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Nakashima K, Georgiev A, Yordanov D, Matsushima Y, Hirashima SI, Miura T, Antonov L. Solvent-Triggered Long-Range Proton Transport in 7-Hydroxyquinoline Using a Sulfonamide Transporter Group. J Org Chem 2022; 87:6794-6806. [PMID: 35512011 DOI: 10.1021/acs.joc.2c00494] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
The ability of long-range proton transport by substitution of 7-hydroxyquinoline at the eighth position with sulfonamide and sulfonylhydrazone rotor units to act as a crane-arm has been studied. Different proton transport pathways triggered by different stimuli have been established depending on the structure of the crane-arms. Solvent-driven proton switching from OH to the quinoline nitrogen (Nquin) site, facilitated by a sulfonamide transporter group in polar protic and aprotic solvents, has been confirmed by optical (absorption and fluorescence) and NMR spectroscopies as well as by single-crystal X-ray structure analysis. Photoinduced long-range proton transport to the Nquin site upon 340 nm UV light irradiation has been estimated in sulfonylhydrazone, which is not sensitive to solvent-driven switching. Both compounds have exhibited acid-triggered switching by trifluoroacetic acid due to the formation of a stable six-membered intramolecular hydrogen bonding interaction between the protonated Nquin and crane-arm. The structures of acid-switched form were confirmed by NMR spectroscopy and single-crystal X-ray structure analysis. The behavior of the compounds suggests a big step forward in the advanced proton pump-switching architecture because they cover three distinct driving forces in the switching process: solvent, light, and acid.
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Affiliation(s)
- Kosuke Nakashima
- Department of Pharmaceutical Chemistry, Tokyo University of Pharmacy and Life Sciences, 1432-1 Horinouchi, Hachioji, Tokyo 192-0392, Japan
| | - Anton Georgiev
- Department of Organic Chemistry, University of Chemical Technology and Metallurgy, 8 St. Kliment Ohridski Boulevard, 1756 Sofia, Bulgaria.,Institute of Electronics, Bulgarian Academy of Sciences, 72 Tzarigradsko Chaussee Boulevard, 1784 Sofia, Bulgaria.,Institute of Optical Materials and Technologies, Bulgarian Academy of Sciences, Acad. G. Bonchev Avenue, Building 109, 1113 Sofia, Bulgaria
| | - Dancho Yordanov
- Institute of Electronics, Bulgarian Academy of Sciences, 72 Tzarigradsko Chaussee Boulevard, 1784 Sofia, Bulgaria.,Institute of Organic Chemistry with Centre of Phytochemistry, Bulgarian Academy of Sciences, Acad. G. Bonchev Avenue, Building 9, Sofia 1113, Bulgaria
| | - Yasuyuki Matsushima
- Department of Pharmaceutical Chemistry, Tokyo University of Pharmacy and Life Sciences, 1432-1 Horinouchi, Hachioji, Tokyo 192-0392, Japan
| | - Shin-Ichi Hirashima
- Department of Pharmaceutical Chemistry, Tokyo University of Pharmacy and Life Sciences, 1432-1 Horinouchi, Hachioji, Tokyo 192-0392, Japan
| | - Tsuyoshi Miura
- Department of Pharmaceutical Chemistry, Tokyo University of Pharmacy and Life Sciences, 1432-1 Horinouchi, Hachioji, Tokyo 192-0392, Japan
| | - Liudmil Antonov
- Department of Organic Chemistry, University of Chemical Technology and Metallurgy, 8 St. Kliment Ohridski Boulevard, 1756 Sofia, Bulgaria.,Institute of Electronics, Bulgarian Academy of Sciences, 72 Tzarigradsko Chaussee Boulevard, 1784 Sofia, Bulgaria
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2
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Fast E/Z UV-light response T-type photoswitching of phenylene-thienyl imines. J Photochem Photobiol A Chem 2022. [DOI: 10.1016/j.jphotochem.2022.113994] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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3
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Dangerfield TL, Kirmizialtin S, Johnson KA. Conformational dynamics during misincorporation and mismatch extension defined using a DNA polymerase with a fluorescent artificial amino acid. J Biol Chem 2021; 298:101451. [PMID: 34838820 PMCID: PMC8715121 DOI: 10.1016/j.jbc.2021.101451] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2021] [Revised: 09/09/2021] [Accepted: 11/23/2021] [Indexed: 11/29/2022] Open
