growth curve, and mouse model studies, we investigated the requirement of VACV R1 (I4) and R2 (F4) subunits for replication and pathogenesis using a panel of mutant viruses in which one or more viral RR genes had been inactivated. Surprisingly, VACV F4, but not I4, was required for efficient replication in culture and virulence in mice. The growth defects of VACV strains lacking F4 could be complemented by genes encoding other Chordopoxvirus R2 subunits, suggesting conservation of function between poxvirus R2 proteins. Expression of F4 proteins encoding a point mutation predicted to inactivate RR activity but still allow for interaction with R1 subunits, caused a dominant negative phenotype in growth experiments in the presence or absence of I4. Co-immunoprecipitation studies showed that F4 (as well as other Chordopoxvirus R2 subunits) form hybrid complexes with cellular R1 subunits. Mutant F4 proteins that are unable to interact with host R1 subunits failed to rescue the replication defect of strains lacking F4, suggesting that F4-host R1 complex formation is critical for VACV replication. Our results suggest that poxvirus R2 subunits form functional complexes with host R1 subunits to provide sufficient dNTPs for viral replication. Our results also suggest that R2-deficient poxviruses may be selective oncolytic agents and our bioinformatic analyses provide insights into how poxvirus nucleotide metabolism proteins may have influenced the base composition of these pathogens. Efficient genome replication is central to the virulence of all DNA viruses, including poxviruses. To ensure replication efficiency, many of the more virulent poxviruses encode their own nucleotide metabolism machinery, including ribonucleotide reductase (RR) enzymes, which act to provide ample DNA precursors for replication. RR enzymes require both large (R1) and small (R2) subunit proteins for activity. Curiously, some poxviruses only encode R2 subunits. Other poxviruses, such as the smallpox vaccine strain, vaccinia virus (VACV), encode both R1 and R2 subunits. We report here that the R2, but not the R1, subunit of VACV RR is required for efficient replication and virulence. We also provide evidence that several poxvirus R2 proteins form novel complexes with host R1 subunits and this interaction is required for efficient VACV replication in primate cells. Our study explains why some poxviruses only encode R2 subunits and identifies a role for these proteins in poxvirus pathogenesis. Furthermore, we provide evidence that mutant poxviruses unable to generate R2 proteins may become entirely dependent upon host RR activity. This may restrict their replication to cells that over-express RR proteins such as cancer cells, making them potential therapeutics for human malignancies.
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Affiliation(s)
- Don B. Gammon
- Department of Medical Microbiology and Immunology, University of Alberta, Edmonton, Alberta, Canada
| | - Branawan Gowrishankar
- Department of Medical Microbiology and Immunology, University of Alberta, Edmonton, Alberta, Canada
| | - Sophie Duraffour
- Laboratory of Virology and Rega Institute for Medical Research, Katholieke Universiteit Leuven, Leuven, Belgium
| | - Graciela Andrei
- Laboratory of Virology and Rega Institute for Medical Research, Katholieke Universiteit Leuven, Leuven, Belgium
| | - Chris Upton
- Biochemistry and Microbiology, University of Victoria, Victoria, British Columbia, Canada
| | - David H. Evans
- Department of Medical Microbiology and Immunology, University of Alberta, Edmonton, Alberta, Canada
- * E-mail:
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Popović-Bijelić A, Voevodskaya N, Domkin V, Thelander L, Gräslund A. Metal Binding and Activity of Ribonucleotide Reductase Protein R2 Mutants: Conditions for Formation of the Mixed Manganese−Iron Cofactor. Biochemistry 2009; 48:6532-9. [DOI: 10.1021/bi900693s] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Ana Popović-Bijelić
- Department of Biochemistry and Biophysics, Stockholm University, S-10691 Stockholm, Sweden
| | - Nina Voevodskaya
- Department of Biochemistry and Biophysics, Stockholm University, S-10691 Stockholm, Sweden
| | - Vladimir Domkin
- Department of Medical Biochemistry and Biophysics, Umeå University, S-90187 Umeå, Sweden
| | - Lars Thelander
- Department of Medical Biochemistry and Biophysics, Umeå University, S-90187 Umeå, Sweden
| | - Astrid Gräslund
- Department of Biochemistry and Biophysics, Stockholm University, S-10691 Stockholm, Sweden
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7
