1
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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 2024:107576. [PMID: 39009341 DOI: 10.1016/j.jbc.2024.107576] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [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-electron microscopy (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, CA, USA 92037
| | - Andres Rivero-Gamez
- The Salk Institute of Biological Sciences, La Jolla, CA, USA 92037; Department of Molecular Biology, School of Biological Sciences, University of California, San Diego, La Jolla, CA, USA 92093
| | - Dmitry Lyumkis
- The Salk Institute of Biological Sciences, La Jolla, CA, USA 92037; Department of Molecular Biology, School of Biological Sciences, University of California, San Diego, La Jolla, CA, USA 92093.
| | - Nancy C Horton
- Department of Molecular and Cellular Biology, University of Arizona, Tucson, AZ, USA 85721.
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2
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Ghadirian N, Morgan RD, Horton NC. DNA Sequence Control of Enzyme Filamentation and Activation of the SgrAI Endonuclease. Biochemistry 2024; 63:326-338. [PMID: 38207281 DOI: 10.1021/acs.biochem.3c00313] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2024]
Abstract
Enzyme polymerization (also known as filamentation) has emerged as a new layer of enzyme regulation. SgrAI is a sequence-dependent DNA endonuclease that forms polymeric filaments with enhanced DNA cleavage activity as well as altered DNA sequence specificity. To better understand this unusual regulatory mechanism, full global kinetic modeling of the reaction pathway, including the enzyme filamentation steps, has been undertaken. Prior work with the primary DNA recognition sequence cleaved by SgrAI has shown how the kinetic rate constants of each reaction step are tuned to maximize activation and DNA cleavage while minimizing the extent of DNA cleavage to the host genome. In the current work, we expand on our prior study by now including DNA cleavage of a secondary recognition sequence, to understand how the sequence of the bound DNA modulates filamentation and activation of SgrAI. The work shows that an allosteric equilibrium between low and high activity states is modulated by the sequence of bound DNA, with primary sequences more prone to activation and filament formation, while SgrAI bound to secondary recognition sequences favor the low (and nonfilamenting) state by up to 40-fold. In addition, the degree of methylation of secondary sequences in the host organism, Streptomyces griseus, is now reported for the first time and shows that as predicted, these sequences are left unprotected from the SgrAI endonuclease making sequence specificity critical in this unusual filament-forming enzyme.
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Affiliation(s)
- Niloofar Ghadirian
- Department of Chemistry & Biochemistry, University of Arizona, Tucson, Arizona 85721, United States
| | - Richard D Morgan
- New England Biolabs, Inc., Ipswich, Massachusetts 01938, United States
| | - Nancy C Horton
- Department of Molecular and Cellular Biology, University of Arizona, Tucson, Arizona 85721, United States
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3
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The role of filamentation in activation and DNA sequence specificity of the sequence-specific endonuclease SgrAI. Biochem Soc Trans 2022; 50:1703-1714. [PMID: 36398769 PMCID: PMC9788392 DOI: 10.1042/bst20220547] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2022] [Revised: 10/09/2022] [Accepted: 10/12/2022] [Indexed: 11/19/2022]
Abstract
Filament formation by metabolic, biosynthetic, and other enzymes has recently come into focus as a mechanism to fine-tune enzyme activity in the cell. Filamentation is key to the function of SgrAI, a sequence-specific DNA endonuclease that has served as a model system to provide some of the deepest insights into the biophysical characteristics of filamentation and its functional consequences. Structure-function analyses reveal that, in the filamentous state, SgrAI stabilizes an activated enzyme conformation that leads to accelerated DNA cleavage activity and expanded DNA sequence specificity. The latter is thought to be mediated by sequence-specific DNA structure, protein-DNA interactions, and a disorder-to-order transition in the protein, which collectively affect the relative stabilities of the inactive, non-filamentous conformation and the active, filamentous conformation of SgrAI bound to DNA. Full global kinetic modeling of the DNA cleavage pathway reveals a slow, rate-limiting, second-order association rate constant for filament assembly, and simulations of in vivo activity predict that filamentation is superior to non-filamenting mechanisms in ensuring rapid activation and sequestration of SgrAI's DNA cleavage activity on phage DNA and away from the host chromosome. In vivo studies demonstrate the critical requirement for accelerated DNA cleavage by SgrAI in its biological role to safeguard the bacterial host. Collectively, these data have advanced our understanding of how filamentation can regulate enzyme structure and function, while the experimental strategies used for SgrAI can be applied to other enzymatic systems to identify novel functional roles for filamentation.
