1
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Wang H, Ettedgui J, Forstater J, Robertson JWF, Reiner JE, Zhang H, Chen S, Kasianowicz JJ. Determining the Physical Properties of Molecules with Nanometer-Scale Pores. ACS Sens 2018; 3:251-263. [PMID: 29381331 DOI: 10.1021/acssensors.7b00680] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Nanometer-scale pores have been developed for the detection, characterization, and quantification of a wide range of analytes (e.g., ions, polymers, proteins, anthrax toxins, neurotransmitters, and synthetic nanoparticles) and for DNA sequencing. We describe the key requirements that made this method possible and how the technique evolved. Finally, we show that, despite sound theoretical work, which advanced both the conceptual framework and quantitative capability of the method, there are still unresolved questions that need to be addressed to further improve the technique.
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Affiliation(s)
- Haiyan Wang
- National Institute
of Standards and Technology Physical Measurement Laboratory, Gaithersburg, Maryland 20899, United States
- Shenzhen
Key Laboratory of Biomedical Engineering, School of Medicine, Shenzhen University, 3688 Nanhai Road, Shenzhen 508060, China
| | - Jessica Ettedgui
- National Institute
of Standards and Technology Physical Measurement Laboratory, Gaithersburg, Maryland 20899, United States
- Department
of Chemical Engineering, Columbia University New York, New York 10027, United States
| | - Jacob Forstater
- National Institute
of Standards and Technology Physical Measurement Laboratory, Gaithersburg, Maryland 20899, United States
- Department
of Chemical Engineering, Columbia University New York, New York 10027, United States
| | - Joseph W. F. Robertson
- National Institute
of Standards and Technology Physical Measurement Laboratory, Gaithersburg, Maryland 20899, United States
| | - Joseph E. Reiner
- Department
of Physics, Virginia Commonwealth University, Richmond, Virginia 23284, United States
| | - Huisheng Zhang
- Shenzhen
Key Laboratory of Biomedical Engineering, School of Medicine, Shenzhen University, 3688 Nanhai Road, Shenzhen 508060, China
| | - Siping Chen
- Shenzhen
Key Laboratory of Biomedical Engineering, School of Medicine, Shenzhen University, 3688 Nanhai Road, Shenzhen 508060, China
| | - John J. Kasianowicz
- National Institute
of Standards and Technology Physical Measurement Laboratory, Gaithersburg, Maryland 20899, United States
- Department
of Applied Physics Applied Mathematics, Columbia University New York, New York 10027, United States
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2
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Recent progress in dissecting molecular recognition by DNA polymerases with non-native substrates. Curr Opin Chem Biol 2017; 41:43-49. [PMID: 29096323 DOI: 10.1016/j.cbpa.2017.10.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2017] [Accepted: 10/05/2017] [Indexed: 11/22/2022]
Abstract
DNA polymerases must discriminate the correct Watson-Crick base pair-forming deoxynucleoside triphosphate (dNTP) substrate from three other dNTPs and additional triphosphates found in the cell. The rarity of misincorporations in vivo, then, belies the high tolerance for dNTP analogs observed in vitro. Advances over the last 10 years in single-molecule fluorescence and electronic detection of dNTP analog incorporation enable exploration of the mechanism and limits to base discrimination by DNA polymerases. Such studies reveal transient motions of DNA polymerase during substrate recognition and mutagenesis in the context of erroneous dNTP incorporation that can lead to evolution and genetic disease. Further improvements in time resolution and noise reduction of single-molecule studies will uncover deeper mechanistic understanding of this critical, first step in evolution.
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3
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Meli M, Sustarsic M, Craggs TD, Kapanidis AN, Colombo G. DNA Polymerase Conformational Dynamics and the Role of Fidelity-Conferring Residues: Insights from Computational Simulations. Front Mol Biosci 2016; 3:20. [PMID: 27303671 PMCID: PMC4882331 DOI: 10.3389/fmolb.2016.00020] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2016] [Accepted: 05/10/2016] [Indexed: 12/11/2022] Open
Abstract
Herein we investigate the molecular bases of DNA polymerase I conformational dynamics that underlie the replication fidelity of the enzyme. Such fidelity is determined by conformational changes that promote the rejection of incorrect nucleotides before the chemical ligation step. We report a comprehensive atomic resolution study of wild type and mutant enzymes in different bound states and starting from different crystal structures, using extensive molecular dynamics (MD) simulations that cover a total timespan of ~5 ms. The resulting trajectories are examined via a combination of novel methods of internal dynamics and energetics analysis, aimed to reveal the principal molecular determinants for the (de)stabilization of a certain conformational state. Our results show that the presence of fidelity-decreasing mutations or the binding of incorrect nucleotides in ternary complexes tend to favor transitions from closed toward open structures, passing through an ensemble of semi-closed intermediates. The latter ensemble includes the experimentally observed ajar conformation which, consistent with previous experimental observations, emerges as a molecular checkpoint for the selection of the correct nucleotide to incorporate. We discuss the implications of our results for the understanding of the relationships between the structure, dynamics, and function of DNA polymerase I at the atomistic level.
