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Shan Z, Rivero-Gamez A, Lyumkis D, Horton NC. Two-metal ion mechanism of DNA cleavage by activated, filamentous SgrAI. J Biol Chem 2024; 300:107576. [PMID: 39009341 DOI: 10.1016/j.jbc.2024.107576] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2024] [Revised: 06/21/2024] [Accepted: 07/09/2024] [Indexed: 07/17/2024] Open
Abstract
Enzymes that form filamentous assemblies with modulated enzymatic activities have gained increasing attention in recent years. SgrAI is a sequence specific type II restriction endonuclease that forms polymeric filaments with accelerated DNA cleavage activity and expanded DNA sequence specificity. Prior studies have suggested a mechanistic model linking the structural changes accompanying SgrAI filamentation to its accelerated DNA cleavage activity. In this model, the conformational changes that are specific to filamentous SgrAI maximize contacts between different copies of the enzyme within the filament and create a second divalent cation binding site in each subunit, which in turn facilitates the DNA cleavage reaction. However, our understanding of the atomic mechanism of catalysis is incomplete. Herein, we present two new structures of filamentous SgrAI solved using cryo-EM. The first structure, resolved to 3.3 Å, is of filamentous SgrAI containing an active site mutation that is designed to stall the DNA cleavage reaction, which reveals the enzymatic configuration prior to DNA cleavage. The second structure, resolved to 3.1 Å, is of WT filamentous SgrAI containing cleaved substrate DNA, which reveals the enzymatic configuration at the end of the enzymatic cleavage reaction. Both structures contain the phosphate moiety at the cleavage site and the biologically relevant divalent cation cofactor Mg2+ and define how the Mg2+ cation reconfigures during enzymatic catalysis. The data support a model for the activation mechanism that involves binding of a second Mg2+ in the SgrAI active site as a direct result of filamentation induced conformational changes.
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Affiliation(s)
- Zelin Shan
- The Salk Institute of Biological Sciences, La Jolla, California, USA
| | - Andres Rivero-Gamez
- The Salk Institute of Biological Sciences, La Jolla, California, USA; Department of Molecular Biology, School of Biological Sciences, University of California, San Diego La Jolla, California, USA
| | - Dmitry Lyumkis
- The Salk Institute of Biological Sciences, La Jolla, California, USA; Department of Molecular Biology, School of Biological Sciences, University of California, San Diego La Jolla, California, USA.
| | - Nancy C Horton
- Department of Molecular and Cellular Biology, University of Arizona, Tucson, Arizona, USA.
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2
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Oh DE, Kim HB, Kim TH. Electrochemical DNA Cleavage Sensing for EcoRV Activity and Inhibition with an ERGO Electrode. BIOSENSORS 2024; 14:73. [PMID: 38391992 PMCID: PMC10886839 DOI: 10.3390/bios14020073] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/18/2023] [Revised: 01/27/2024] [Accepted: 01/29/2024] [Indexed: 02/24/2024]
Abstract
An electrochemically reduced graphene oxide (ERGO) electrode-based electrochemical assay was developed for rapid, sensitive, and straightforward analysis of both activity and inhibition of the endonuclease EcoRV. The procedure uses a DNA substrate designed for EcoRV, featuring a double-stranded DNA (dsDNA) region labeled with methylene blue (MB) and a single-stranded DNA (ssDNA) region immobilized on the ERGO surface. The ERGO electrode, immobilized with the DNA substrate, was subsequently exposed to a sample containing EcoRV. Upon enzymatic hydrolysis, the cleaved dsDNA fragments were detached from the ERGO surface, leading to a decrease in the MB concentration near the electrode. This diminished the electron transfer efficiency for MB reduction, resulting in a decreased reduction current. This assay demonstrates excellent specificity and high sensitivity, with a limit of detection (LOD) of 9.5 × 10-3 U mL-1. Importantly, it can also measure EcoRV activity in the presence of aurintricarboxylic acid, a known inhibitor, highlighting its potential for drug discovery and clinical diagnostic applications.
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Affiliation(s)
| | | | - Tae Hyun Kim
- Department of Chemistry, Soonchunhyang University, Asan 31538, Republic of Korea; (D.E.O.); (H.B.K.)