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4
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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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5
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Manakova E, Mikutenaite M, Golovenko D, Gražulis S, Tamulaitiene G. Crystal structure of restriction endonuclease Kpn2I of CCGG-family. Biochim Biophys Acta Gen Subj 2021; 1865:129926. [PMID: 33965438 DOI: 10.1016/j.bbagen.2021.129926] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2020] [Revised: 05/02/2021] [Accepted: 05/04/2021] [Indexed: 10/21/2022]
Abstract
BACKGROUND Restriction endonucleases belong to prokaryotic restriction-modification systems, that protect host cells from invading DNA. Type II restriction endonucleases recognize short 4-8 bp sequences in the target DNA and cut both DNA strands producing double strand breaks. Type II restriction endonuclease Kpn2I cleaves 5'-T/CCGGA DNA sequence ("/" marks the cleavage position). Analysis of protein sequences suggested that Kpn2I belongs to the CCGG-family, which contains ten enzymes that recognize diverse nucleotides outside the conserved 5'-CCGG core and share similar motifs for the 5'-CCGG recognition and cleavage. METHODS We solved a crystal structure of Kpn2I in a DNA-free form at 2.88 Å resolution. From the crystal structure we predicted active center and DNA recognition residues and tested them by mutational analysis. We estimated oligomeric state of Kpn2I by SEC-MALS and performed plasmid DNA cleavage assay to elucidate DNA cleavage mechanism. RESULTS Structure comparison confirmed that Kpn2I shares a conserved active site and structural determinants for the 5'-CCGG tetranucleotide recognition with other restriction endonucleases of the CCGG-family. Guided by structural similarity between Kpn2I and the CCGG-family restriction endonucleases PfoI and AgeI, Kpn2I residues involved in the outer base pair recognition were proposed. CONCLUSIONS Kpn2I is an orthodox Type IIP restriction endonuclease, which acts as a dimer. Kpn2I shares structural similarity to the CCGG-family restriction endonucleases PfoI, AgeI and PspGI. GENERAL SIGNIFICANCE The Kpn2I structure concluded the studies of the CCGG-family, covering detailed structural and biochemical characterization of eleven restriction enzymes and their complexes with DNA.
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Affiliation(s)
- Elena Manakova
- Institute of Biotechnology, Life Sciences Center, Vilnius University, Sauletekio al. 7, LT-10257 Vilnius, Lithuania
| | - Migle Mikutenaite
- Institute of Biotechnology, Life Sciences Center, Vilnius University, Sauletekio al. 7, LT-10257 Vilnius, Lithuania
| | - Dmitrij Golovenko
- Institute of Biotechnology, Life Sciences Center, Vilnius University, Sauletekio al. 7, LT-10257 Vilnius, Lithuania
| | - Saulius Gražulis
- Institute of Biotechnology, Life Sciences Center, Vilnius University, Sauletekio al. 7, LT-10257 Vilnius, Lithuania
| | - Giedre Tamulaitiene
- Institute of Biotechnology, Life Sciences Center, Vilnius University, Sauletekio al. 7, LT-10257 Vilnius, Lithuania.