Abstract
High-fidelity DNA polymerases select the correct nucleotide over the structurally similar incorrect nucleotides with extremely high specificity while maintaining fast rates of incorporation. Previous analysis revealed the conformational dynamics and complete kinetic pathway governing correct nucleotide incorporation using a high-fidelity DNA polymerase variant containing a fluorescent unnatural amino acid. Here we extend this analysis to investigate the kinetics of nucleotide misincorporation and mismatch extension. We report the specificity constants for all possible misincorporations and characterize the conformational dynamics of the enzyme during misincorporation and mismatch extension. We present free energy profiles based on the kinetic measurements and discuss the effect of different steps on specificity. During mismatch incorporation and subsequent extension with the correct nucleotide, the rates of the conformational change and chemistry are both greatly reduced. The nucleotide dissociation rate, however, increases to exceed the rate of chemistry. To investigate the structural basis for discrimination against mismatched nucleotides, we performed all atom molecular dynamics simulations on complexes with either the correct or mismatched nucleotide bound at the polymerase active site. The simulations suggest that the closed form of the enzyme with a mismatch bound is greatly destabilized due to weaker interactions with active site residues, nonideal base pairing, and a large increase in the distance from the 3'-OH group of the primer strand to the α-phosphate of the incoming nucleotide, explaining the reduced rates of misincorporation. The observed kinetic and structural mechanisms governing nucleotide misincorporation reveal the general principles likely applicable to other high-fidelity DNA polymerases.
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Affiliation(s)
- Tyler L Dangerfield
- Department of Molecular Biosciences, Institute for Cellular and Molecular Biology, University of Texas, Austin, Texas, USA
| | - Serdal Kirmizialtin
- Chemistry Program, Division of Science, New York University Abu Dhabi, Abu Dhabi, United Arab Emirates
| | - Kenneth A Johnson
- Department of Molecular Biosciences, Institute for Cellular and Molecular Biology, University of Texas, Austin, Texas, USA.
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4
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Vyas R, Reed AJ, Raper AT, Zahurancik WJ, Wallenmeyer PC, Suo Z. Structural basis for the D-stereoselectivity of human DNA polymerase β. Nucleic Acids Res 2017; 45:6228-6237. [PMID: 28402499 PMCID: PMC5449621 DOI: 10.1093/nar/gkx252] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2016] [Revised: 03/24/2017] [Accepted: 04/03/2017] [Indexed: 12/20/2022] Open
Abstract
Nucleoside reverse transcriptase inhibitors (NRTIs) with L-stereochemistry have long been an effective treatment for viral infections because of the strong D-stereoselectivity exhibited by human DNA polymerases relative to viral reverse transcriptases. The D-stereoselectivity of DNA polymerases has only recently been explored structurally and all three DNA polymerases studied to date have demonstrated unique stereochemical selection mechanisms. Here, we have solved structures of human DNA polymerase β (hPolβ), in complex with single-nucleotide gapped DNA and L-nucleotides and performed pre-steady-state kinetic analysis to determine the D-stereoselectivity mechanism of hPolβ. Beyond a similar 180° rotation of the L-nucleotide ribose ring seen in other studies, the pre-catalytic ternary crystal structures of hPolβ, DNA and L-dCTP or the triphosphate forms of antiviral drugs lamivudine ((-)3TC-TP) and emtricitabine ((-)FTC-TP) provide little structural evidence to suggest that hPolβ follows the previously characterized mechanisms of D-stereoselectivity. Instead, hPolβ discriminates against L-stereochemistry through accumulation of several active site rearrangements that lead to a decreased nucleotide binding affinity and incorporation rate. The two NRTIs escape some of the active site selection through the base and sugar modifications but are selected against through the inability of hPolβ to complete thumb domain closure.
