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Li H, Hwang Y, Perry K, Bushman F, Van Duyne GD. Structure and Metal Binding Properties of a Poxvirus Resolvase. J Biol Chem 2016; 291:11094-104. [PMID: 27013661 DOI: 10.1074/jbc.m115.709139] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2015] [Indexed: 11/06/2022] Open
Abstract
Poxviruses replicate their linear genomes by forming concatemers that must be resolved into monomeric units to produce new virions. A viral resolvase cleaves DNA four-way junctions extruded at the concatemer junctions to produce monomeric genomes. This cleavage reaction is required for viral replication, so the resolvase is an attractive target for small molecule inhibitors. To provide a platform for understanding resolvase mechanism and designing inhibitors, we have determined the crystal structure of the canarypox virus (CPV) resolvase. CPV resolvase is dimer of RNase H superfamily domains related to Escherichia coli RuvC, with an active site lined by highly conserved acidic residues that bind metal ions. There are several intriguing structural differences between resolvase and RuvC, and a model of the CPV resolvase·Holliday junction complex provides insights into the consequences of these differences, including a plausible explanation for the weak sequence specificity exhibited by the poxvirus enzymes. The model also explains why the poxvirus resolvases are more promiscuous than RuvC, cleaving a variety of branched, bulged, and flap-containing substrates. Based on the unique active site structure observed for CPV resolvase, we have carried out a series of experiments to test divalent ion usage and preferences. We find that the two resolvase metal binding sites have different preferences for Mg(2+) versus Mn(2+) Optimal resolvase activity is maintained with 5 μm Mn(2+) and 100 μm Mg(2+), concentrations that are well below those required for either metal alone. Together, our findings provide biochemical insights and structural models that will facilitate studying poxvirus replication and the search for efficient poxvirus inhibitors.
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Affiliation(s)
- Huiguang Li
- From the Department of Biochemistry & Biophysics, the Graduate Group in Biochemistry and Molecular Biophysics, and
| | - Young Hwang
- the Department of Microbiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104
| | - Kay Perry
- the Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14850, and the Argonne National Laboratory, Argonne, Illinois 60439
| | - Frederic Bushman
- the Department of Microbiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104,
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2
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Moiseeva ED, Bazhulina NP, Gursky YG, Grokhovsky SL, Surovaya AN, Gursky GV. Targeting Holliday junctions by origin DNA-binding protein of herpes simplex virus type 1. J Biomol Struct Dyn 2016; 35:704-723. [PMID: 26987269 DOI: 10.1080/07391102.2016.1161561] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
In the present paper, the interactions of the origin binding protein (OBP) of herpes simplex virus type 1 (HSV1) with synthetic four-way Holliday junctions (HJs) were studied using electrophoresis mobility shift assay and the FRET method and compared with the interactions of the protein with duplex and single-stranded DNAs. It has been found that OBP exhibits a strong preference for binding to four-way and three-way DNA junctions and possesses much lower affinities to duplex and single-stranded DNAs. The protein forms three types of complexes with HJs. It forms complexes I and II which are reminiscent of the tetramer and octamer complexes with four-way junction of HJ-specific protein RuvA of Escherichia coli. The binding approaches saturation level when two OBP dimers are bound per junction. In the presence of Mg2+ ions (≥2 mM) OBP also interacts with HJ in the stacked arm form (complex III). In the presence of 5 mM ATP and 10 mM Mg2+ ions OBP catalyzes processing of the HJ in which one of the annealed oligonucleotides has a 3'-terminal tail containing 20 unpaired thymine residues. The observed preference of OBP for binding to the four-way DNA junctions provides a basis for suggestion that OBP induces large DNA structural changes upon binding to Box I and Box II sites in OriS. These changes involve the bending and partial melting of the DNA at A+T-rich spacer and also include the formation of HJ containing Box I and Box II inverted repeats and flanking DNA sequences.
