1
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Adams MC, Schiltz CJ, Sun J, Hosford CJ, Johnson VM, Pan H, Borbat PP, Freed JH, Thomason LC, Court C, Court DL, Chappie JS. The crystal structure of bacteriophage λ RexA provides novel insights into the DNA binding properties of Rex-like phage exclusion proteins. Nucleic Acids Res 2024:gkae212. [PMID: 38554102 DOI: 10.1093/nar/gkae212] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2023] [Revised: 03/07/2024] [Accepted: 03/12/2024] [Indexed: 04/01/2024] Open
Abstract
RexA and RexB function as an exclusion system that prevents bacteriophage T4rII mutants from growing on Escherichia coli λ phage lysogens. Recent data established that RexA is a non-specific DNA binding protein that can act independently of RexB to bias the λ bistable switch toward the lytic state, preventing conversion back to lysogeny. The molecular interactions underlying these activities are unknown, owing in part to a dearth of structural information. Here, we present the 2.05-Å crystal structure of the λ RexA dimer, which reveals a two-domain architecture with unexpected structural homology to the recombination-associated protein RdgC. Modelling suggests that our structure adopts a closed conformation and would require significant domain rearrangements to facilitate DNA binding. Mutagenesis coupled with electromobility shift assays, limited proteolysis, and double electron-electron spin resonance spectroscopy support a DNA-dependent conformational change. In vivo phenotypes of RexA mutants suggest that DNA binding is not a strict requirement for phage exclusion but may directly contribute to modulation of the bistable switch. We further demonstrate that RexA homologs from other temperate phages also dimerize and bind DNA in vitro. Collectively, these findings advance our mechanistic understanding of Rex functions and provide new evolutionary insights into different aspects of phage biology.
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Affiliation(s)
- Myfanwy C Adams
- Department of Molecular Medicine, Cornell University, Ithaca, NY 14853, USA
| | - Carl J Schiltz
- Department of Molecular Medicine, Cornell University, Ithaca, NY 14853, USA
| | - Jing Sun
- Department of Molecular Medicine, Cornell University, Ithaca, NY 14853, USA
| | | | - Virginia M Johnson
- Department of Molecular Medicine, Cornell University, Ithaca, NY 14853, USA
| | - Hao Pan
- Department of Molecular Medicine, Cornell University, Ithaca, NY 14853, USA
| | - Peter P Borbat
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14853, USA
- National Biomedical Resource for Advanced Electron Spin Resonance Spectroscopy, Cornell University, Ithaca, NY 14853, USA
| | - Jack H Freed
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14853, USA
- National Biomedical Resource for Advanced Electron Spin Resonance Spectroscopy, Cornell University, Ithaca, NY 14853, USA
| | - Lynn C Thomason
- Center for Cancer Research, National Cancer Institute, Frederick, MD21702, USA
| | - Carolyn Court
- Center for Cancer Research, National Cancer Institute, Frederick, MD21702, USA
| | - Donald L Court
- Center for Cancer Research, National Cancer Institute, Frederick, MD21702, USA
| | - Joshua S Chappie
- Department of Molecular Medicine, Cornell University, Ithaca, NY 14853, USA
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2
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Kennedy MA, Hosford CJ, Azumaya CM, Luyten YA, Chen M, Morgan RD, Stoddard BL. Structures, activity and mechanism of the Type IIS restriction endonuclease PaqCI. Nucleic Acids Res 2023; 51:4467-4487. [PMID: 36987874 PMCID: PMC10201449 DOI: 10.1093/nar/gkad228] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2022] [Revised: 03/10/2023] [Accepted: 03/16/2023] [Indexed: 03/30/2023] Open
Abstract
Type IIS restriction endonucleases contain separate DNA recognition and catalytic domains and cleave their substrates at well-defined distances outside their target sequences. They are employed in biotechnology for a variety of purposes, including the creation of gene-targeting zinc finger and TAL effector nucleases and DNA synthesis applications such as Golden Gate assembly. The most thoroughly studied Type IIS enzyme, FokI, has been shown to require multimerization and engagement with multiple DNA targets for optimal cleavage activity; however, details of how it or similar enzymes forms a DNA-bound reaction complex have not been described at atomic resolution. Here we describe biochemical analyses of DNA cleavage by the Type IIS PaqCI restriction endonuclease and a series of molecular structures in the presence and absence of multiple bound DNA targets. The enzyme displays a similar tetrameric organization of target recognition domains in the absence or presence of bound substrate, with a significant repositioning of endonuclease domains in a trapped DNA-bound complex that is poised to deliver the first of a series of double-strand breaks. PaqCI and FokI share similar structural mechanisms of DNA cleavage, but considerable differences in their domain organization and quaternary architecture, facilitating comparisons between distinct Type IIS enzymes.