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Affiliation(s)
- Massimiliano Meli
- Computational Biochemistry Group, Istituto di Chimica del Riconoscimento Molecolare, National Research Council of Italy Milano, Italy
| | - Marko Sustarsic
- Clarendon Laboratory, Department of Physics, Biological Physics Research Group, University of Oxford Oxford, UK
| | - Timothy D Craggs
- Clarendon Laboratory, Department of Physics, Biological Physics Research Group, University of Oxford Oxford, UK
| | - Achillefs N Kapanidis
- Clarendon Laboratory, Department of Physics, Biological Physics Research Group, University of Oxford Oxford, UK
| | - Giorgio Colombo
- Computational Biochemistry Group, Istituto di Chimica del Riconoscimento Molecolare, National Research Council of Italy Milano, Italy
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4
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Dahl JM, Lieberman KR, Wang H. Modulation of DNA Polymerase Noncovalent Kinetic Transitions by Divalent Cations. J Biol Chem 2016; 291:6456-70. [PMID: 26797125 PMCID: PMC4813572 DOI: 10.1074/jbc.m115.701797] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2015] [Revised: 01/02/2016] [Indexed: 11/06/2022] Open
Abstract
Replicative DNA polymerases (DNAPs) require divalent metal cations for phosphodiester bond formation in the polymerase site and for hydrolytic editing in the exonuclease site. Me(2+) ions are intimate architectural components of each active site, where they are coordinated by a conserved set of amino acids and functional groups of the reaction substrates. Therefore Me(2+) ions can influence the noncovalent transitions that occur during each nucleotide addition cycle. Using a nanopore, transitions in individual Φ29 DNAP complexes are resolved with single-nucleotide spatial precision and sub-millisecond temporal resolution. We studied Mg(2+) and Mn(2+), which support catalysis, and Ca(2+), which supports deoxynucleoside triphosphate (dNTP) binding but not catalysis. We examined their effects on translocation, dNTP binding, and primer strand transfer between the polymerase and exonuclease sites. All three metals cause a concentration-dependent shift in the translocation equilibrium, predominantly by decreasing the forward translocation rate. Me(2+) also promotes an increase in the backward translocation rate that is dependent upon the primer terminal 3'-OH group. Me(2+) modulates the translocation rates but not their response to force, suggesting that Me(2+) does not affect the distance to the transition state of translocation. Absent Me(2+), the primer strand transfer pathway between the polymerase and exonuclease sites displays additional kinetic states not observed at >1 mm Me(2+). Complementary dNTP binding is affected by Me(2+) identity, with Ca(2+) affording the highest affinity, followed by Mn(2+), and then Mg(2+). Both Ca(2+) and Mn(2+) substantially decrease the dNTP dissociation rate relative to Mg(2+), while Ca(2+) also increases the dNTP association rate.
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Affiliation(s)
- Joseph M Dahl
- From the Departments of Biomolecular Engineering and
| | | | - Hongyun Wang
- Applied Mathematics and Statistics, University of California, Santa Cruz, California 95064
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5
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Pugliese KM, Gul OT, Choi Y, Olsen TJ, Sims PC, Collins PG, Weiss GA. Processive Incorporation of Deoxynucleoside Triphosphate Analogs by Single-Molecule DNA Polymerase I (Klenow Fragment) Nanocircuits. J Am Chem Soc 2015; 137:9587-94. [PMID: 26147714 DOI: 10.1021/jacs.5b02074] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
DNA polymerases exhibit a surprising tolerance for analogs of deoxyribonucleoside triphosphates (dNTPs), despite the enzymes' highly evolved mechanisms for the specific recognition and discrimination of native dNTPs. Here, individual DNA polymerase I Klenow fragment (KF) molecules were tethered to a single-walled carbon nanotube field-effect transistor (SWCNT-FET) to investigate accommodation of dNTP analogs with single-molecule resolution. Each base incorporation accompanied a change in current with its duration defined by τclosed. Under Vmax conditions, the average time of τclosed was similar for all analog and native dNTPs (0.2 to 0.4 ms), indicating no kinetic impact on this step due to analog structure. Accordingly, the average rates of dNTP analog incorporation were largely determined by durations with no change in current defined by τopen, which includes molecular recognition of the incoming dNTP. All α-thio-dNTPs were incorporated more slowly, at 40 to 65% of the rate for the corresponding native dNTPs. During polymerization with 6-Cl-2APTP, 2-thio-dTTP, or 2-thio-dCTP, the nanocircuit uncovered an alternative conformation represented by positive current excursions that does not occur with native dNTPs. A model consistent with these results invokes rotations by the enzyme's O-helix; this motion can test the stability of nascent base pairs using nonhydrophilic interactions and is allosterically coupled to charged residues near the site of SWCNT attachment. This model with two opposing O-helix motions differs from the previous report in which all current excursions were solely attributed to global enzyme closure and covalent-bond formation. The results suggest the enzyme applies a dynamic stability-checking mechanism for each nascent base pair.