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Affiliation(s)
- Rajan Vyas
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH 43210, USA
| | - Andrew J. Reed
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH 43210, USA
- The Ohio State Biochemistry Program, The Ohio State University, Columbus, OH 43210, USA
| | - Austin T. Raper
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH 43210, USA
- The Ohio State Biochemistry Program, The Ohio State University, Columbus, OH 43210, USA
| | - Walter J. Zahurancik
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH 43210, USA
- The Ohio State Biochemistry Program, The Ohio State University, Columbus, OH 43210, USA
| | - Petra C. Wallenmeyer
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH 43210, USA
| | - Zucai Suo
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH 43210, USA
- The Ohio State Biochemistry Program, The Ohio State University, Columbus, OH 43210, USA
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5
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Liu K, Zang Y, Guo X, Wei F, Yin J, Pang L, Chen D. The Δ133p53 Isoform Reduces Wtp53-induced Stimulation of DNA Pol γ Activity in the Presence and Absence of D4T. Aging Dis 2017; 8:228-239. [PMID: 28400988 PMCID: PMC5362181 DOI: 10.14336/ad.2016.0910] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2016] [Accepted: 09/10/2016] [Indexed: 01/02/2023] Open
Abstract
The mitochondrial toxicity of nucleoside reverse transcriptase inhibitors (NRTIs) is due to the inhibition of mitochondrial DNA (mtDNA) polymerase γ (pol γ). Previous studies have shown that wild type p53 (wtp53) can interact with pol γ and mtDNA to enhance mitochondrial DNA base excision repair (mtBER) activity and increase the accuracy of DNA synthesis. The N-terminal transactivation domain and central specific DNA-binding domain of p53 play critical roles in the stimulation of BER. In this study, we identified the possible roles of wtp53, Δ40p53 and Δ133p53 in regulating mtDNA pol γ activity in cells with d4T treatment. The results show that Δ40p53 and Δ133p53 can exist in mitochondrial fragments and form polymers with themselves or wtp53. Unlike wtP53, Δ133p53 alone cannot increase DNA pol γ activity. More importantly, we found that Δ133p53 played a negative role in p53 stimulation of DNA pol γ activity when studied in d4T-treated and d4T-untreated mitochondrial extracts. Gel shift data also indicate that Δ40p53 and Δ133p53 cannot interact with APE. Wtp53 and Δ40p53 can act antagonize the effect of d4T inhibition of DNA pol γ activity. However, when wtp53 interacted with Δ133p53, DNA pol γ activity was significantly decreased. Conclusion: Δ133p53 negatively regulates p53’s stimulation of pol γ in the presence and absence of d4T.
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Affiliation(s)
- Kai Liu
- 1Beijing Institute of Hepatology, Beijing You An Hospital, Capital Medical University, Beijing 100069, China
| | - Yunjin Zang
- 2The Affiliated Hospital of Qingdao University, Organ Transplantation Center, Qingdao, Shandong 266003, China
| | - Xianghua Guo
- 1Beijing Institute of Hepatology, Beijing You An Hospital, Capital Medical University, Beijing 100069, China
| | - Feili Wei
- 1Beijing Institute of Hepatology, Beijing You An Hospital, Capital Medical University, Beijing 100069, China
| | - Jiming Yin
- 1Beijing Institute of Hepatology, Beijing You An Hospital, Capital Medical University, Beijing 100069, China
| | - Lijun Pang
- 1Beijing Institute of Hepatology, Beijing You An Hospital, Capital Medical University, Beijing 100069, China
| | - Dexi Chen
- 1Beijing Institute of Hepatology, Beijing You An Hospital, Capital Medical University, Beijing 100069, China
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6
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Gaur V, Vyas R, Fowler JD, Efthimiopoulos G, Feng JY, Suo Z. Structural and kinetic insights into binding and incorporation of L-nucleotide analogs by a Y-family DNA polymerase. Nucleic Acids Res 2014; 42:9984-95. [PMID: 25104018 PMCID: PMC4150803 DOI: 10.1093/nar/gku709] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Considering that all natural nucleotides (D-dNTPs) and the building blocks (D-dNMPs) of DNA chains possess D-stereochemistry, DNA polymerases and reverse transcriptases (RTs) likely possess strongD-stereoselectivity by preferably binding and incorporating D-dNTPs over unnatural L-dNTPs during DNA synthesis. Surprisingly, a structural basis for the discrimination against L-dNTPs by DNA polymerases or RTs has not been established although L-deoxycytidine analogs (lamivudine and emtricitabine) and L-thymidine (telbivudine) have been widely used as antiviral drugs for years. Here we report seven high-resolution ternary crystal structures of a prototype Y-family DNA polymerase, DNA, and D-dCTP, D-dCDP, L-dCDP, or the diphosphates and triphosphates of lamivudine and emtricitabine. These structures reveal that relative to D-dCTP, each of these L-nucleotides has its sugar ring rotated by 180° with an unusual O4'-endo sugar puckering and exhibits multiple triphosphate-binding conformations within the active site of the polymerase. Such rare binding modes significantly decrease the incorporation rates and efficiencies of these L-nucleotides catalyzed by the polymerase.