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3
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Shan Z, Ghadirian N, Lyumkis D, Horton NC. Pre-Transition State and Apo Structures of the Filament-Forming Enzyme SgrAI Elucidate Mechanisms of Activation and Substrate Specificity. J Biol Chem 2022; 298:101760. [PMID: 35202658 PMCID: PMC8960973 DOI: 10.1016/j.jbc.2022.101760] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2021] [Revised: 02/14/2022] [Accepted: 02/16/2022] [Indexed: 12/01/2022] Open
Abstract
Enzyme filamentation is a widespread phenomenon that mediates enzyme regulation and function. For the filament-forming sequence-specific DNA endonuclease SgrAI, the process of filamentation both accelerates its DNA cleavage activity and expands its DNA sequence specificity, thus allowing for many additional DNA sequences to be rapidly cleaved. Both outcomes—the acceleration of DNA cleavage and the expansion of sequence specificity—are proposed to regulate critical processes in bacterial innate immunity. However, the mechanistic bases underlying these events remain unclear. Herein, we describe two new structures of the SgrAI enzyme that shed light on its catalytic function. First, we present the cryo-EM structure of filamentous SgrAI bound to intact primary site DNA and Ca2+ resolved to ∼2.5 Å within the catalytic center, which represents the trapped enzyme–DNA complex prior to the DNA cleavage reaction. This structure reveals important conformational changes that contribute to the catalytic mechanism and the binding of a second divalent cation in the enzyme active site, which is expected to contribute to increased DNA cleavage activity of SgrAI in the filamentous state. Second, we present an X-ray crystal structure of DNA-free (apo) SgrAI resolved to 2.0 Å resolution, which reveals a disordered loop involved in DNA recognition. Collectively, these multiple new observations clarify the mechanism of expansion of DNA sequence specificity of SgrAI, including the indirect readout of sequence-dependent DNA structure, changes in protein–DNA interactions, and the disorder-to-order transition of a crucial DNA recognition element.
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Affiliation(s)
- Zelin Shan
- Laboratory of Genetics, The Salk Institute of Biological Sciences, La Jolla, CA, USA 92037
| | - Niloofar Ghadirian
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ, USA 85721
| | - Dmitry Lyumkis
- Laboratory of Genetics, The Salk Institute of Biological Sciences, La Jolla, CA, USA 92037; Department of Integrative Structural and Computational Biology, The Scripps Research Institute, La Jolla, CA, USA 92037.
| | - N C Horton
- Department of Molecular and Cellular Biology, University of Arizona, Tucson, AZ, USA 85721.
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4
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Mandal SC, Maganti L, Mondal M, Chakrabarti J. Microscopic insight to specificity of metal ion cofactor in DNA cleavage by restriction endonuclease EcoRV. Biopolymers 2020; 111:e23396. [PMID: 32858776 DOI: 10.1002/bip.23396] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2020] [Revised: 07/22/2020] [Accepted: 07/27/2020] [Indexed: 11/06/2022]
Abstract
Restriction endonucleases protect bacterial cells against bacteriophage infection by cleaving the incoming foreign DNA into fragments. In presence of Mg2+ ions, EcoRV is able to cleave the DNA but not in presence of Ca2+ , although the protein binds to DNA in presence of both metal ions. We make an attempt to understand this difference using conformational thermodynamics. We calculate the changes in conformational free energy and entropy of conformational degrees of freedom, like DNA base pair steps and dihedral angles of protein residues in Mg2+ (A)-EcoRV-DNA complex compared to Ca2+ (S)-EcoRV-DNA complex using all-atom molecular dynamics (MD) trajectories of the complexes. We find that despite conformational stability and order in both complexes, the individual degrees of freedom behave differently in the presence of two different metal ions. The base pairs in cleavage region are highly disordered in Ca2+ (S)-EcoRV-DNA compared to Mg2+ (A)-EcoRV-DNA. One of the acidic residues ASP90, coordinating to the metal ion in the vicinity of the cleavage site, is conformationally destabilized and disordered, while basic residue LYS92 gets conformational stability and order in Ca2+ (S) bound complex than in Mg2+ (A) bound complex. The enhanced fluctuations hinder placement of the metal ion in the vicinity of the scissile phosphate of DNA. Similar loss of conformational stability and order in the cleavage region is observed by the replacement of the metal ion. Considering the placement of the metal ion near scissile phosphate as requirement for cleavage action, our results suggest that the changes in conformational stability and order of the base pair steps and the protein residues lead to cofactor sensitivity of the enzyme. Our method based on fluctuations of microscopic conformational variables can be applied to understand enzyme activities in other protein-DNA systems.