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Hassan AQ, Wang Y, Plate L, Stubbe J. Methodology to probe subunit interactions in ribonucleotide reductases. Biochemistry 2009; 47:13046-55. [PMID: 19012414 DOI: 10.1021/bi8012559] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Ribonucleotide reductases (RNRs) catalyze the conversion of nucleotides to deoxynucleotides, providing the monomeric precursors required for DNA replication and repair. Escherichia coli RNR is a 1:1 complex of two homodimeric subunits, alpha2 and beta2. The interactions between alpha2 and beta2 are thought to be largely associated with the C-terminal 20 amino acids (residues 356-375) of beta2. To study subunit interactions, a single reactive cysteine has been introduced into each of 15 positions along the C-terminal tail of beta2. Each cysteine has been modified with the photo-cross-linker benzophenone (BP) and the environmentally sensitive fluorophore dimethylaminonaphthalene (DAN). Each construct has been purified to homogeneity and characterized by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and electrospray ionization mass spectrometry (ESI-MS). Each BP-beta2 has been incubated with 1 equiv of alpha2 and photolyzed, and the results have been analyzed quantitatively by SDS-PAGE. Each DAN-beta2 was incubated with a 50-fold excess of alpha2, and the emission maximum and intensity were measured. A comparison of the results from the two sets of probes reveals that sites with the most extensive cross-linking are also associated with the greatest changes in fluorescence. Titration of four different DAN-beta2 variants (351, 356, 365, and 367) with alpha2 gave a K(d) approximately 0.4 microM for subunit interaction. Disruption of the interaction of the alpha2-DAN-beta2 complex is accompanied by a decrease in fluorescence intensity and can serve as a high-throughput screen for inhibitors of subunit interactions.
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Affiliation(s)
- A Quamrul Hassan
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
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8
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Hassan AQ, Stubbe J. Mapping the subunit interface of ribonucleotide reductase (RNR) using photo cross-linking. Bioorg Med Chem Lett 2008; 18:5923-5. [PMID: 18762419 PMCID: PMC2602823 DOI: 10.1016/j.bmcl.2008.08.048] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2008] [Revised: 08/03/2008] [Accepted: 08/05/2008] [Indexed: 10/21/2022]
Abstract
Escherichia coli ribonucleotide reductase (RNR) catalyzes the conversion of nucleoside 5'-diphosphates to deoxynucleoside 5'-diphosphates and is a 1:1 complex of two homodimeric subunits: alpha2 and beta2. As a first step towards mapping the subunit interface, beta2 (V365C) was labeled with [(14)C]-benzophenone (BP) iodoacetamide. The resulting [(14)C]-BP-beta2 (V365C) was complexed with alpha2 and irradiated at 365nm for 30min at 4 degrees C. The cross-linked mixture was purified by anion exchange chromatography and digested with trypsin. The peptides were purified by reverse phase chromatography, identified by scintillation counting and analyzed by Edman sequencing. Three [(14)C]-labeled peptides were identified: two contained a peptide in beta to which the BP was attached. The third contained the same beta peptide and a peptide in alpha found in its alphaD helix. These results provide direct support for the proposed docking model of alpha2beta2.
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Affiliation(s)
- A Quamrul Hassan
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge MA 02139
| | - JoAnne Stubbe
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge MA 02139
- Department of Biology, Massachusetts Institute of Technology, Cambridge MA 02139
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9
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Wnuk SF, Robins MJ. Ribonucleotide reductase inhibitors as anti-herpes agents. Antiviral Res 2006; 71:122-6. [PMID: 16621038 DOI: 10.1016/j.antiviral.2006.03.002] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2006] [Revised: 03/09/2006] [Accepted: 03/09/2006] [Indexed: 11/20/2022]
Abstract
Ribonucleotide reductases (RNRs) supply the 2'-deoxyribonucleotide building blocks for DNA synthesis in mammalian cells and for herpes viruses. The viral-encoded RNRs have unique protein sequences that differ from mammalian enzyme primary structures. Selective inhibition of a viral RNR might provide an approach to new anti-herpes agents with minimal effects on the mammalian host RNRs. This review summarizes efforts to develop anti-herpes agents that selectively target viral-encoded RNRs.