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Affiliation(s)
- Kaitlin M Pugliese
- Departments of †Chemistry, §Physics and Astronomy, and ⊥Molecular Biology and Biochemistry, University of California, Irvine, California 92697, United States
| | - O Tolga Gul
- Departments of †Chemistry, §Physics and Astronomy, and ⊥Molecular Biology and Biochemistry, University of California, Irvine, California 92697, United States
| | - Yongki Choi
- Departments of †Chemistry, §Physics and Astronomy, and ⊥Molecular Biology and Biochemistry, University of California, Irvine, California 92697, United States
| | - Tivoli J Olsen
- Departments of †Chemistry, §Physics and Astronomy, and ⊥Molecular Biology and Biochemistry, University of California, Irvine, California 92697, United States
| | - Patrick C Sims
- Departments of †Chemistry, §Physics and Astronomy, and ⊥Molecular Biology and Biochemistry, University of California, Irvine, California 92697, United States
| | - Philip G Collins
- Departments of †Chemistry, §Physics and Astronomy, and ⊥Molecular Biology and Biochemistry, University of California, Irvine, California 92697, United States
| | - Gregory A Weiss
- Departments of †Chemistry, §Physics and Astronomy, and ⊥Molecular Biology and Biochemistry, University of California, Irvine, California 92697, United States
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6
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Dahl JM, Wang H, Lázaro JM, Salas M, Lieberman KR. Kinetic mechanisms governing stable ribonucleotide incorporation in individual DNA polymerase complexes. Biochemistry 2014; 53:8061-76. [PMID: 25478721 PMCID: PMC4283934 DOI: 10.1021/bi501216a] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Ribonucleoside triphosphates (rNTPs) are frequently incorporated during DNA synthesis by replicative DNA polymerases (DNAPs), and once incorporated are not efficiently edited by the DNAP exonucleolytic function. We examined the kinetic mechanisms that govern selection of complementary deoxyribonucleoside triphosphates (dNTPs) over complementary rNTPs and that govern the probability of a complementary ribonucleotide at the primer terminus escaping exonucleolytic editing and becoming stably incorporated. We studied the quantitative responses of individual Φ29 DNAP complexes to ribonucleotides using a kinetic framework, based on our prior work, in which transfer of the primer strand from the polymerase to exonuclease site occurs prior to translocation, and translocation precedes dNTP binding. We determined transition rates between the pre-translocation and post-translocation states, between the polymerase and exonuclease sites, and for dNTP or rNTP binding, with single-nucleotide spatial precision and submillisecond temporal resolution, from ionic current time traces recorded when individual DNAP complexes are held atop a nanopore in an electric field. The predominant response to the presence of a ribonucleotide in Φ29 DNAP complexes before and after covalent incorporation is significant destabilization, relative to the presence of a deoxyribonucleotide. This destabilization is manifested in the post-translocation state prior to incorporation as a substantially higher rNTP dissociation rate and manifested in the pre-translocation state after incorporation as rate increases for both primer strand transfer to the exonuclease site and the forward translocation, with the probability of editing not directly increased. In the post-translocation state, the primer terminal 2'-OH group also destabilizes dNTP binding.