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Affiliation(s)
- Sasthi Charan Mandal
- Department of Chemical, Biological and Macro-Molecular Sciences, S.N. Bose National Centre for Basic Sciences, Kolkata, India
| | - Lakshmi Maganti
- Computational Science Division, Saha Institute of Nuclear Physics, Kolkata, India
| | - Manas Mondal
- Shenzhen Bay Laboratory, Institute of Systems and Physical Biology, Shenzhen, China
| | - Jaydeb Chakrabarti
- Department of Chemical, Biological and Macro-Molecular Sciences, S.N. Bose National Centre for Basic Sciences, Kolkata, India.,Thematic Unit of Excellence on Computational Materials Science, and Technical Research Centre, S. N. Bose National Centre for Basic Sciences, Kolkata, India
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5
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Prisecaru A, Devereux M, Barron N, McCann M, Colleran J, Casey A, McKee V, Kellett A. Potent oxidative DNA cleavage by the di-copper cytotoxin: [Cu2(μ-terephthalate)(1,10-phen)4]2+. Chem Commun (Camb) 2012; 48:6906-8. [DOI: 10.1039/c2cc31023f] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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6
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Zahran M, Berezniak T, Imhof P, Smith JC. Role of magnesium ions in DNA recognition by the EcoRV restriction endonuclease. FEBS Lett 2011; 585:2739-43. [DOI: 10.1016/j.febslet.2011.07.036] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2011] [Revised: 07/20/2011] [Accepted: 07/25/2011] [Indexed: 10/17/2022]
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Uyar A, Kurkcuoglu O, Nilsson L, Doruker P. The elastic network model reveals a consistent picture on intrinsic functional dynamics of type II restriction endonucleases. Phys Biol 2011; 8:056001. [PMID: 21791727 DOI: 10.1088/1478-3975/8/5/056001] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The vibrational dynamics of various type II restriction endonucleases, in complex with cognate/non-cognate DNA and in the apo form, are investigated with the elastic network model in order to reveal common functional mechanisms in this enzyme family. Scissor-like and tong-like motions observed in the slowest modes of all enzymes and their complexes point to common DNA recognition and cleavage mechanisms. Normal mode analysis further points out that the scissor-like motion has an important role in differentiating between cognate and non-cognate sequences at the recognition site, thus implying its catalytic relevance. Flexible regions observed around the DNA-binding site of the enzyme usually concentrate on the highly conserved β-strands, especially after DNA binding. These β-strands may have a structurally stabilizing role in functional dynamics for target site recognition and cleavage. In addition, hot spot residues based on high-frequency modes reveal possible communication pathways between the two distant cleavage sites in the enzyme family. Some of these hot spots also exist on the shortest path between the catalytic sites and are highly conserved.
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Affiliation(s)
- A Uyar
- Department of Chemical Engineering and Polymer Research Center, Bogazici University, 34342 Bebek, Istanbul, Turkey
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8
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Smith RM, Josephsen J, Szczelkun MD. An Mrr-family nuclease motif in the single polypeptide restriction-modification enzyme LlaGI. Nucleic Acids Res 2010; 37:7231-8. [PMID: 19793866 PMCID: PMC2790908 DOI: 10.1093/nar/gkp795] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Bioinformatic analysis of the putative nuclease domain of the single polypeptide restriction–modification enzyme LlaGI reveals amino acid motifs characteristic of the Escherichia coli methylated DNA-specific Mrr endonuclease. Using mutagenesis, we examined the role of the conserved residues in both DNA translocation and cleavage. Mutations in those residues predicted to play a role in DNA hydrolysis produced enzymes that could translocate on DNA but were either unable to cleave the polynucleotide track or had reduced nuclease activity. Cleavage by LlaGI is not targeted to methylated DNA, suggesting that the conserved motifs in the Mrr domain are a conventional sub-family of the PD-(D/E)XK superfamily of DNA nucleases.