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6
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Park CK, Horton NC. Structures, functions, and mechanisms of filament forming enzymes: a renaissance of enzyme filamentation. Biophys Rev 2019; 11:927-994. [PMID: 31734826 PMCID: PMC6874960 DOI: 10.1007/s12551-019-00602-6] [Citation(s) in RCA: 57] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2019] [Accepted: 10/24/2019] [Indexed: 12/19/2022] Open
Abstract
Filament formation by non-cytoskeletal enzymes has been known for decades, yet only relatively recently has its wide-spread role in enzyme regulation and biology come to be appreciated. This comprehensive review summarizes what is known for each enzyme confirmed to form filamentous structures in vitro, and for the many that are known only to form large self-assemblies within cells. For some enzymes, studies describing both the in vitro filamentous structures and cellular self-assembly formation are also known and described. Special attention is paid to the detailed structures of each type of enzyme filament, as well as the roles the structures play in enzyme regulation and in biology. Where it is known or hypothesized, the advantages conferred by enzyme filamentation are reviewed. Finally, the similarities, differences, and comparison to the SgrAI endonuclease system are also highlighted.
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Affiliation(s)
- Chad K. Park
- Department of Molecular and Cellular Biology, University of Arizona, Tucson, AZ 85721 USA
| | - Nancy C. Horton
- Department of Molecular and Cellular Biology, University of Arizona, Tucson, AZ 85721 USA
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7
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Polley S, Lyumkis D, Horton NC. Mechanism of Filamentation-Induced Allosteric Activation of the SgrAI Endonuclease. Structure 2019; 27:1497-1507.e3. [PMID: 31447289 PMCID: PMC6774820 DOI: 10.1016/j.str.2019.08.001] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2019] [Revised: 07/10/2019] [Accepted: 08/02/2019] [Indexed: 02/07/2023]
Abstract
Filament formation by enzymes is increasingly recognized as an important phenomenon with potentially unique regulatory properties and biological roles. SgrAI is an allosterically regulated type II restriction endonuclease that forms filaments with enhanced DNA cleavage activity and altered sequence specificity. Here, we present the cryoelectron microscopy (cryo-EM) structure of the filament of SgrAI in its activated configuration. The structural data illuminate the mechanistic origin of hyperaccelerated DNA cleavage activity and suggests how indirect DNA sequence readout within filamentous SgrAI may enable recognition of substantially more nucleotide sequences than its low-activity form, thereby altering and partially relaxing its DNA sequence specificity. Together, substrate DNA binding, indirect readout, and filamentation simultaneously enhance SgrAI's catalytic activity and modulate substrate preference. This unusual enzyme mechanism may have evolved to perform the specialized functions of bacterial innate immunity in rapid defense against invading phage DNA without causing damage to the host DNA.
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Affiliation(s)
- Smarajit Polley
- Department of Biophysics, Bose Institute, Kolkata 700054, India
| | - Dmitry Lyumkis
- Laboratory of Genetics, Salk Institute for Biological Studies, La Jolla, CA 92037, USA.
| | - Nancy C Horton
- Department of Molecular and Cellular Biology, University of Arizona, Tucson, AZ 85721, USA.
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8
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Tamulaitiene G, Manakova E, Jovaisaite V, Tamulaitis G, Grazulis S, Bochtler M, Siksnys V. Unique mechanism of target recognition by PfoI restriction endonuclease of the CCGG-family. Nucleic Acids Res 2019; 47:997-1010. [PMID: 30445642 PMCID: PMC6344858 DOI: 10.1093/nar/gky1137] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2018] [Accepted: 10/26/2018] [Indexed: 01/23/2023] Open
Abstract
Restriction endonucleases (REs) of the CCGG-family recognize a set of 4–8 bp target sequences that share a common CCGG or CCNGG core and possess PD…D/ExK nuclease fold. REs that interact with 5 bp sequence 5′-CCNGG flip the central N nucleotides and ‘compress’ the bound DNA to stack the inner base pairs to mimic the CCGG sequence. PfoI belongs to the CCGG-family and cleaves the 7 bp sequence 5′-T|CCNGGA ("|" designates cleavage position). We present here crystal structures of PfoI in free and DNA-bound forms that show unique active site arrangement and mechanism of sequence recognition. Structures and mutagenesis indicate that PfoI features a permuted E…ExD…K active site that differs from the consensus motif characteristic to other family members. Although PfoI also flips the central N nucleotides of the target sequence it does not ‘compress’ the bound DNA. Instead, PfoI induces a drastic change in DNA backbone conformation that shortens the distance between scissile phosphates to match that in the unperturbed CCGG sequence. Our data demonstrate the diversity and versatility of structural mechanisms employed by restriction enzymes for recognition of related DNA sequences.