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Affiliation(s)
- Joseph M Dahl
- Department of Biomolecular Engineering, ‡Department of Applied Mathematics and Statistics, and §Department of Computer Engineering, Baskin School of Engineering, University of California , Santa Cruz, California 95064, United States
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7
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Lieberman KR, Dahl JM, Wang H. Kinetic mechanism at the branchpoint between the DNA synthesis and editing pathways in individual DNA polymerase complexes. J Am Chem Soc 2014; 136:7117-31. [PMID: 24761828 PMCID: PMC4046759 DOI: 10.1021/ja5026408] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Exonucleolytic editing of incorrectly incorporated nucleotides by replicative DNA polymerases (DNAPs) plays an essential role in the fidelity of DNA replication. Editing requires that the primer strand of the DNA substrate be transferred between the DNAP polymerase and exonuclease sites, separated by a distance that is typically on the order of ~30 Å. Dynamic transitions between functional states can be quantified with single-nucleotide spatial precision and submillisecond temporal resolution from ionic current time traces recorded when individual DNAP complexes are held atop a nanoscale pore in an electric field. In this study, we have exploited this capability to determine the kinetic relationship between the translocation step and primer strand transfer between the polymerase and exonuclease sites in complexes formed between the replicative DNAP from bacteriophage Φ29 and DNA. We demonstrate that the pathway for primer strand transfer from the polymerase to exonuclease site initiates prior to the translocation step, while complexes are in the pre-translocation state. We developed a mathematical method to determine simultaneously the forward and reverse translocation rates and the rates of primer strand transfer in both directions between the polymerase and the exonuclease sites, and we have applied it to determine these rates for Φ29 DNAP complexes formed with a DNA substrate bearing a fully complementary primer-template duplex. This work provides a framework that will be extended to determine the kinetic mechanisms by which incorporation of noncomplementary nucleotides promotes primer strand transfer from the polymerase site to the exonuclease site.
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Affiliation(s)
- Kate R Lieberman
- Department of Biomolecular Engineering, ‡Department of Applied Mathematics and Statistics, Baskin School of Engineering, University of California , Santa Cruz, California 95064, United States
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8
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Hohlbein J, Aigrain L, Craggs TD, Bermek O, Potapova O, Shoolizadeh P, Grindley NDF, Joyce CM, Kapanidis AN. Conformational landscapes of DNA polymerase I and mutator derivatives establish fidelity checkpoints for nucleotide insertion. Nat Commun 2014; 4:2131. [PMID: 23831915 PMCID: PMC3715850 DOI: 10.1038/ncomms3131] [Citation(s) in RCA: 66] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2012] [Accepted: 06/11/2013] [Indexed: 01/04/2023] Open
Abstract
The fidelity of DNA polymerases depends on conformational changes that promote the rejection of incorrect nucleotides before phosphoryl transfer. Here, we combine single-molecule FRET with the use of DNA polymerase I and various fidelity mutants to highlight mechanisms by which active-site side chains influence the conformational transitions and free-energy landscape that underlie fidelity decisions in DNA synthesis. Ternary complexes of high fidelity derivatives with complementary dNTPs adopt mainly a fully closed conformation, whereas a conformation with a FRET value between those of open and closed is sparsely populated. This intermediate-FRET state, which we attribute to a partially closed conformation, is also predominant in ternary complexes with incorrect nucleotides and, strikingly, in most ternary complexes of low-fidelity derivatives for both correct and incorrect nucleotides. The mutator phenotype of the low-fidelity derivatives correlates well with reduced affinity for complementary dNTPs and highlights the partially closed conformation as a primary checkpoint for nucleotide selection. The fidelity of DNA polymerases depends on conformational changes that promote the rejection of incorrect nucleotides. Here, by using an intramolecular single-molecule FRET assay, the authors establish and characterize the partially closed conformation as a crucial fidelity checkpoint.
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Affiliation(s)
- Johannes Hohlbein
- Biological Physics Research Group, Department of Physics, Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU, UK
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9
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Dahl JM, Wang H, Lázaro JM, Salas M, Lieberman KR. Dynamics of translocation and substrate binding in individual complexes formed with active site mutants of {phi}29 DNA polymerase. J Biol Chem 2014; 289:6350-6361. [PMID: 24464581 DOI: 10.1074/jbc.m113.535666] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The Φ29 DNA polymerase (DNAP) is a processive B-family replicative DNAP. Fluctuations between the pre-translocation and post-translocation states can be quantified from ionic current traces, when individual Φ29 DNAP-DNA complexes are held atop a nanopore in an electric field. Based upon crystal structures of the Φ29 DNAP-DNA binary complex and the Φ29 DNAP-DNA-dNTP ternary complex, residues Tyr-226 and Tyr-390 in the polymerase active site were implicated in the structural basis of translocation. Here, we have examined the dynamics of translocation and substrate binding in complexes formed with the Y226F and Y390F mutants. The Y226F mutation diminished the forward and reverse rates of translocation, increased the affinity for dNTP in the post-translocation state by decreasing the dNTP dissociation rate, and increased the affinity for pyrophosphate in the pre-translocation state. The Y390F mutation significantly decreased the affinity for dNTP in the post-translocation state by decreasing the association rate ∼2-fold and increasing the dissociation rate ∼10-fold, implicating this as a mechanism by which this mutation impedes DNA synthesis. The Y390F dissociation rate increase is suppressed when complexes are examined in the presence of Mn(2+) rather than Mg(2+). The same effects of the Y226F or Y390F mutations were observed in the background of the D12A/D66A mutations, located in the exonuclease active site, ∼30 Å from the polymerase active site. Although translocation rates were unaffected in the D12A/D66A mutant, these exonuclease site mutations caused a decrease in the dNTP dissociation rate, suggesting that they perturb Φ29 DNAP interdomain architecture.