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Affiliation(s)
- Rachel M Smith
- DNA-Protein Interactions Unit, Department of Biochemistry, School of Medical Sciences, University of Bristol, Bristol, BS8 1TD, UK
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9
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Imhof P, Fischer S, Smith JC. Catalytic Mechanism of DNA Backbone Cleavage by the Restriction Enzyme EcoRV: A Quantum Mechanical/Molecular Mechanical Analysis. Biochemistry 2009; 48:9061-75. [DOI: 10.1021/bi900585m] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Petra Imhof
- Computational Molecular Biophysics, IWR, University of Heidelberg, Im Neuenheimer Feld 368, 69120 Heidelberg, Germany
| | - Stefan Fischer
- Computational Biochemistry, IWR, University of Heidelberg, Im Neuenheimer Feld 368, 69120 Heidelberg, Germany
| | - Jeremy C. Smith
- Computational Molecular Biophysics, IWR, University of Heidelberg, Im Neuenheimer Feld 368, 69120 Heidelberg, Germany
- Oak Ridge National Laboratory, P.O. Box 2008 MS 6309, Oak Ridge, Tennessee 37831-6309
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10
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Babic AC, Little EJ, Manohar VM, Bitinaite J, Horton NC. DNA distortion and specificity in a sequence-specific endonuclease. J Mol Biol 2008; 383:186-204. [PMID: 18762194 PMCID: PMC2605692 DOI: 10.1016/j.jmb.2008.08.032] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2008] [Revised: 08/04/2008] [Accepted: 08/12/2008] [Indexed: 11/30/2022]
Abstract
Five new structures of the Q138F HincII enzyme bound to a total of three different DNA sequences and three different metal ions (Ca(2+), Mg(2+), and Mn(2+)) are presented. While previous structures were produced from soaking Ca(2+) into preformed Q138F HincII/DNA crystals, the new structures are derived from cocrystallization with Ca(2+), Mg(2+), or Mn(2+). The Mn(2)(+)-bound structure provides the first view of a product complex of Q138F HincII with cleaved DNA. Binding studies and a crystal structure show how Ca(2+) allows trapping of a Q138F HincII complex with noncognate DNA in a catalytically incompetent conformation. Many Q138F HincII/DNA structures show asymmetry, despite the binding of a symmetric substrate by a symmetric enzyme. The various complexes are fit into a model describing the different conformations of the DNA-bound enzyme and show how DNA conformational energetics determine DNA-cleavage rates by the Q138F HincII enzyme.
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Affiliation(s)
- Andrea C. Babic
- Department of Biochemistry and Molecular Biophysics, University of Arizona, Tucson, AZ, 85721
| | - Elizabeth J. Little
- Department of Biochemistry and Molecular Biophysics, University of Arizona, Tucson, AZ, 85721
| | - Veena M. Manohar
- Department of Biochemistry and Molecular Biophysics, University of Arizona, Tucson, AZ, 85721
| | | | - Nancy C. Horton
- Department of Biochemistry and Molecular Biophysics, University of Arizona, Tucson, AZ, 85721
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11
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Niu Y, Tenney K, Li H, Gimble FS. Engineering variants of the I-SceI homing endonuclease with strand-specific and site-specific DNA-nicking activity. J Mol Biol 2008; 382:188-202. [PMID: 18644379 PMCID: PMC2700736 DOI: 10.1016/j.jmb.2008.07.010] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2008] [Revised: 07/03/2008] [Accepted: 07/04/2008] [Indexed: 10/21/2022]
Abstract
The number of strand-specific nicking endonucleases that are currently available for laboratory procedures and applications in vivo is limited, and none is sufficiently specific to nick single target sites within complex genomes. The extreme target specificity of homing endonucleases makes them attractive candidates for engineering high-specificity nicking endonucleases. I-SceI is a monomeric homing enzyme that recognizes an 18 bp asymmetric target sequence, and cleaves both DNA strands to leave 3'-overhangs of 4 bp. In single turnover experiments using plasmid substrates, I-SceI generates transient open circle intermediates during the conversion of supercoiled to linear DNA, indicating that the enzyme cleaves the two DNA strands sequentially. A novel hairpin substrate was used to demonstrate that although wild-type I-SceI cleaves either the top or bottom DNA strand first to generate two nicked DNA intermediates, the enzyme has a preference for cleaving the bottom strand. The kinetics data are consistent with a parallel sequential reaction mechanism. Substitution of two pseudo-symmetric residues, Lys122 and Lys223, markedly reduces top and bottom-strand cleavage, respectively, to generate enzymes with significant strand- and sequence-specific nicking activity. The two active sites are partially interdependent, since alterations to one site affect the second. The kinetics analysis is consistent with X-ray crystal structures of I-SceI/DNA complexes that reveal a role for the lysines in establishing important solvent networks that include nucleophilic water molecules thought to attack the scissile phosphodiester bonds.