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Affiliation(s)
- Madison A Kennedy
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, 1100 Fairview Ave. North, Seattle,WA 98109, USA
| | | | - Caleigh M Azumaya
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, 1100 Fairview Ave. North, Seattle,WA 98109, USA
| | - Yvette A Luyten
- New England Biolabs, 240 County Road, Ipswich, MA 01938, USA
| | - Minyong Chen
- New England Biolabs, 240 County Road, Ipswich, MA 01938, USA
| | | | - Barry L Stoddard
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, 1100 Fairview Ave. North, Seattle,WA 98109, USA
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3
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Schiltz CJ, Wilson JR, Hosford CJ, Adams MC, Preising SE, DeBlasio SL, MacLeod HJ, Van Eck J, Heck ML, Chappie JS. Polerovirus N-terminal readthrough domain structures reveal molecular strategies for mitigating virus transmission by aphids. Nat Commun 2022; 13:6368. [PMID: 36289207 PMCID: PMC9606263 DOI: 10.1038/s41467-022-33979-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2022] [Accepted: 10/10/2022] [Indexed: 12/25/2022] Open
Abstract
Poleroviruses, enamoviruses, and luteoviruses are icosahedral, positive sense RNA viruses that cause economically important diseases in food and fiber crops. They are transmitted by phloem-feeding aphids in a circulative manner that involves the movement across and within insect tissues. The N-terminal portion of the viral readthrough domain (NRTD) has been implicated as a key determinant of aphid transmission in each of these genera. Here, we report crystal structures of the NRTDs from the poleroviruses turnip yellow virus (TuYV) and potato leafroll virus (PLRV) at 1.53-Å and 2.22-Å resolution, respectively. These adopt a two-domain arrangement with a unique interdigitated topology and form highly conserved dimers that are stabilized by a C-terminal peptide that is critical for proper folding. We demonstrate that the PLRV NRTD can act as an inhibitor of virus transmission and identify NRTD mutant variants that are lethal to aphids. Sequence conservation argues that enamovirus and luteovirus NRTDs will follow the same structural blueprint, which affords a biological approach to block the spread of these agricultural pathogens in a generalizable manner.