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Affiliation(s)
- E D Moiseeva
- a Engelhardt Institute of Molecular Biology , Russian Academy of Sciences , ul. Vavilova 32, 119991 Moscow , Russia
| | - N P Bazhulina
- a Engelhardt Institute of Molecular Biology , Russian Academy of Sciences , ul. Vavilova 32, 119991 Moscow , Russia
| | - Y G Gursky
- b Russian Cardiology Research-and-Production Complex , 3ya Cherepkovskaya ul. 15a, 121552 Moscow , Russia
| | - S L Grokhovsky
- a Engelhardt Institute of Molecular Biology , Russian Academy of Sciences , ul. Vavilova 32, 119991 Moscow , Russia
| | - A N Surovaya
- a Engelhardt Institute of Molecular Biology , Russian Academy of Sciences , ul. Vavilova 32, 119991 Moscow , Russia
| | - G V Gursky
- a Engelhardt Institute of Molecular Biology , Russian Academy of Sciences , ul. Vavilova 32, 119991 Moscow , Russia
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3
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Kinetic analysis of product release and metal ions in a metallonuclease. Arch Biochem Biophys 2009; 483:1-9. [PMID: 19161971 DOI: 10.1016/j.abb.2009.01.001] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2008] [Revised: 01/02/2009] [Accepted: 01/05/2009] [Indexed: 10/21/2022]
Abstract
Most nucleases rely on divalent cations as cofactors to catalyze the hydrolysis of nucleic acid phosphodiester bonds. Here both equilibrium and kinetic experiments are used to test recently proposed models regarding the metal ion dependence of product release and the degree of cooperativity between metal ions bound in the active sites of the homodimeric PvuII endonuclease. Equilibrium fluorescence anisotropy studies indicate that product binding is dramatically weakened in the presence of metal ions. Pre-steady state kinetics indicate that product release is at least partially rate limiting. Steady state and pre-steady state data fit best to models in which metals remain bound to the enzyme after the release of product. Finally, analysis of cooperative and independent binding models for metal ions indicates that single turnover kinetic data are consistent with little to no positive cooperativity between the two metal ions binding each active site.
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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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5
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Hadden JM, Déclais AC, Phillips SE, Lilley DM. Metal ions bound at the active site of the junction-resolving enzyme T7 endonuclease I. EMBO J 2002; 21:3505-15. [PMID: 12093751 PMCID: PMC126086 DOI: 10.1093/emboj/cdf337] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
T7 endonuclease I is a nuclease that is selective for the structure of the four-way DNA junction. The active site is similar to those of a number of restriction enzymes. We have solved the crystal structure of endonuclease I with a wild-type active site. Diffusion of manganese ions into the crystal revealed two peaks of electron density per active site, defining two metal ion-binding sites. Site 1 is fully occupied, and the manganese ion is coordinated by the carboxylate groups of Asp55 and Glu65, and the main chain carbonyl of Thr66. Site 2 is partially occupied, and the metal ion has a single protein ligand, the remaining carboxylate oxygen atom of Asp55. Isothermal titration calorimetry showed the sequential exothermic binding of two manganese ions in solution, with dissociation constants of 0.58 +/- 0.019 and 14 +/- 1.5 mM. These results are consistent with a two metal ion mechanism for the cleavage reaction, in which the hydrolytic water molecule is contained in the first coordination sphere of the site 1-bound metal ion.
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Affiliation(s)
| | - Anne-Cécile Déclais
- Astbury Centre for Structural Molecular Biology, School of Biochemistry and Molecular Biology, University of Leeds, Leeds LS2 9JT and
Cancer Research UK Nucleic Acid Structure Research Group, Department of Biochemistry, MSI/WTB Complex, The University of Dundee, Dundee DD1 5EH, UK Corresponding author e-mail:
| | | | - David M.J. Lilley
- Astbury Centre for Structural Molecular Biology, School of Biochemistry and Molecular Biology, University of Leeds, Leeds LS2 9JT and
Cancer Research UK Nucleic Acid Structure Research Group, Department of Biochemistry, MSI/WTB Complex, The University of Dundee, Dundee DD1 5EH, UK Corresponding author e-mail:
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Kvaratskhelia M, Wardleworth BN, Bond CS, Fogg JM, Lilley DMJ, White MF. Holliday junction resolution is modulated by archaeal chromatin components in vitro. J Biol Chem 2002; 277:2992-6. [PMID: 11709558 DOI: 10.1074/jbc.m109496200] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The Holliday junction-resolving enzyme Hjc is conserved in the archaea and probably plays a role analogous to that of Escherichia coli RuvC in the pathway of homologous recombination. Hjc specifically recognizes four-way DNA junctions, cleaving them without sequence preference to generate recombinant DNA duplex products. Hjc imposes an X-shaped global conformation on the bound DNA junction and distorts base stacking around the point of cleavage, three nucleotides 3' of the junction center. We show that Hjc is autoinhibitory under single turnover assay conditions and that this can be relieved by the addition of either competitor duplex DNA or the architectural double-stranded DNA-binding protein Sso7d (i.e. by approximating in vivo conditions more closely). Using a combination of isothermal titration calorimetry and fluorescent resonance energy transfer, we demonstrate that multiple Hjc dimers can bind to each synthetic four-way junction and provide evidence for significant distortion of the junction structure at high protein:DNA ratios. Analysis of crystal packing interactions in the crystal structure of Hjc suggests a molecular basis for this autoinhibition. The wider implications of these findings for the quantitative study of DNA-protein interactions is discussed.