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Affiliation(s)
- Yan Niu
- Department of Biochemistry, Purdue University, West Lafayette, IN 47907, USA
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12
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Warshel A, Sharma PK, Kato M, Xiang Y, Liu H, Olsson MHM. Electrostatic basis for enzyme catalysis. Chem Rev 2007; 106:3210-35. [PMID: 16895325 DOI: 10.1021/cr0503106] [Citation(s) in RCA: 966] [Impact Index Per Article: 56.8] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Arieh Warshel
- Department of Chemistry, University of Southern California, SGM Building 418, 3620 McClintock Avenue, Los Angeles, California 90089-1062, USA.
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13
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Hiller DA, Perona JJ. Positively charged C-terminal subdomains of EcoRV endonuclease: contributions to DNA binding, bending, and cleavage. Biochemistry 2006; 45:11453-63. [PMID: 16981705 PMCID: PMC2515858 DOI: 10.1021/bi0606400] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The carboxy-terminal subdomains of the homodimeric EcoRV restriction endonuclease each bear a net charge of +4 and are positioned on the inner concave surface of the 50 degree DNA bend that is induced by the enzyme. A complete kinetic and structural analysis of a truncated EcoRV mutant lacking these domains was performed to assess the importance of this diffuse charge in facilitating DNA binding, bending, and cleavage. At the level of formation of an enzyme-DNA complex, the association rate for the dimeric mutant enzyme was sharply decreased by 10(3)-fold, while the equilibrium dissociation constant was weakened by nearly 10(6)-fold compared with that of wild-type EcoRV. Thus, the C-terminal subdomains strongly stabilize the enzyme-DNA ground-state complex in which the DNA is known to be bent. Further, the extent of DNA bending as observed by fluorescence resonance energy transfer was also significantly decreased. The crystal structure of the truncated enzyme bound to DNA and calcium ions at 2.4 A resolution reveals that the global fold is preserved and suggests that a divalent metal ion crucial to catalysis is destabilized in the active site. This may explain the 100-fold decrease in the rate of metal-dependent phosphoryl transfer observed for the mutant. These results show that diffuse positive charge associated with the C-terminal subdomains of EcoRV plays a key role in DNA association, bending, and cleavage.
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Affiliation(s)
| | - John J. Perona
- Corresponding author Telephone: 805−893−7389 FAX: 805−893−4120
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Hiller DA, Rodriguez AM, Perona JJ. Non-cognate Enzyme–DNA Complex: Structural and Kinetic Analysis of EcoRV Endonuclease Bound to the EcoRI Recognition Site GAATTC. J Mol Biol 2005; 354:121-36. [PMID: 16236314 DOI: 10.1016/j.jmb.2005.09.046] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2005] [Revised: 09/14/2005] [Accepted: 09/15/2005] [Indexed: 11/25/2022]
Abstract
The crystal structure of EcoRV endonuclease bound to non-cognate DNA at 2.0 angstroms resolution shows that very small structural adaptations are sufficient to ensure the extreme sequence specificity characteristic of restriction enzymes. EcoRV bends its specific GATATC site sharply by 50 degrees into the major groove at the center TA step, generating unusual base-base interactions along each individual DNA strand. In the symmetric non-cognate complex bound to GAATTC, the center step bend is relaxed to avoid steric hindrance caused by the different placement of the exocyclic thymine methyl groups. The decreased base-pair unstacking in turn leads to small conformational rearrangements in the sugar-phosphate backbone, sufficient to destabilize binding of crucial divalent metal ions in the active site. A second crystal structure of EcoRV bound to the base-analog GAAUTC site shows that the 50 degrees center-step bend of the DNA is restored. However, while divalent metals bind at high occupancy in this structure, one metal ion shifts away from binding at the scissile DNA phosphate to a position near the 3'-adjacent phosphate group. This may explain why the 10(4)-fold attenuated cleavage efficiency toward GAATTC is reconstituted by less than tenfold toward GAAUTC. Examination of DNA binding and bending by equilibrium and stopped-flow florescence quenching and fluorescence resonance energy transfer (FRET) methods demonstrates that the capacity of EcoRV to bend the GAATTC non-cognate site is severely limited, but that full bending of GAAUTC is achieved at only a threefold reduced rate compared with the cognate complex. Together, the structural and biochemical data demonstrate the existence of distinct mechanisms for ensuring specificity at the bending and catalytic steps, respectively. The limited conformational rearrangements observed in the EcoRV non-cognate complex provide a sharp contrast to the extensive structural changes found in a non-cognate BamHI-DNA crystal structure, thus demonstrating a diversity of mechanisms by which restriction enzymes are able to achieve specificity.