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Affiliation(s)
- Carl J. Schiltz
- grid.5386.8000000041936877XDepartment of Molecular Medicine, Cornell University, Ithaca, NY 14853 USA ,grid.152326.10000 0001 2264 7217Present Address: Department of Biological Sciences, Vanderbilt University, Nashville, TN 37232 USA
| | - Jennifer R. Wilson
- grid.5386.8000000041936877XSection of Plant Pathology and Plant-Microbe Biology, School of Integrative Plant Sciences, Cornell University, Ithaca, NY 14853 USA ,grid.508983.fPresent Address: USDA-Agricultural Research Service, Corn, Soybean & Wheat Quality Research Unit, Wooster, OH 44691 USA
| | - Christopher J. Hosford
- grid.5386.8000000041936877XDepartment of Molecular Medicine, Cornell University, Ithaca, NY 14853 USA ,Present Address: LifeMine Therapeutics, Cambridge, MA 02140 USA
| | - Myfanwy C. Adams
- grid.5386.8000000041936877XDepartment of Molecular Medicine, Cornell University, Ithaca, NY 14853 USA
| | - Stephanie E. Preising
- grid.5386.8000000041936877XSection of Plant Pathology and Plant-Microbe Biology, School of Integrative Plant Sciences, Cornell University, Ithaca, NY 14853 USA
| | - Stacy L. DeBlasio
- grid.5386.8000000041936877XSection of Plant Pathology and Plant-Microbe Biology, School of Integrative Plant Sciences, Cornell University, Ithaca, NY 14853 USA ,grid.508984.8USDA-Agricultural Research Service, Emerging Pest and Pathogen Research Unit, Ithaca, NY 14853 USA
| | - Hannah J. MacLeod
- grid.508984.8USDA-Agricultural Research Service, Emerging Pest and Pathogen Research Unit, Ithaca, NY 14853 USA ,Present Address: Accelevir Diagnostics, Baltimore, MD 21202 USA
| | - Joyce Van Eck
- grid.5386.8000000041936877XSection of Plant Breeding and Genetics, School of Integrative Plant Sciences, Cornell University, Ithaca, NY 14853 USA ,grid.5386.8000000041936877XBoyce Thompson Institute for Plant Research, Ithaca, NY 14853 USA
| | - Michelle L. Heck
- grid.5386.8000000041936877XSection of Plant Pathology and Plant-Microbe Biology, School of Integrative Plant Sciences, Cornell University, Ithaca, NY 14853 USA ,grid.508984.8USDA-Agricultural Research Service, Emerging Pest and Pathogen Research Unit, Ithaca, NY 14853 USA ,grid.5386.8000000041936877XBoyce Thompson Institute for Plant Research, Ithaca, NY 14853 USA
| | - Joshua S. Chappie
- grid.5386.8000000041936877XDepartment of Molecular Medicine, Cornell University, Ithaca, NY 14853 USA
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4
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Thomason LC, Schiltz CJ, Court C, Hosford CJ, Adams MC, Chappie JS, Court DL. Bacteriophage λ RexA and RexB Functions Assist the Transition from Lysogeny to Lytic Growth. Mol Microbiol 2021; 116:1044-1063. [PMID: 34379857 DOI: 10.1111/mmi.14792] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2021] [Revised: 08/04/2021] [Accepted: 08/06/2021] [Indexed: 11/26/2022]
Abstract
The CI and Cro repressors of bacteriophage λ create a bistable switch between lysogenic and lytic growth. In λ lysogens, CI repressor expressed from the PRM promoter blocks expression of the lytic promoters PL and PR to allow stable maintenance of the lysogenic state. When lysogens are induced, CI repressor is inactivated and Cro repressor is expressed from the lytic PR promoter. Cro repressor blocks PRM transcription and CI repressor synthesis to ensure that the lytic state proceeds. RexA and RexB proteins, like CI, are expressed from the PRM promoter in λ lysogens; RexB is also expressed from a second promoter, PLIT , embedded in rexA. Here we show that RexA binds CI repressor and assists the transition from lysogenic to lytic growth, using both intact lysogens and defective prophages with reporter genes under control of the lytic PL and PR promoters. Once lytic growth begins, if the bistable switch does return to the immune state, RexA expression lessens the probability that it will remain there, thus stabilizing the lytic state and activation of the lytic PL and PR promoters. RexB modulates the effect of RexA and may also help establish phage DNA replication as lytic growth ensues.