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Affiliation(s)
- Vineet Gaur
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH 43210, USA
| | - Rajan Vyas
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH 43210, USA
| | - Jason D Fowler
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH 43210, USA
| | - Georgia Efthimiopoulos
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH 43210, USA
| | - Joy Y Feng
- Gilead Sciences, Inc., 333 Lakeside Drive, Foster City, CA 94044, USA
| | - Zucai Suo
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH 43210, USA
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7
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Walsh JM, Beuning PJ. Synthetic nucleotides as probes of DNA polymerase specificity. J Nucleic Acids 2012; 2012:530963. [PMID: 22720133 PMCID: PMC3377560 DOI: 10.1155/2012/530963] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2012] [Accepted: 03/21/2012] [Indexed: 12/17/2022] Open
Abstract
The genetic code is continuously expanding with new nucleobases designed to suit specific research needs. These synthetic nucleotides are used to study DNA polymerase dynamics and specificity and may even inhibit DNA polymerase activity. The availability of an increasing chemical diversity of nucleotides allows questions of utilization by different DNA polymerases to be addressed. Much of the work in this area deals with the A family DNA polymerases, for example, Escherichia coli DNA polymerase I, which are DNA polymerases involved in replication and whose fidelity is relatively high, but more recent work includes other families of polymerases, including the Y family, whose members are known to be error prone. This paper focuses on the ability of DNA polymerases to utilize nonnatural nucleotides in DNA templates or as the incoming nucleoside triphosphates. Beyond the utility of nonnatural nucleotides as probes of DNA polymerase specificity, such entities can also provide insight into the functions of DNA polymerases when encountering DNA that is damaged by natural agents. Thus, synthetic nucleotides provide insight into how polymerases deal with nonnatural nucleotides as well as into the mutagenic potential of nonnatural nucleotides.
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Affiliation(s)
- Jason M. Walsh
- Department of Chemistry and Chemical Biology, Northeastern University, 360 Huntington Avenue, 102 Hurtig Hall, Boston, MA 02115, USA
| | - Penny J. Beuning
- Department of Chemistry and Chemical Biology, Northeastern University, 360 Huntington Avenue, 102 Hurtig Hall, Boston, MA 02115, USA
- Center for Interdisciplinary Research on Complex Systems, Northeastern University, Boston, MA 02115, USA
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8
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Xia S, Eom SH, Konigsberg WH, Wang J. Structural basis for differential insertion kinetics of dNMPs opposite a difluorotoluene nucleotide residue. Biochemistry 2012; 51:1476-85. [PMID: 22304682 DOI: 10.1021/bi2016487] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
We have recently challenged the widely held view that 2,4-difluorotoluene (dF) is a nonpolar isosteric analogue of the nucleotide dT, incapable of forming hydrogen bonds (HBs). To gain a further understanding for the kinetic preference that favors dAMP insertion opposite a templating dF, a result that mirrors the base selectivity that favors dAMP insertion opposite dT by RB69 DNA polymerase (RB69pol), we determined presteady-state kinetic parameters for incorporation of four dNMPs opposite dF by RB69pol and solved the structures of corresponding ternary complexes. We observed that both the F2 and F4 substituent of dF in these structures serve as HB acceptors forming HBs either directly with dTTP and dGTP or indirectly with dATP and dCTP via ordered water molecules. We have defined the shape and chemical features of each dF/dNTP pair in the RB69pol active site without the corresponding phosphodiester-linkage constraints of dF/dNs when they are embedded in isolated DNA duplexes. These features can explain the kinetic preferences exhibited by the templating dF when the nucleotide incorporation is catalyzed by wild type RB69pol or its mutants. We further show that the shapes of the dNTP/dF nascent base pair differ markedly from the corresponding dNTP/dT in the pol active site and that these differences have a profound effect on their incorporation efficiencies.