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Affiliation(s)
- Giedre Tamulaitiene
- Institute of Biotechnology, Vilnius University, Sauletekio al. 7, LT-10257 Vilnius, Lithuania
| | - Elena Manakova
- Institute of Biotechnology, Vilnius University, Sauletekio al. 7, LT-10257 Vilnius, Lithuania
| | - Virginija Jovaisaite
- Institute of Biotechnology, Vilnius University, Sauletekio al. 7, LT-10257 Vilnius, Lithuania
| | - Gintautas Tamulaitis
- Institute of Biotechnology, Vilnius University, Sauletekio al. 7, LT-10257 Vilnius, Lithuania
| | - Saulius Grazulis
- Institute of Biotechnology, Vilnius University, Sauletekio al. 7, LT-10257 Vilnius, Lithuania
| | - Matthias Bochtler
- Laboratory of Structural Biology, International Institute of Molecular and Cell Biology, Trojdena 4, 02-109 Warsaw, Poland.,Dept. of Bioinformatics, Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Pawinskiego 5a, 02-106 Warsaw, Poland
| | - Virginijus Siksnys
- Institute of Biotechnology, Vilnius University, Sauletekio al. 7, LT-10257 Vilnius, Lithuania
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9
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Park CK, Sanchez JL, Barahona C, Basantes LE, Sanchez J, Hernandez C, Horton NC. The run-on oligomer filament enzyme mechanism of SgrAI: Part 1. Assembly kinetics of the run-on oligomer filament. J Biol Chem 2018; 293:14585-14598. [PMID: 30068553 DOI: 10.1074/jbc.ra118.003680] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2018] [Revised: 07/30/2018] [Indexed: 01/06/2023] Open
Abstract
Filament or run-on oligomer formation by metabolic enzymes is now recognized as a widespread phenomenon having potentially unique enzyme regulatory properties and biological roles, and its dysfunction is implicated in human diseases such as cancer, diabetes, and developmental disorders. SgrAI is a bacterial allosteric type II restriction endonuclease that binds to invading phage DNA, may protect the host DNA from off-target cleavage activity, and forms run-on oligomeric filaments with enhanced DNA-cleavage activity and altered DNA sequence specificity. However, the mechanisms of SgrAI filament growth, cooperativity in filament formation, sequestration of enzyme activity, and advantages over other filament mechanisms remain unknown. In this first of a two-part series, we developed methods and models to derive association and dissociation rate constants of DNA-bound SgrAI in run-on oligomers and addressed the specific questions of cooperativity and filament growth mechanisms. We show that the derived rate constants are consistent with the run-on oligomer sizes determined by EM analysis and are most consistent with a noncooperative growth mode of the run-on oligomer. These models and methods are extended in the accompanying article to include the full DNA-cleavage pathway and address specific questions related to the run-on oligomer mechanism including the sequestration of DNA-cleavage activity and trapping of products.