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Affiliation(s)
- Lynn C Thomason
- Basic Science Program, Frederick National Laboratory for Cancer Research, Frederick, 21702.,RNA Biology Laboratory, National Cancer Institute/Frederick Cancer Research and Development Center, Frederick, 21702
| | - Carl J Schiltz
- Department of Molecular Medicine, Cornell University, Ithaca, 14850.,Department of Biological Sciences and Center for Structural Biology, Vanderbilt University, Nashville, TN, 37232, USA
| | - Carolyn Court
- RNA Biology Laboratory, National Cancer Institute/Frederick Cancer Research and Development Center, Frederick, 21702
| | - Christopher J Hosford
- Department of Molecular Medicine, Cornell University, Ithaca, 14850.,New England Biolabs, Inc, Ipswich, MA, USA
| | - Myfanwy C Adams
- Department of Molecular Medicine, Cornell University, Ithaca, 14850
| | - Joshua S Chappie
- Department of Molecular Medicine, Cornell University, Ithaca, 14850
| | - Donald L Court
- RNA Biology Laboratory, National Cancer Institute/Frederick Cancer Research and Development Center, Frederick, 21702
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5
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Niu Y, Suzuki H, Hosford CJ, Walz T, Chappie JS. Structural asymmetry governs the assembly and GTPase activity of McrBC restriction complexes. Nat Commun 2020; 11:5907. [PMID: 33219217 PMCID: PMC7680126 DOI: 10.1038/s41467-020-19735-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2020] [Accepted: 10/26/2020] [Indexed: 01/21/2023] Open
Abstract
McrBC complexes are motor-driven nucleases functioning in bacterial self-defense by cleaving foreign DNA. The GTP-specific AAA + protein McrB powers translocation along DNA and its hydrolysis activity is stimulated by its partner nuclease McrC. Here, we report cryo-EM structures of Thermococcus gammatolerans McrB and McrBC, and E. coli McrBC. The McrB hexamers, containing the necessary catalytic machinery for basal GTP hydrolysis, are intrinsically asymmetric. This asymmetry directs McrC binding so that it engages a single active site, where it then uses an arginine/lysine-mediated hydrogen-bonding network to reposition the asparagine in the McrB signature motif for optimal catalytic function. While the two McrBC complexes use different DNA-binding domains, these contribute to the same general GTP-recognition mechanism employed by all G proteins. Asymmetry also induces distinct inter-subunit interactions around the ring, suggesting a coordinated and directional GTP-hydrolysis cycle. Our data provide insights into the conserved molecular mechanisms governing McrB family AAA + motors. The bacterial defense system McrBC is a two-component motor-driven nuclease complex that cleaves foreign DNA. Here, the authors present the structures of the GTP-specific AAA + motor protein McrB and two McrBC complexes and discuss the molecular mechanism of how McrC binding stimulates McrB GTP hydrolysis.
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Affiliation(s)
- Yiming Niu
- Department of Molecular Medicine, Cornell University, Ithaca, NY, USA.,Laboratory of Molecular Electron Microscopy, The Rockefeller University, New York, NY, USA.,Laboratory Molecular Neurobiology and Biophysics, The Rockefeller University, New York, NY, USA
| | - Hiroshi Suzuki
- Laboratory of Molecular Electron Microscopy, The Rockefeller University, New York, NY, USA.,Advanced Research Institute, Tokyo Medical and Dental University, Tokyo, Japan
| | - Christopher J Hosford
- Department of Molecular Medicine, Cornell University, Ithaca, NY, USA.,New England Biolabs, Inc., Ipswich, MA, USA
| | - Thomas Walz
- Laboratory of Molecular Electron Microscopy, The Rockefeller University, New York, NY, USA.
| | - Joshua S Chappie
- Department of Molecular Medicine, Cornell University, Ithaca, NY, USA.