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Affiliation(s)
- Shuangluo Xia
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut 06520-8114, United States
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9
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Euro L, Farnum GA, Palin E, Suomalainen A, Kaguni LS. Clustering of Alpers disease mutations and catalytic defects in biochemical variants reveal new features of molecular mechanism of the human mitochondrial replicase, Pol γ. Nucleic Acids Res 2011; 39:9072-84. [PMID: 21824913 PMCID: PMC3241644 DOI: 10.1093/nar/gkr618] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Mutations in Pol γ represent a major cause of human mitochondrial diseases, especially those affecting the nervous system in adults and in children. Recessive mutations in Pol γ represent nearly half of those reported to date, and they are nearly uniformly distributed along the length of the POLG1 gene (Human DNA Polymerase gamma Mutation Database); the majority of them are linked to the most severe form of POLG syndrome, Alpers–Huttenlocher syndrome. In this report, we assess the structure–function relationships for recessive disease mutations by reviewing existing biochemical data on site-directed mutagenesis of the human, Drosophila and yeast Pol γs, and their homologs from the family A DNA polymerase group. We do so in the context of a molecular model of Pol γ in complex with primer–template DNA, which we have developed based upon the recently solved crystal structure of the apoenzyme form. We present evidence that recessive mutations cluster within five distinct functional modules in the catalytic core of Pol γ. Our results suggest that cluster prediction can be used as a diagnosis-supporting tool to evaluate the pathogenic role of new Pol γ variants.
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Affiliation(s)
- Liliya Euro
- Research Programs Unit, Molecular Neurology, Biomedicum-Helsinki, University of Helsinki, Haartmaninkatu 8, 00290 Helsinki, Finland
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10
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Ding H, Greenberg MM. DNA damage and interstrand cross-link formation upon irradiation of aryl iodide C-nucleotide analogues. J Org Chem 2010; 75:535-44. [PMID: 20067226 PMCID: PMC2813935 DOI: 10.1021/jo902071y] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
The 5-halopyrimidine nucleotides damage DNA upon UV-irradiation or exposure to gamma-radiolysis via the formation of the 2'-deoxyuridin-5-yl sigma-radical. The bromo and iodo derivatives of these molecules are useful tools for probing DNA structure and as therapeutically useful radiosensitizing agents. A series of aryl iodide C-nucleotides were incorporated into synthetic oligonucleotides and exposed to UV-irradiation and gamma-radiolysis. The strand damage produced upon irradiation of DNA containing these molecules is consistent with the generation of highly reactive sigma-radicals. Direct stand breaks and alkali-labile lesions are formed at the nucleotide analogue and flanking nucleotides. The distribution of lesion type and location varies depending upon the position of the aryl ring that is iodinated. Unlike 5-halopyrimidine nucleotides, the aryl iodides produce interstrand cross-links in duplex regions of DNA when exposed to gamma-radiolysis or UV-irradiation. Quenching studies suggest that cross-links are produced by gamma-radiolysis via capture of a solvated electron, and subsequent fragmentation to the sigma-radical. These observations suggest that aryl iodide C-nucleotide analogues may be useful as probes for excess electron transfer and radiosensitizing agents.