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Affiliation(s)
- David A Hiller
- Department of Chemistry and Biochemistry, and Interdepartmental Program in Biomolecular Science and Engineering, University of California at Santa Barbara, Santa Barbara, CA 93106-9510, USA
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15
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Etzkorn C, Horton NC. Mechanistic insights from the structures of HincII bound to cognate DNA cleaved from addition of Mg2+ and Mn2+. J Mol Biol 2004; 343:833-49. [PMID: 15476804 DOI: 10.1016/j.jmb.2004.08.082] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2004] [Revised: 08/24/2004] [Accepted: 08/27/2004] [Indexed: 11/16/2022]
Abstract
The three-dimensional X-ray crystal structures of HincII bound to cognate DNA containing GTCGAC and Mn(2+) or Mg(2+), at 2.50A and 2.95A resolution, respectively, are presented. In both structures, the DNA is found cleaved, and the positions of the active-site groups, cleaved phosphate group, and 3' oxygen atom of the leaving group are in very similar positions. Two highly occupied Mn(2+) positions are found in each active site of the four crystallographically independent subunit copies in the HincII/DNA/Mn(2+) structure. The manganese ion closest to the previously identified single Ca(2+) position of HincII is shifted 1.7A and has lost direct ligation to the active-site aspartate residue, Asp127. A Mn(2+)-ligated water molecule in a position analogous to that seen in the HincII/DNA/Ca(2+) structure, and proposed to be the attacking nucleophile, is beyond hydrogen bonding distance from the active-site lysine residue, Lys129, but remains within hydrogen bonding distance from the proRp oxygen atom of the phosphate group 3' to the scissile phosphate group. In addition, the position of the cleaved phosphate group is on the opposite side of the axis connecting the two metal ions relative to that found in the BamHI/product DNA/Mn(2+) structure. Mechanistic implications are discussed, and a model for the two-metal-ion mechanism of DNA cleavage by HincII is proposed.
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Affiliation(s)
- Christopher Etzkorn
- Department of Biochemistry and Molecular Biophysics, University of Arizona, Tucson, AZ 85721, USA
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17
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Pingoud V, Conzelmann C, Kinzebach S, Sudina A, Metelev V, Kubareva E, Bujnicki JM, Lurz R, Lüder G, Xu SY, Pingoud A. PspGI, a type II restriction endonuclease from the extreme thermophile Pyrococcus sp.: structural and functional studies to investigate an evolutionary relationship with several mesophilic restriction enzymes. J Mol Biol 2003; 329:913-29. [PMID: 12798682 DOI: 10.1016/s0022-2836(03)00523-0] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
We present here the first detailed biochemical analysis of an archaeal restriction enzyme. PspGI shows sequence similarity to SsoII, EcoRII, NgoMIV and Cfr10I, which recognize related DNA sequences. We demonstrate here that PspGI, like SsoII and unlike EcoRII or NgoMIV and Cfr10I, interacts with and cleaves DNA as a homodimer and is not stimulated by simultaneous binding to two recognition sites. PspGI and SsoII differ in their basic biochemical properties, viz. stability against chemical denaturation and proteolytic digestion, DNA binding and the pH, MgCl(2) and salt-dependence of their DNA cleavage activity. In contrast, the results of mutational analyses and cross-link experiments show that PspGI and SsoII have a very similar DNA binding site and catalytic center as NgoMIV and Cfr10I (whose crystal structures are known), and presumably also as EcoRII, in spite of the fact that these enzymes, which all recognize variants of the sequence -/CC-GG- (/ denotes the site of cleavage), are representatives of different subgroups of type II restriction endonucleases. A sequence comparison of all known restriction endonuclease sequences, furthermore, suggests that several enzymes recognizing other DNA sequences also share amino acid sequence similarities with PspGI, SsoII and EcoRII in the region of the presumptive active site. These results are discussed in an evolutionary context.
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Affiliation(s)
- Vera Pingoud
- Institut für Biochemie, Justus-Liebig-Universität, Heinrich-Buff-Ring 58, D-35392 Giessen, Germany.
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18
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Biochemical Genetics. Biochemistry 2001. [DOI: 10.1016/b978-012492543-4/50029-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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