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6
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Hosford CJ, Adams MC, Niu Y, Chappie JS. The N-terminal domain of Staphylothermus marinus McrB shares structural homology with PUA-like RNA binding proteins. J Struct Biol 2020; 211:107572. [PMID: 32652237 DOI: 10.1016/j.jsb.2020.107572] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2019] [Revised: 07/01/2020] [Accepted: 07/02/2020] [Indexed: 12/27/2022]
Abstract
McrBC is a conserved modification-dependent restriction system that in Escherichia coli specifically targets foreign DNA containing methylated cytosines. Crystallographic data show that the N-terminal domain of Escherichia coli McrB binds substrates via a base flipping mechanism. This region is poorly conserved among the plethora of McrB homologs, suggesting that other species may use alternative binding strategies and/or recognize different targets. Here we present the crystal structure of the N-terminal domain from Stayphlothermus marinus McrB (Sm3-180) at 1.92 Å, which adopts a PUA-like EVE fold that is closely related to the YTH and ASCH RNA binding domains. Unlike most PUA-like domains, Sm3-180 binds DNA and can associate with different modified substrates. We find the canonical 'aromatic cage' binding pocket that confers specificity for methylated bases in other EVE/YTH domains is degenerate and occluded in Sm3-180, which may contribute to its promiscuity in target recognition. Further structural comparison between different PUA-like domains identifies motifs and conformational variations that correlate with the preference for binding either DNA or RNA. Together these data have important implications for PUA-like domain specificity and suggest a broader biological versatility for the McrBC family than previously described.
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Affiliation(s)
| | - Myfanwy C Adams
- Department of Molecular Medicine, Cornell University, Ithaca, NY 14853, USA
| | - Yiming Niu
- Department of Molecular Medicine, Cornell University, Ithaca, NY 14853, USA
| | - Joshua S Chappie
- Department of Molecular Medicine, Cornell University, Ithaca, NY 14853, USA.
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7
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Tornabene BA, Varlakhanova NV, Hosford CJ, Chappie JS, Ford MGJ. Structural and functional characterization of the dominant negative P-loop lysine mutation in the dynamin superfamily protein Vps1. Protein Sci 2020; 29:1416-1428. [PMID: 31981262 DOI: 10.1002/pro.3830] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2019] [Revised: 01/16/2020] [Accepted: 01/16/2020] [Indexed: 12/15/2022]
Abstract
Dynamin-superfamily proteins (DSPs) are large self-assembling mechanochemical GTPases that harness GTP hydrolysis to drive membrane remodeling events needed for many cellular processes. Mutation to alanine of a fully conserved lysine within the P-loop of the DSP GTPase domain results in abrogation of GTPase activity. This mutant has been widely used in the context of several DSPs as a dominant-negative to impair DSP-dependent processes. However, the precise deficit of the P-loop K to A mutation remains an open question. Here, we use biophysical, biochemical and structural approaches to characterize this mutant in the context of the endosomal DSP Vps1. We show that the Vps1 P-loop K to A mutant binds nucleotide with an affinity similar to wild type but exhibits defects in the organization of the GTPase active site that explain the lack of hydrolysis. In cells, Vps1 and Dnm1 bearing the P-loop K to A mutation are defective in disassembly. These mutants become trapped in assemblies at the typical site of action of the DSP. This work provides mechanistic insight into the widely-used DSP P-loop K to A mutation and the basis of its dominant-negative effects in the cell.
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Affiliation(s)
- Bryan A Tornabene
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Natalia V Varlakhanova
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | | | - Joshua S Chappie
- Department of Molecular Medicine, Cornell University, Ithaca, New York
| | - Marijn G J Ford
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
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8
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Hosford CJ, Bui AQ, Chappie JS. The structure of the Thermococcus gammatolerans McrB N-terminal domain reveals a new mode of substrate recognition and specificity among McrB homologs. J Biol Chem 2020. [DOI: 10.1016/s0021-9258(17)49932-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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9
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Hosford CJ, Bui AQ, Chappie JS. The structure of the Thermococcus gammatolerans McrB N-terminal domain reveals a new mode of substrate recognition and specificity among McrB homologs. J Biol Chem 2019; 295:743-756. [PMID: 31822563 DOI: 10.1074/jbc.ra119.010188] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2019] [Revised: 12/07/2019] [Indexed: 01/12/2023] Open
Abstract
McrBC is a two-component, modification-dependent restriction system that cleaves foreign DNA-containing methylated cytosines. Previous crystallographic studies have shown that Escherichia coli McrB uses a base-flipping mechanism to recognize these modified substrates with high affinity. The side chains stabilizing both the flipped base and the distorted duplex are poorly conserved among McrB homologs, suggesting that other mechanisms may exist for binding modified DNA. Here we present the structures of the Thermococcus gammatolerans McrB DNA-binding domain (TgΔ185) both alone and in complex with a methylated DNA substrate at 1.68 and 2.27 Å resolution, respectively. The structures reveal that TgΔ185 consists of a YT521-B homology (YTH) domain, which is commonly found in eukaryotic proteins that bind methylated RNA and is structurally unrelated to the E. coli McrB DNA-binding domain. Structural superposition and co-crystallization further show that TgΔ185 shares a conserved aromatic cage with other YTH domains, which forms the binding pocket for a flipped-out base. Mutational analysis of this aromatic cage supports its role in conferring specificity for the methylated adenines, whereas an extended basic surface present in TgΔ185 facilitates its preferential binding to duplex DNA rather than RNA. Together, these findings establish a new binding mode and specificity among McrB homologs and expand the biological roles of YTH domains.