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Affiliation(s)
- Joseph M Dahl
- Department of Biomolecular Engineering, University of California, Santa Cruz, California 95064
| | - Hongyun Wang
- Department of Applied Mathematics and Statistics, University of California, Santa Cruz, California 95064.
| | - José M Lázaro
- Instituto de Biología Molecular "Eladio Viñuela" (CSIC), Centro de Biología Molecular "Severo Ochoa" (CSIC-UAM), Universidad Autónoma, Canto Blanco, 28049 Madrid, Spain
| | - Margarita Salas
- Instituto de Biología Molecular "Eladio Viñuela" (CSIC), Centro de Biología Molecular "Severo Ochoa" (CSIC-UAM), Universidad Autónoma, Canto Blanco, 28049 Madrid, Spain.
| | - Kate R Lieberman
- Department of Biomolecular Engineering, University of California, Santa Cruz, California 95064.
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10
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Bermek O, Grindley NDF, Joyce CM. Prechemistry nucleotide selection checkpoints in the reaction pathway of DNA polymerase I and roles of glu710 and tyr766. Biochemistry 2013; 52:6258-74. [PMID: 23937394 PMCID: PMC3770053 DOI: 10.1021/bi400837k] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
![]()
The accuracy of high-fidelity DNA
polymerases such as DNA polymerase
I (Klenow fragment) is governed by conformational changes early in
the reaction pathway that serve as fidelity checkpoints, identifying
inappropriate template–nucleotide pairings. The fingers-closing
transition (detected by a fluorescence resonance energy transfer-based
assay) is the unique outcome of binding a correct incoming nucleotide,
both complementary to the templating base and with a deoxyribose (rather
than ribose) sugar structure. Complexes with mispaired dNTPs or complementary
rNTPs are arrested at an earlier stage, corresponding to a partially
closed fingers conformation, in which weak binding of DNA and nucleotide
promote dissociation and resampling of the substrate pool. A 2-aminopurine
fluorescence probe on the DNA template provides further information
about the steps preceding fingers closing. A characteristic 2-aminopurine
signal is observed on binding a complementary nucleotide, regardless
of whether the sugar is deoxyribose or ribose. However, mispaired
dNTPs show entirely different behavior. Thus, a fidelity checkpoint
ahead of fingers closing is responsible for distinguishing complementary
from noncomplementary nucleotides and routing them toward different
outcomes. The E710A mutator polymerase has a defect in the early fidelity
checkpoint such that some complementary dNTPs are treated as if they
were mispaired. In the Y766A mutant, the early checkpoint functions
normally, but some correctly paired dNTPs do not efficiently undergo
fingers closing. Thus, both mutator alleles cause a blurring of the
distinction between correct and incorrect base pairs and result in
a larger fraction of errors passing through the prechemistry fidelity
checkpoints.
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Affiliation(s)
- Oya Bermek
- Department of Molecular Biophysics and Biochemistry, Yale University , New Haven, Connecticut 06520, United States
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11
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Lieberman KR, Dahl JM, Mai AH, Cox A, Akeson M, Wang H. Kinetic mechanism of translocation and dNTP binding in individual DNA polymerase complexes. J Am Chem Soc 2013; 135:9149-55. [PMID: 23705688 DOI: 10.1021/ja403640b] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Complexes formed between phi29 DNA polymerase (DNAP) and DNA fluctuate discretely between the pre-translocation and post-translocation states on the millisecond time scale. The translocation fluctuations can be observed in ionic current traces when individual complexes are captured atop the α-hemolysin nanopore in an electric field. The presence of complementary 2'-deoxynucleoside triphosphate (dNTP) shifts the equilibrium across the translocation step toward the post-translocation state. Here we have determined quantitatively the kinetic relationship between the phi29 DNAP translocation step and dNTP binding. We demonstrate that dNTP binds to phi29 DNAP-DNA complexes only after the transition from the pre-translocation state to the post-translocation state; dNTP binding rectifies the translocation but it does not directly drive the translocation. Based on the measured time traces of current amplitude, we developed a method for determining the forward and reverse translocation rates and the dNTP association and dissociation rates, individually at each dNTP concentration and each voltage. The translocation rates, and their response to force, match those determined for phi29 DNAP-DNA binary complexes and are unaffected by dNTP. The dNTP association and dissociation rates do not vary as a function of voltage, indicating that force does not distort the polymerase active site and that dNTP binding does not directly involve a displacement in the translocation direction. This combined experimental and theoretical approach and the results obtained provide a framework for separately evaluating the effects of biological variables on the translocation transitions and their effects on dNTP binding.