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Affiliation(s)
- Chad K Park
- From the Department of Molecular and Cellular Biology, University of Arizona, Tucson, Arizona 85721
| | - Jonathan L Sanchez
- From the Department of Molecular and Cellular Biology, University of Arizona, Tucson, Arizona 85721
| | - Claudia Barahona
- From the Department of Molecular and Cellular Biology, University of Arizona, Tucson, Arizona 85721
| | - L Emilia Basantes
- From the Department of Molecular and Cellular Biology, University of Arizona, Tucson, Arizona 85721
| | - Juan Sanchez
- From the Department of Molecular and Cellular Biology, University of Arizona, Tucson, Arizona 85721
| | - Christian Hernandez
- From the Department of Molecular and Cellular Biology, University of Arizona, Tucson, Arizona 85721
| | - N C Horton
- From the Department of Molecular and Cellular Biology, University of Arizona, Tucson, Arizona 85721
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10
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Park CK, Sanchez JL, Barahona C, Basantes LE, Sanchez J, Hernandez C, Horton NC. The run-on oligomer filament enzyme mechanism of SgrAI: Part 2. Kinetic modeling of the full DNA cleavage pathway. J Biol Chem 2018; 293:14599-14615. [PMID: 30054273 DOI: 10.1074/jbc.ra118.003682] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2018] [Revised: 07/17/2018] [Indexed: 11/06/2022] Open
Abstract
Filament or run-on oligomer formation by enzymes is now recognized as a widespread phenomenon with potentially unique enzyme regulatory properties and biological roles. SgrAI is an allosteric type II restriction endonuclease that forms run-on oligomeric filaments with activated DNA cleavage activity and altered DNA sequence specificity. In this two-part work, we measure individual steps in the run-on oligomer filament mechanism to address specific questions of cooperativity, trapping, filament growth mechanisms, and sequestration of activity using fluorophore-labeled DNA, kinetic FRET measurements, and reaction modeling with global data fitting. The final models and rate constants show that the assembly step involving association of SgrAI-DNA complexes into the run-on oligomer filament is relatively slow (3-4 orders of magnitude slower than diffusion limited) and rate-limiting at low to moderate concentrations of SgrAI-DNA. The disassembly step involving dissociation of complexes of SgrAI-DNA from each other in the run-on oligomer filament is the next slowest step but is fast enough to limit the residence time of any one copy of SgrAI or DNA within the dynamic filament. Further, the rate constant for DNA cleavage is found to be 4 orders of magnitude faster in the run-on oligomer filament than in isolated SgrAI-DNA complexes and faster than dissociation of SgrAI-DNA complexes from the run-on oligomer filament, making the reaction efficient in that each association into the filament likely leads to DNA cleavage before filament dissociation.
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Affiliation(s)
- Chad K Park
- From the Department of Molecular and Cellular Biology, University of Arizona, Tucson, Arizona 85721
| | - Jonathan L Sanchez
- From the Department of Molecular and Cellular Biology, University of Arizona, Tucson, Arizona 85721
| | - Claudia Barahona
- From the Department of Molecular and Cellular Biology, University of Arizona, Tucson, Arizona 85721
| | - L Emilia Basantes
- From the Department of Molecular and Cellular Biology, University of Arizona, Tucson, Arizona 85721
| | - Juan Sanchez
- From the Department of Molecular and Cellular Biology, University of Arizona, Tucson, Arizona 85721
| | - Christian Hernandez
- From the Department of Molecular and Cellular Biology, University of Arizona, Tucson, Arizona 85721
| | - N C Horton
- From the Department of Molecular and Cellular Biology, University of Arizona, Tucson, Arizona 85721
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11
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Shah S, Sanchez J, Stewart A, Piperakis MM, Cosstick R, Nichols C, Park CK, Ma X, Wysocki V, Bitinaite J, Horton NC. Probing the run-on oligomer of activated SgrAI bound to DNA. PLoS One 2015; 10:e0124783. [PMID: 25880668 PMCID: PMC4399878 DOI: 10.1371/journal.pone.0124783] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2015] [Accepted: 03/05/2015] [Indexed: 02/04/2023] Open
Abstract
SgrAI is a type II restriction endonuclease with an unusual mechanism of activation involving run-on oligomerization. The run-on oligomer is formed from complexes of SgrAI bound to DNA containing its 8 bp primary recognition sequence (uncleaved or cleaved), and also binds (and thereby activates for DNA cleavage) complexes of SgrAI bound to secondary site DNA sequences which contain a single base substitution in either the 1st/8th or the 2nd/7th position of the primary recognition sequence. This modulation of enzyme activity via run-on oligomerization is a newly appreciated phenomenon that has been shown for a small but increasing number of enzymes. One outstanding question regarding the mechanistic model for SgrAI is whether or not the activating primary site DNA must be cleaved by SgrAI prior to inducing activation. Herein we show that an uncleavable primary site DNA containing a 3'-S-phosphorothiolate is in fact able to induce activation. In addition, we now show that cleavage of secondary site DNA can be activated to nearly the same degree as primary, provided a sufficient number of flanking base pairs are present. We also show differences in activation and cleavage of the two types of secondary site, and that effects of selected single site substitutions in SgrAI, as well as measured collisional cross-sections from previous work, are consistent with the cryo-electron microscopy model for the run-on activated oligomer of SgrAI bound to DNA.