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Affiliation(s)
| | - Anthony Q Bui
- Department of Molecular Medicine, Cornell University, Ithaca, New York 14853
| | - Joshua S Chappie
- Department of Molecular Medicine, Cornell University, Ithaca, New York 14853
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10
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Schiltz CJ, Lee A, Partlow EA, Hosford CJ, Chappie JS. Structural characterization of Class 2 OLD family nucleases supports a two-metal catalysis mechanism for cleavage. Nucleic Acids Res 2019; 47:9448-9463. [PMID: 31400118 PMCID: PMC6755086 DOI: 10.1093/nar/gkz703] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2019] [Revised: 07/29/2019] [Accepted: 07/31/2019] [Indexed: 12/18/2022] Open
Abstract
Overcoming lysogenization defect (OLD) proteins constitute a family of uncharacterized nucleases present in bacteria, archaea, and some viruses. These enzymes contain an N-terminal ATPase domain and a C-terminal Toprim domain common amongst replication, recombination, and repair proteins. The in vivo activities of OLD proteins remain poorly understood and no definitive structural information exists. Here we identify and define two classes of OLD proteins based on differences in gene neighborhood and amino acid sequence conservation and present the crystal structures of the catalytic C-terminal regions from the Burkholderia pseudomallei and Xanthamonas campestris p.v. campestris Class 2 OLD proteins at 2.24 Å and 1.86 Å resolution respectively. The structures reveal a two-domain architecture containing a Toprim domain with altered architecture and a unique helical domain. Conserved side chains contributed by both domains coordinate two bound magnesium ions in the active site of B. pseudomallei OLD in a geometry that supports a two-metal catalysis mechanism for cleavage. The spatial organization of these domains additionally suggests a novel mode of DNA binding that is distinct from other Toprim containing proteins. Together, these findings define the fundamental structural properties of the OLD family catalytic core and the underlying mechanism controlling nuclease activity.