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Affiliation(s)
- Kate R Lieberman
- Department of Biomolecular Engineering, University of California, Santa Cruz, Baskin School of Engineering, 1156 High Street, MS: SOE2, Santa Cruz, California 95064, USA.
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12
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Wang H, Hurt N, Dunbar WB. Measuring and modeling the kinetics of individual DNA-DNA polymerase complexes on a nanopore. ACS NANO 2013; 7:3876-3886. [PMID: 23565679 PMCID: PMC3682681 DOI: 10.1021/nn401180j] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
The assembly of a DNA-DNA polymerase binary complex is the precursory step in genome replication, in which the enzyme binds to the 3' junction created when a primer binds to its complementary substrate. In this study, we use an active control method for observing the binding interaction between Klenow fragment (exo-) (KF) in the bulk-phase chamber above an α-hemolysin (α-HL) nanopore and a single DNA molecule tethered noncovalently in the nanopore. Specifically, the control method regulates the temporal availability of the primer-template DNA to KF binding and unbinding above the nanopore, on millisecond-to-second time scales. Our nanopore measurements support a model that incorporates two mutually exclusive binding states of KF to DNA at the primer-template junction site, termed "weakly bound" and "strongly bound" states. The composite binding affinity constant, the equilibrium constant between the weak and strong states, and the unbound-to-strong association rate are quantified from the data using derived modeling analysis. The results support that the strong state is in the nucleotide incorporation pathway, consistent with other nanopore assays. Surprisingly, the measured unbound-to-strong association process does not fit a model that admits binding of only free (unbound) KF to the tethered DNA but does fit an association rate that is proportional to the total (unbound and DNA-bound) KF concentration in the chamber above the nanopore. Our method provides a tool for measuring pre-equilibrium kinetics one molecule at a time, serially and for tens of thousands of single-molecule events, and can be used for other polynucleotide-binding enzymes.
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Affiliation(s)
- Hongyun Wang
- Department of Applied Mathematics and Statistics, University of California, Santa Cruz, 95064
| | - Nicholas Hurt
- Department of Chemistry and Biochemistry, University of California, Santa Cruz, 95064
| | - William B. Dunbar
- Department of Computer Engineering, University of California, Santa Cruz, 95064
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13
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Maitra RD, Kim J, Dunbar WB. Recent advances in nanopore sequencing. Electrophoresis 2012; 33:3418-28. [PMID: 23138639 PMCID: PMC3804109 DOI: 10.1002/elps.201200272] [Citation(s) in RCA: 122] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2012] [Revised: 06/29/2012] [Accepted: 07/09/2012] [Indexed: 11/05/2022]
Abstract
The prospect of nanopores as a next-generation sequencing platform has been a topic of growing interest and considerable government-sponsored research for more than a decade. Oxford Nanopore Technologies recently announced the first commercial nanopore sequencing devices, to be made available by the end of 2012, while other companies (Life, Roche, and IBM) are also pursuing nanopore sequencing approaches. In this paper, the state of the art in nanopore sequencing is reviewed, focusing on the most recent contributions that have or promise to have next-generation sequencing commercial potential. We consider also the scalability of the circuitry to support multichannel arrays of nanopores in future sequencing devices, which is critical to commercial viability.
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14
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Lieberman KR, Dahl JM, Mai AH, Akeson M, Wang H. Dynamics of the translocation step measured in individual DNA polymerase complexes. J Am Chem Soc 2012; 134:18816-23. [PMID: 23101437 DOI: 10.1021/ja3090302] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Complexes formed between the bacteriophage phi29 DNA polymerase (DNAP) and DNA fluctuate between the pre-translocation and post-translocation states on the millisecond time scale. These fluctuations can be directly observed with single-nucleotide precision in real-time ionic current traces when individual complexes are captured atop the α-hemolysin nanopore in an applied electric field. We recently quantified the equilibrium across the translocation step as a function of applied force (voltage), active-site proximal DNA sequences, and the binding of complementary dNTP. To gain insight into the mechanism of this step in the DNAP catalytic cycle, in this study, we have examined the stochastic dynamics of the translocation step. The survival probability of complexes in each of the two states decayed at a single exponential rate, indicating that the observed fluctuations are between two discrete states. We used a robust mathematical formulation based on the autocorrelation function to extract the forward and reverse rates of the transitions between the pre-translocation state and the post-translocation state from ionic current traces of captured phi29 DNAP-DNA binary complexes. We evaluated each transition rate as a function of applied voltage to examine the energy landscape of the phi29 DNAP translocation step. The analysis reveals that active-site proximal DNA sequences influence the depth of the pre-translocation and post-translocation state energy wells and affect the location of the transition state along the direction of the translocation.