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Affiliation(s)
- Stanislaw F Wnuk
- Department of Chemistry, Florida International University, University Park, Miami, FL 33199, United States
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10
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Shao J, Zhou B, Di Bilio AJ, Zhu L, Wang T, Qi C, Shih J, Yen Y. A Ferrous-triapine complex mediates formation of reactive oxygen species that inactivate human ribonucleotide reductase. Mol Cancer Ther 2006; 5:586-92. [PMID: 16546972 DOI: 10.1158/1535-7163.mct-05-0384] [Citation(s) in RCA: 130] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Ribonucleotide reductase plays a central role in cell proliferation by supplying deoxyribonucleotide precursors for DNA synthesis and repair. The holoenzyme is a protein tetramer that features two large (hRRM1) and two small (hRRM2 or p53R2) subunits. The small subunit contains a di-iron cluster/tyrosyl radical cofactor that is essential for enzyme activity. Triapine (3-aminopyridine-2-carboxaldehyde thiosemicarbazone, 3-AP) is a new, potent ribonucleotide reductase inhibitor currently in phase II clinical trials for cancer chemotherapy. Ferric chloride readily reacts with Triapine to form an Fe(III)-(3-AP) complex, which is reduced to Fe(II)-(3-AP) by DTT. Spin-trapping experiments with 5,5-dimethyl-1-pyrroline-N-oxide prove that Fe(II)-(3-AP) reduces O2 to give oxygen reactive species (ROS). In vitro activity assays show that Fe(II)-(3-AP) is a much more potent inhibitor of hRRM2/hRRM1 and p53R2/hRRM1 than Triapine. Electron paramagnetic resonance measurements on frozen solutions of hRRM2 and p53R2 show that their tyrosyl radicals are completely quenched by incubation with Fe(II)-(3-AP). However, the enzyme activity is maintained in protein samples supplemented with catalase alone or in combination with superoxide dismutase. Furthermore, catalase alone or in combination with superoxide dismutase markedly decreases the antiproliferative effect of Triapine in cytotoxicity assays. These results indicate that Triapine-induced inhibition of ribonucleotide reductase is caused by ROS. We suggest that ROS may ultimately be responsible for the pharmacologic effects of Triapine in vivo.
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Affiliation(s)
- Jimin Shao
- Department of Medical Oncology and Therapeutic Research, City of Hope National Medical Center, 1500 East Duarte Road, Duarte, CA 91010, USA
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11
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Yen Y, Chu B, Yen C, Shih J, Zhou B. Enzymatic property analysis of p53R2 subunit of human ribonucleotide reductase. ACTA ACUST UNITED AC 2006; 46:235-47. [PMID: 16846634 DOI: 10.1016/j.advenzreg.2006.01.016] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Affiliation(s)
- Yun Yen
- Department of Medical Oncology and Therapeutic, City of Hope National Medical Center, 1500 E. Duarte Road, Duarte, CA 91010, USA.
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12
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Gao Y, Kashlan OB, Kaur J, Tan C, Cooperman BS. Mechanisms of action of peptide inhibitors of mammalian ribonucleotide reductase targeting quaternary structure. Biopolymers 2005; 80:9-17. [PMID: 15586357 DOI: 10.1002/bip.20184] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Mammalian ribonucleotide reductase (mRR) is a chemotherapeutic target. The enzyme is composed of 2 subunits (mR1 and mR2) and is inhibited by Ac-FTLDADF (denoted P7), corresponding to the C-terminus of mR2, which competes with mR2 for binding to mR1. mRR has 2 physiologically important active forms, mR12mR22 and mR16(mR22)j (j = 1-3). Here we report on the mechanism of action of recently identified peptide derivatives having higher activities than P7 toward inhibition of one or both active forms. A significant feature of both P7 and these new inhibitors is that they are more potent vs. mR12mR22 than mR16(mR22)j. For some of these peptides, this is due in part to their preferential binding to the mR1 monomer. The possible application of these peptide derivatives in cancer chemotherapy is discussed.