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Affiliation(s)
- Santosh Shah
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ, 85721, United States of America
| | - Jonathan Sanchez
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ, 85721, United States of America
| | - Andrew Stewart
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ, 85721, United States of America
- Genetics Graduate Program, University of Arizona, Tucson, AZ 85721, United States of America
| | - Michael M. Piperakis
- Department of Chemistry, University of Liverpool, Liverpool, United Kingdom, L69 7ZD, United States of America
| | - Richard Cosstick
- Department of Chemistry, University of Liverpool, Liverpool, United Kingdom, L69 7ZD, United States of America
| | - Claire Nichols
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ, 85721, United States of America
| | - Chad K. Park
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ, 85721, United States of America
| | - Xin Ma
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ, 85721, United States of America
- Department of Chemistry and Biochemistry, Ohio State University, Columbus, OH 43210, United States of America
| | - Vicki Wysocki
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ, 85721, United States of America
- Department of Chemistry and Biochemistry, Ohio State University, Columbus, OH 43210, United States of America
| | - Jurate Bitinaite
- New England Biolabs, Inc., 240 County Road, Ipswich, MA 01938, United States of America
| | - Nancy C. Horton
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ, 85721, United States of America
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12
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Lyumkis D, Talley H, Stewart A, Shah S, Park CK, Tama F, Potter CS, Carragher B, Horton NC. Allosteric regulation of DNA cleavage and sequence-specificity through run-on oligomerization. Structure 2013; 21:1848-58. [PMID: 24055317 PMCID: PMC3898938 DOI: 10.1016/j.str.2013.08.012] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2013] [Revised: 08/08/2013] [Accepted: 08/09/2013] [Indexed: 10/26/2022]
Abstract
SgrAI is a sequence specific DNA endonuclease that functions through an unusual enzymatic mechanism that is allosterically activated 200- to 500-fold by effector DNA, with a concomitant expansion of its DNA sequence specificity. Using single-particle transmission electron microscopy to reconstruct distinct populations of SgrAI oligomers, we show that in the presence of allosteric, activating DNA, the enzyme forms regular, repeating helical structures characterized by the addition of DNA-binding dimeric SgrAI subunits in a run-on manner. We also present the structure of oligomeric SgrAI at 8.6 Å resolution, demonstrating the conformational state of SgrAI in its activated form. Activated and oligomeric SgrAI displays key protein-protein interactions near the helix axis between its N termini, as well as allosteric protein-DNA interactions that are required for enzymatic activation. The hybrid approach reveals an unusual mechanism of enzyme activation that explains SgrAI's oligomerization and allosteric behavior.
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Affiliation(s)
- Dmitry Lyumkis
- National Resource for Automated Molecular Microscopy, The Department of Integrative Structural and Computational Biology, The Scripps Research Institute, La Jolla, CA, 92037
| | - Heather Talley
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ, 85721
| | - Andrew Stewart
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ, 85721
- Genetics Interdisciplinary Graduate Program, University of Arizona, Tucson, AZ, 85721
| | - Santosh Shah
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ, 85721
| | - Chad K. Park
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ, 85721
| | - Florence Tama
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ, 85721
| | - Clinton S. Potter
- National Resource for Automated Molecular Microscopy, The Department of Integrative Structural and Computational Biology, The Scripps Research Institute, La Jolla, CA, 92037
| | - Bridget Carragher
- National Resource for Automated Molecular Microscopy, The Department of Integrative Structural and Computational Biology, The Scripps Research Institute, La Jolla, CA, 92037
| | - Nancy C. Horton
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ, 85721
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Ma X, Shah S, Zhou M, Park CK, Wysocki VH, Horton NC. Structural analysis of activated SgrAI-DNA oligomers using ion mobility mass spectrometry. Biochemistry 2013; 52:4373-81. [PMID: 23742104 DOI: 10.1021/bi3013214] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
SgrAI is a type IIF restriction endonuclease that cuts an unusually long recognition sequence and exhibits self-modulation of DNA cleavage activity and sequence specificity. Previous studies have shown that SgrAI forms large oligomers when bound to particular DNA sequences and under the same conditions where SgrAI exhibits accelerated DNA cleavage kinetics. However, the detailed structure and stoichiometry of the SgrAI-DNA complex as well as the basic building block of the oligomers have not been fully characterized. Ion mobility mass spectrometry (IM-MS) was employed to analyze SgrAI-DNA complexes and show that the basic building block of the oligomers is the DNA-bound SgrAI dimer (DBD) with one SgrAI dimer bound to two precleaved duplex DNA molecules each containing one-half of the SgrAI primary recognition sequence. The oligomers contain variable numbers of DBDs with as many as 19 DBDs. Observation of the large oligomers shows that nanoelectrospray ionization (nano-ESI) can preserve the proposed activated form of an enzyme. Finally, the collision cross section of the SgrAI-DNA oligomers measured by IM-MS was found to have a linear relationship with the number of DBDs in each oligomer, suggesting a regular, repeating structure.