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Affiliation(s)
- Kate R Lieberman
- Biomolecular Engineering, University of California, Santa Cruz, 95064, United States.
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Olasagasti F, Ruiz de Gordoa JC. Miniaturized technology for protein and nucleic acid point-of-care testing. Transl Res 2012; 160:332-45. [PMID: 22683416 PMCID: PMC7104926 DOI: 10.1016/j.trsl.2012.02.012] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/29/2011] [Revised: 02/22/2012] [Accepted: 02/24/2012] [Indexed: 01/26/2023]
Abstract
The field of point-of-care (POC) testing technology is developing quickly and producing instruments that are increasingly reliable, while their size is being gradually reduced. Proteins are a common target for POC analyses and the detection of protein markers typically involves immunoassays aimed at detecting different groups of proteins such as tumor markers, inflammation proteins, and cardiac markers; but other techniques can also be used to analyze plasma proteins. In the case of nucleic acids, hybridization and amplification strategies can be used to record electromagnetic or electric signals. These techniques allow for the identification of specific viral or bacterial infections as well as specific cancers. In this review, we consider some of the latest advances in the analysis of specific nucleic acid and protein biomarkers, taking into account their trend toward miniaturization and paying special attention to the technology that can be implemented in future applications, such as lab-on-a-chip instruments.
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Key Words
- poc, point-of-care
- lfi, lateral flow immunochromatography
- psa, prostate-specific antigen
- hcg, human chorionic gonadotropin
- tsh, thyroid-stimulating hormone
- seb, staphylococcal enterotixin b
- fret, förster resonance energy transfer
- mmp, matrix metalloproteinase 9
- bnp, b-type natriuretic peptide
- crp, c-reactive protein
- pdms, polydimethylsiloxane
- ig, immunoglobulin
- hb a1c, hemoglobin a1c
- ag, antigen
- ab, antibody
- tnfα, tumor necrosis factor α
- pct, procalcitonin
- il, interleukin
- pcr, polymerase chain reaction
- ca, cancer antigen
- cea, carcinoembryonic antigen
- nmp, nuclear matrix protein
- s100β, s100 calcium binding protein beta
- elisa, enzyme-linked immunosorbent assay
- vegf, vascular endothelial growth factor
- pmma, methyl methacrylate
- ctni, cardiac troponin i
- egf, epidermal growth factor
- ip, interferon-inducible
- mcp, monocyte chemoattractant protein
- timp-1, tissue inhibitor of matrix metalloproteinase-1
- rantes, regulated upon activation, normal t cell expressed and secreted
- mip-1 β, macrophage inflammatory protein-beta
- ctnt, cardiac troponin t
- hrp, horseradish peroxidase
- si-fet, silicon field-effect-transistor
- afp, alpha fetoprotein
- act, antichymotrypsin
- mia, magnetic immunoassay
- apc, allophycocyanin
- he4, human epididymis protein 4
- tmb, 3,3',5,5'-tetramethylbenzidine
- hp, hairpin
- lamp, loop-mediated isothermal amplification
- mrsa, methicillin resistant staphylococcus aureus
- fmdv, foot-and-mouth disease virus
- mμlamp, multiplex microfluidic lamp
- had, helicase-dependent amplification
- nasba, nucleic acid sequence based amplification
- lfm, lateral flow chromatography microarrays
- hsp, heat shock proteins
- spr, surface plasmon resonance
- mems, micro-electro-mechanical systems
- mimed, magnetic integrated microfluidic electrochemical detectors
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Affiliation(s)
- Felix Olasagasti
- Department of Biochemistry and Molecular Biology, Farmazia Fakultatea/Facultad de Farmacia, UPV-EHU, Gasteiz, Spain.
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16
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Xie ZH. [The fidelity mechanism of DNA synthesis]. YI CHUAN = HEREDITAS 2012; 34:679-86. [PMID: 22698738 DOI: 10.3724/sp.j.1005.2012.00679] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Accurate DNA synthesis is vital to maintain genome stability and ensure propagation of species. Synthetic errors have far reaching consequences. Therefore, DNA synthesis is remarkably accurate. The high fidelity is mainly achieved through three steps: ① nucleotide selection, which is based on hydrogen, base pair shape, or some other elements; ② 3'→5' exonuclease proofreading, which removes mis-incorporated nucleotides in cis or trans; ③ repair process, which could correct mismatched nucleotides escaping from proofreading, such as mismatch repair, excission repair, homologous recombination repair, and translesion DNA synthesis. Because all polymerases are suitable targets for anticancer or antiviral drugs, their fidelity is involved in drug resistance and side effects. Understanding the molecular basis of synthesis fidelity is of vital importance. In this review, the fidelity mechanisms of DNA synthesis will be discussed in detail. Furthermore, their application perspective was discussed.