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Affiliation(s)
- Hui Ding
- Department of Chemistry, Johns Hopkins University, 3400 N. Charles Street, Baltimore, Maryland 21218, USA
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11
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Johnson KA. The kinetic and chemical mechanism of high-fidelity DNA polymerases. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2010; 1804:1041-8. [PMID: 20079883 DOI: 10.1016/j.bbapap.2010.01.006] [Citation(s) in RCA: 131] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/08/2009] [Revised: 12/15/2009] [Accepted: 01/04/2010] [Indexed: 10/19/2022]
Abstract
This review summarizes our current understanding of the structural, kinetic and thermodynamic basis for the extraordinary accuracy of high-fidelity DNA polymerases. High-fidelity DNA polymerases, such as the enzyme responsible for the replication of bacteriophage T7 DNA, discriminate against similar substrates with an accuracy that approaches one error in a million base pairs while copying DNA at a rate of approximately 300 base pairs per second. When the polymerase does make an error, it stalls, giving time for the slower proofreading exonuclease to remove the mismatch so that the overall error frequency approaches one in a billion. Structural analysis reveals a large change in conformation after nucleotide binding from an open to a closed state. Kinetic analysis has shown that the substrate-induced structural change plays a key role in the discrimination between correct and incorrect base pairs by governing whether a nucleotide will be retained and incorporated or rapidly released.
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Affiliation(s)
- Kenneth A Johnson
- Department of Chemistry and Biochemistry, Institute for Cellular and Molecular Biology, University of Texas, 2500 Speedway, Austin, TX 78712, USA.
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Affiliation(s)
- Michal Hocek
- Department of Chemistry, WestChem, University of Glasgow, Glasgow G12 8QQ, United Kingdom, and Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, Gilead & IOCB Research Center, CZ-16610 Prague 6, Czech Republic
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13
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Lee HR, Helquist SA, Kool ET, Johnson KA. Importance of hydrogen bonding for efficiency and specificity of the human mitochondrial DNA polymerase. J Biol Chem 2007; 283:14402-10. [PMID: 17650502 PMCID: PMC2386926 DOI: 10.1074/jbc.m705007200] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
To assess the contribution to discrimination afforded by base pair hydrogen bonding during DNA replication by the human mitochondrial DNA polymerase, we examined nucleoside mimics lacking hydrogen bond forming capability but retaining the overall steric shape of the natural nucleotide. We employed oligonucleotide templates containing either a deoxyadenosine shape mimic (dQ) or a deoxythymidine shape mimic (dF). Additionally, the nucleoside triphosphate analogs difluorotoluene deoxynucleoside triphosphate, 9-methyl-1-H-imidazo[(4,5)-b]pyridine deoxyribose triphosphate, and 4-methylbenzimidazole deoxyribose triphosphate (dZTP; another dATP shape mimic) were assayed. We used pre-steady state methods to determine the kinetic parameters governing nucleotide incorporation, k(pol) and K(d). In general, the loss of hydrogen bonding potential led to 2-3 kcal/mol reduction in ground state binding free energy, whereas effects on the maximum rate of polymerization were quite variable, ranging from negligible (dATP:dF) to nearly 4 kcal/mol (dZTP:dT). Although we observed only a 46-fold reduction in discrimination when dF was present in the template, there was a complete elimination of discrimination when dQ was present in the template. Our data with dF indicate that hydrogen bonding contributes 2.2 kcal/mol toward the efficiency of incorporation, whereas data with dQ (which may overestimate the effect due to poor steric mimicry) suggest a contribution of up to 6.8 kcal/mol. Taken together, the data suggest that sterics are necessary but not sufficient to achieve optimal efficiency and fidelity for DNA polymerase. Base pair hydrogen bonding contributes at least a third of the energy underlying nucleoside incorporation efficiency and specificity.
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Affiliation(s)
- Harold R Lee
- Department of Chemistry and Biochemistry, Institute of Cellular and Molecular Biology, University of Texas, Austin, TX 78712, USA
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