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Affiliation(s)
- Xin Ma
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, Arizona 85721, United States
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14
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Park CK, Stiteler AP, Shah S, Ghare MI, Bitinaite J, Horton NC. Activation of DNA cleavage by oligomerization of DNA-bound SgrAI. Biochemistry 2010; 49:8818-30. [PMID: 20836535 PMCID: PMC2972665 DOI: 10.1021/bi100557v] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
SgrAI is a type II restriction endonuclease that cuts an unusually long recognition sequence and exhibits allosteric self-modulation of DNA activity and sequence specificity. Precleaved primary site DNA has been shown to be an allosteric effector [Hingorani-Varma, K., and Bitinaite, J. (2003) J. Biol. Chem. 278, 40392-40399], stimulating cleavage of both primary (CR|CCGGYG, where the vertical bar indicates a cut site, R denotes A or G, and Y denotes C or T) and secondary [CR|CCGGY(A/C/T) and CR|CCGGGG] site DNA sequences. The fact that DNA is the allosteric effector of this endonuclease suggests at least two DNA binding sites on the functional SgrAI molecule, yet crystal structures of SgrAI [Dunten, P. W., et al. (2008) Nucleic Acids Res. 36, 5405-5416] show only one DNA duplex bound to one dimer of SgrAI. We show that SgrAI forms species larger than dimers or tetramers [high-molecular weight species (HMWS)] in the presence of sufficient concentrations of SgrAI and its primary site DNA sequence that are dependent on the concentration of the DNA-bound SgrAI dimer. Analytical ultracentrifugation indicates that the HMWS is heterogeneous, has sedimentation coefficients of 15-20 s, and is composed of possibly 4-12 DNA-bound SgrAI dimers. SgrAI bound to secondary site DNA will not form HMWS itself but can bind to HMWS formed with primary site DNA and SgrAI. Uncleaved, as well as precleaved, primary site DNA is capable of stimulating HMWS formation. Stimulation of DNA cleavage by SgrAI, at primary as well as secondary sites, is also dependent on the concentration of primary site DNA (cleaved or uncleaved) bound SgrAI dimers. SgrAI bound to secondary site DNA does not have significant stimulatory activity. We propose that the oligomers of DNA-bound SgrAI (i.e., HMWS) are the activated, or activatable, forms of the enzyme.
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Affiliation(s)
- Chad K. Park
- Department of Chemistry & Biochemistry, University of Arizona, Tucson, AZ, 85721
| | - Amanda P. Stiteler
- Department of Chemistry & Biochemistry, University of Arizona, Tucson, AZ, 85721
| | - Santosh Shah
- Department of Chemistry & Biochemistry, University of Arizona, Tucson, AZ, 85721
| | - M. Imran Ghare
- Department of Chemistry & Biochemistry, University of Arizona, Tucson, AZ, 85721
| | | | - Nancy C. Horton
- Department of Chemistry & Biochemistry, University of Arizona, Tucson, AZ, 85721
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