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Affiliation(s)
- Carl J Schiltz
- Department of Molecular Medicine, Cornell University, Ithaca, NY 14853, USA
| | - April Lee
- Department of Molecular Medicine, Cornell University, Ithaca, NY 14853, USA
| | - Edward A Partlow
- Department of Molecular Medicine, Cornell University, Ithaca, NY 14853, USA
| | | | - Joshua S Chappie
- Department of Molecular Medicine, Cornell University, Ithaca, NY 14853, USA
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11
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Varlakhanova NV, Alvarez FJD, Brady TM, Tornabene BA, Hosford CJ, Chappie JS, Zhang P, Ford MGJ. Structures of the fungal dynamin-related protein Vps1 reveal a unique, open helical architecture. J Cell Biol 2018; 217:3608-3624. [PMID: 30087125 PMCID: PMC6168280 DOI: 10.1083/jcb.201712021] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2017] [Revised: 05/26/2018] [Accepted: 07/17/2018] [Indexed: 12/19/2022] Open
Abstract
How specific dynamin-related proteins (DRPs) are tailored to their cellular targets is an open question. Varlakhanova et al. present structures of the fungal DRP Vps1, which functions at the endosomal compartment. The crystal and cryoEM structures reveal a unique DRP architecture that highlights structural flexibilities of DRP self-assembly. Dynamin-related proteins (DRPs) are large multidomain GTPases required for diverse membrane-remodeling events. DRPs self-assemble into helical structures, but how these structures are tailored to their cellular targets remains unclear. We demonstrate that the fungal DRP Vps1 primarily localizes to and functions at the endosomal compartment. We present crystal structures of a Vps1 GTPase–bundle signaling element (BSE) fusion in different nucleotide states to capture GTP hydrolysis intermediates and concomitant conformational changes. Using cryoEM, we determined the structure of full-length GMPPCP-bound Vps1. The Vps1 helix is more open and flexible than that of dynamin. This is due to further opening of the BSEs away from the GTPase domains. A novel interface between adjacent GTPase domains forms in Vps1 instead of the contacts between the BSE and adjacent stalks and GTPase domains as seen in dynamin. Disruption of this interface abolishes Vps1 function in vivo. Hence, Vps1 exhibits a unique helical architecture, highlighting structural flexibilities of DRP self-assembly.
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Affiliation(s)
| | - Frances J D Alvarez
- Department of Structural Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA
| | - Tyler M Brady
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA
| | - Bryan A Tornabene
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA
| | | | - Joshua S Chappie
- Department of Molecular Medicine, Cornell University, Ithaca, NY
| | - Peijun Zhang
- Department of Structural Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA.,Division of Structural Biology, Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, UK.,Electron Bio-Imaging Centre, Diamond Light Source, Harwell Science and Innovation Campus, Didcot, UK
| | - Marijn G J Ford
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA
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12
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Hosford CJ, Chappie JS. The crystal structure of the Helicobacter pylori LlaJI.R1 N-terminal domain provides a model for site-specific DNA binding. J Biol Chem 2018; 293:11758-11771. [PMID: 29895618 PMCID: PMC6066307 DOI: 10.1074/jbc.ra118.001888] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2018] [Revised: 06/04/2018] [Indexed: 12/11/2022] Open
Abstract
Restriction modification systems consist of an endonuclease that cleaves foreign DNA site-specifically and an associated methyltransferase that protects the corresponding target site in the host genome. Modification-dependent restriction systems, in contrast, specifically recognize and cleave methylated and/or glucosylated DNA. The LlaJI restriction system contains two 5-methylcytosine (5mC) methyltransferases (LlaJI.M1 and LlaJI.M2) and two restriction proteins (LlaJI.R1 and LlaJI.R2). LlaJI.R1 and LlaJI.R2 are homologs of McrB and McrC, respectively, which in Escherichia coli function together as a modification-dependent restriction complex specific for 5mC-containing DNA. Lactococcus lactis LlaJI.R1 binds DNA site-specifically, suggesting that the LlaJI system uses a different mode of substrate recognition. Here we present the structure of the N-terminal DNA-binding domain of Helicobacter pylori LlaJI.R1 at 1.97-Å resolution, which adopts a B3 domain fold. Structural comparison to B3 domains in plant transcription factors and other restriction enzymes identifies key recognition motifs responsible for site-specific DNA binding. Moreover, biochemistry and structural modeling provide a rationale for how H. pylori LlaJI.R1 may bind a target site that differs from the 5-bp sequence recognized by other LlaJI homologs and identify residues critical for this recognition activity. These findings underscore the inherent structural plasticity of B3 domains, allowing recognition of a variety of substrates using the same structural core.
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Affiliation(s)
- Christopher J Hosford
- From the Department of Molecular Medicine, Cornell University, Ithaca, New York 14853
| | - Joshua S Chappie
- From the Department of Molecular Medicine, Cornell University, Ithaca, New York 14853
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