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Affiliation(s)
- Mamuka Kvaratskhelia
- Centre for Biomolecular Science, University of Saint Andrews, North Haugh, Saint Andrews, KY16 9ST, United Kingdom
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7
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Bassi GS, de Oliveira DM, White MF, Weeks KM. Recruitment of intron-encoded and co-opted proteins in splicing of the bI3 group I intron RNA. Proc Natl Acad Sci U S A 2002; 99:128-33. [PMID: 11773622 PMCID: PMC117526 DOI: 10.1073/pnas.012579299] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2001] [Indexed: 11/18/2022] Open
Abstract
Detectable splicing by the Saccharomyces cerevisiae mitochondrial bI3 group I intron RNA in vitro is shown to require both an intron-encoded protein, the bI3 maturase, and the nuclear-encoded protein, Mrs1. Both proteins bind independently to the bI3 RNA. The bI3 maturase binds as a monomer, whereas Mrs1 is a dimer in solution that assembles as two dimers, cooperatively, on the RNA. The active six-subunit complex has a molecular mass of 420 kDa, splices with a k(cat) of 0.3 min(-1), and binds the guanosine nucleophile with an affinity comparable to other group I introns. The functional bI3 maturase domain is translated from within the RNA that encodes the intron, has evolved a high-affinity RNA-binding activity, and is a member of the LAGLIDADG family of DNA endonucleases, but appears to have lost DNA cleavage activity. Mrs1 is a divergent member of the RNase H fold superfamily of dimeric DNA junction-resolving enzymes that also appears to have lost its nuclease activity and now functions as a tetramer in RNA binding. Thus, the bI3 ribonucleoprotein is the product of a process in which a once-catalytically active RNA now obligatorily requires two facilitating protein cofactors, both of which are compromised in their original functions.
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Affiliation(s)
- Gurminder S Bassi
- Department of Chemistry, University of North Carolina, Chapel Hill, NC 27599-3290, USA
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8
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Ceschini S, Keeley A, McAlister MS, Oram M, Phelan J, Pearl LH, Tsaneva IR, Barrett TE. Crystal structure of the fission yeast mitochondrial Holliday junction resolvase Ydc2. EMBO J 2001; 20:6601-11. [PMID: 11726496 PMCID: PMC125760 DOI: 10.1093/emboj/20.23.6601] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Resolution of Holliday junctions into separate DNA duplexes requires enzymatic cleavage of an equivalent strand from each contributing duplex at or close to the point of strand exchange. Diverse Holliday junction-resolving enzymes have been identified in bacteria, bacteriophages, archaea and pox viruses, but the only eukaryotic examples identified so far are those from fungal mitochondria. We have now determined the crystal structure of Ydc2 (also known as SpCce1), a Holliday junction resolvase from the fission yeast Schizosaccharomyces pombe that is involved in the maintenance of mitochondrial DNA. This first structure of a eukaryotic Holliday junction resolvase confirms a distant evolutionary relationship to the bacterial RuvC family, but reveals structural features which are unique to the eukaryotic enzymes. Detailed analysis of the dimeric structure suggests mechanisms for junction isomerization and communication between the two active sites, and together with site-directed mutagenesis identifies residues involved in catalysis.