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Affiliation(s)
- Zhao-Hui Xie
- Key University Laboratory of Biotechnology and Utilization of Bio-resource of Shandong, Department of Biology, Dezhou University, Dezhou 253023, China.
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17
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Markiewicz RP, Vrtis KB, Rueda D, Romano LJ. Single-molecule microscopy reveals new insights into nucleotide selection by DNA polymerase I. Nucleic Acids Res 2012; 40:7975-84. [PMID: 22669904 PMCID: PMC3439913 DOI: 10.1093/nar/gks523] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The mechanism by which DNA polymerases achieve their extraordinary accuracy has been intensely studied because of the linkage between this process and mutagenesis and carcinogenesis. Here, we have used single-molecule fluorescence microscopy to study the process of nucleotide selection and exonuclease action. Our results show that the binding of Escherichia coli DNA polymerase I (Klenow fragment) to a primer-template is stabilized by the presence of the next correct dNTP, even in the presence of a large excess of the other dNTPs and rNTPs. These results are consistent with a model where nucleotide selection occurs in the open complex prior to the formation of a closed ternary complex. Our assay can also distinguish between primer binding to the polymerase or exonuclease domain and, contrary to ensemble-averaged studies, we find that stable exonuclease binding only occurs with a mismatched primer terminus.
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Abstract
Much more than ever, nucleic acids are recognized as key building blocks in many of life's processes, and the science of studying these molecular wonders at the single-molecule level is thriving. A new method of doing so has been introduced in the mid 1990's. This method is exceedingly simple: a nanoscale pore that spans across an impermeable thin membrane is placed between two chambers that contain an electrolyte, and voltage is applied across the membrane using two electrodes. These conditions lead to a steady stream of ion flow across the pore. Nucleic acid molecules in solution can be driven through the pore, and structural features of the biomolecules are observed as measurable changes in the trans-membrane ion current. In essence, a nanopore is a high-throughput ion microscope and a single-molecule force apparatus. Nanopores are taking center stage as a tool that promises to read a DNA sequence, and this promise has resulted in overwhelming academic, industrial, and national interest. Regardless of the fate of future nanopore applications, in the process of this 16-year-long exploration, many studies have validated the indispensability of nanopores in the toolkit of single-molecule biophysics. This review surveys past and current studies related to nucleic acid biophysics, and will hopefully provoke a discussion of immediate and future prospects for the field.
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Affiliation(s)
- Meni Wanunu
- Department of Physics, Northeastern University, Boston, MA, United States.
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19
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Dahl JM, Mai AH, Cherf GM, Jetha NN, Garalde DR, Marziali A, Akeson M, Wang H, Lieberman KR. Direct observation of translocation in individual DNA polymerase complexes. J Biol Chem 2012; 287:13407-21. [PMID: 22378784 DOI: 10.1074/jbc.m111.338418] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Complexes of phi29 DNA polymerase and DNA fluctuate on the millisecond time scale between two ionic current amplitude states when captured atop the α-hemolysin nanopore in an applied field. The lower amplitude state is stabilized by complementary dNTP and thus corresponds to complexes in the post-translocation state. We have demonstrated that in the upper amplitude state, the DNA is displaced by a distance of one nucleotide from the post-translocation state. We propose that the upper amplitude state corresponds to complexes in the pre-translocation state. Force exerted on the template strand biases the complexes toward the pre-translocation state. Based on the results of voltage and dNTP titrations, we concluded through mathematical modeling that complementary dNTP binds only to the post-translocation state, and we estimated the binding affinity. The equilibrium between the two states is influenced by active site-proximal DNA sequences. Consistent with the assignment of the upper amplitude state as the pre-translocation state, a DNA substrate that favors the pre-translocation state in complexes on the nanopore is a superior substrate in bulk phase for pyrophosphorolysis. There is also a correlation between DNA sequences that bias complexes toward the pre-translocation state and the rate of exonucleolysis in bulk phase, suggesting that during DNA synthesis the pathway for transfer of the primer strand from the polymerase to exonuclease active site initiates in the pre-translocation state.
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Affiliation(s)
- Joseph M Dahl
- Department of Biomolecular Engineering, Baskin School of Engineering, University of California, Santa Cruz, California 95064, USA
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