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Affiliation(s)
- Ying Gao
- Department of Chemistry, University of Pennsylvania, Philadelphia, PA 19104-6323, USA
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13
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Formaggio F, Baldini C, Moretto V, Crisma M, Kaptein B, Broxterman QB, Toniolo C. Preferred Conformations of Peptides Containingtert-Leucine, a Sterically Demanding, Lipophilic ?-Amino Acid with a Quaternary Side-Chain C? Atom. Chemistry 2005; 11:2395-404. [PMID: 15669065 DOI: 10.1002/chem.200400892] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Terminally protected homopeptides of tert-leucine, from the dimer to the hexamer, co-oligopeptides of tert-leucine in combination with alpha-aminoisobutyric acid or glycine residues up to the hexamer level, and simple dipeptides representing known scaffolds for catalysts in asymmetric organic reactions were prepared by solution methods and fully characterized. The results of conformation analysis, performed by use of FT-IR absorption, NMR, CD, and X-ray diffraction techniques, indicate that this hydrophobic alpha-amino acid with tetrasubstitution at the Cbeta atom is structurally versatile. We show that it prefers extended or semiextended conformations, but can also be accommodated in folded structures, provided that these are biased by the presence of helicogenic residues. The current large-scale production of Tle, combined with its conformational preferences unravelled in this work, should make this bulky, hydrophobic, Calpha-trisubstituted alpha-amino acid a regular building block of any strategy seeking to tailor peptides with improved catalytic and pharmacological properties.
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Affiliation(s)
- Fernando Formaggio
- Institute of Biomolecular Chemistry, CNR, and Department of Chemistry, University of Padova, via Marzolo 1, 35131 Padova, Italy.
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14
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Shao J, Zhou B, Zhu L, Qiu W, Yuan YC, Xi B, Yen Y. In vitro characterization of enzymatic properties and inhibition of the p53R2 subunit of human ribonucleotide reductase. Cancer Res 2004; 64:1-6. [PMID: 14729598 DOI: 10.1158/0008-5472.can-03-3048] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
p53R2 is a newly identified subunit of ribonucleotide reductase (RR) and plays a crucial role in supplying precursors for DNA repair in a p53-dependent manner. In our current work, all three human RR subunit proteins (p53R2, hRRM2, and hRRM1) were prokaryotically expressed and highly purified. Using an in vitro [(3)H]CDP reduction assay, the activity of RR reconstituted with either p53R2 or hRRM2 was found to be time, concentration, and hRRM1 dependent. The kinetic activity of p53R2-containing RR was about 20-50% lower than that of hRRM2-containing RR. Using a synthetic heptapeptide to inhibit RR activity, it was shown that p53R2 bound to hRRM1 through the same COOH-terminal heptapeptide as hRRM2. However, hRRM2 had a 4.76-fold higher binding affinity for hRRM1 than p53R2, which may explain the reduced RR activity of p53R2 relative to hRRM2. Of interest, p53R2 was 158-fold more susceptible to the iron chelator deferoxamine mesylate than hRRM2, although the iron content of the two proteins determined by atomic absorption spectrometer was almost the same. To the contrary, p53R2 was 2.50-fold less sensitive than hRRM2 to the radical scavenger hydroxyurea, whereas EPR showed similar spectra of the tyrosyl radical in two proteins. Triapine, a new RR inhibitor, was equally potent for p53R2 and hRRM2. These inhibition studies showed that the iron center and tyrosyl radical are involved in RR activity for both p53R2 and hRRM2. The susceptibility differences to RR inhibitors between p53R2 and hRRM2 may lead to a new direction in drug design for human cancer treatment.
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Affiliation(s)
- Jimin Shao
- Departments of Medical Oncology and Therapeutic Research and Bioinformatics, City of Hope National Medical Center, Duarte, California 91010, USA
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