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Affiliation(s)
| | - Anthony Keeley
- Section of Structural Biology, Institute of Cancer Research, Chester Beatty Laboratories, 237 Fulham Road, London SW3 6JB,
Department of Biochemistry and Molecular Biology, University College London, Gower Street, London WC1E 6BT, Department of Crystallography and BBSRC Bloomsbury Centre for Structural Biology, Birkbeck College, Malet Street, London WC1E 7HX, UK Corresponding author e-mail:
| | - Mark S.B. McAlister
- Section of Structural Biology, Institute of Cancer Research, Chester Beatty Laboratories, 237 Fulham Road, London SW3 6JB,
Department of Biochemistry and Molecular Biology, University College London, Gower Street, London WC1E 6BT, Department of Crystallography and BBSRC Bloomsbury Centre for Structural Biology, Birkbeck College, Malet Street, London WC1E 7HX, UK Corresponding author e-mail:
| | - Mark Oram
- Section of Structural Biology, Institute of Cancer Research, Chester Beatty Laboratories, 237 Fulham Road, London SW3 6JB,
Department of Biochemistry and Molecular Biology, University College London, Gower Street, London WC1E 6BT, Department of Crystallography and BBSRC Bloomsbury Centre for Structural Biology, Birkbeck College, Malet Street, London WC1E 7HX, UK Corresponding author e-mail:
| | - John Phelan
- Section of Structural Biology, Institute of Cancer Research, Chester Beatty Laboratories, 237 Fulham Road, London SW3 6JB,
Department of Biochemistry and Molecular Biology, University College London, Gower Street, London WC1E 6BT, Department of Crystallography and BBSRC Bloomsbury Centre for Structural Biology, Birkbeck College, Malet Street, London WC1E 7HX, UK Corresponding author e-mail:
| | | | - Irina R. Tsaneva
- Section of Structural Biology, Institute of Cancer Research, Chester Beatty Laboratories, 237 Fulham Road, London SW3 6JB,
Department of Biochemistry and Molecular Biology, University College London, Gower Street, London WC1E 6BT, Department of Crystallography and BBSRC Bloomsbury Centre for Structural Biology, Birkbeck College, Malet Street, London WC1E 7HX, UK Corresponding author e-mail:
| | - Tracey E. Barrett
- Section of Structural Biology, Institute of Cancer Research, Chester Beatty Laboratories, 237 Fulham Road, London SW3 6JB,
Department of Biochemistry and Molecular Biology, University College London, Gower Street, London WC1E 6BT, Department of Crystallography and BBSRC Bloomsbury Centre for Structural Biology, Birkbeck College, Malet Street, London WC1E 7HX, UK Corresponding author e-mail:
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9
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Fogg JM, Kvaratskhelia M, White MF, Lilley DM. Distortion of DNA junctions imposed by the binding of resolving enzymes: a fluorescence study. J Mol Biol 2001; 313:751-64. [PMID: 11697901 DOI: 10.1006/jmbi.2001.5081] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Junction-resolving enzymes are nucleases that are specific for the structure of the four-way DNA junction. The binding of RuvC of Escherichia coli and Hjc of Sulfolobus solfataricus can be followed by an increase in the fluorescence anisotropy of Cy3 terminally attached to one of the helical arms of a four-way junction. By contrast, there was no change in fluorescein anisotropy with the binding of single dimers of these proteins. Fluorescence resonance energy transfer has therefore been used between fluorescein and Cy3 fluorophores attached to the ends of helical arms to analyse the global structure of the junction on protein binding. The results indicate that both enzymes induce a marked change in the global DNA conformation on the binding of a single dimer. The structure of the protein-junction complexes is independent of the presence or absence of divalent metal ions, unlike that of the protein-free junction. The structures of the RuvC and Hjc complexes are different, but both represent a significant opening of the structure compared to the stacked X-structure of the protein-free junction in the presence of magnesium ions. This protein-induced opening is likely to be important in the function of these enzymes.
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Affiliation(s)
- J M Fogg
- CRC Nucleic Acid Structure Research Group, Department of Biochemistry, MSI/WTB Complex, The University of Dundee, Dundee, DD1 5EH, UK
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10
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11
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Abstract
Junction-resolving enzymes are ubiquitous nucleases that are important for DNA repair and recombination and act on DNA molecules containing branch points, especially four-way junctions. They show a pronounced selectivity for the structure of the DNA substrate but, despite its importance, the structural selectivity is not well understood. This poses an intriguing challenge in molecular recognition on a relatively large scale.
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Affiliation(s)
- D M Lilley
- CRC Nucleic Acid Structure Research Group, Department of Biochemistry, University of Dundee, Dundee DD1 5EH, UK.
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12
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Kvaratskhelia M, Wardleworth BN, White MF. Multiple Holliday junction resolving enzyme activities in the Crenarchaeota and Euryarchaeota. FEBS Lett 2001; 491:243-6. [PMID: 11240135 DOI: 10.1016/s0014-5793(01)02200-1] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Holliday junction resolving enzymes are required by all life forms that catalyse homologous recombination, including all cellular organisms and many bacterial and eukaryotic viruses. Here we report the identification of three distinct Holliday junction resolving enzyme activities present in two highly divergent archaeal species. Both Sulfolobus and Pyrococcus share the Hjc activity, and in addition possess unique secondary activities (Hje and Hjr). We propose by analogy with the two other domains of life that the latter enzymes are viral in origin, suggesting the widespread existence of archaeal viruses that rely on homologous recombination as part of their life cycle.
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Affiliation(s)
- M Kvaratskhelia
- Centre for Biomolecular Science, St Andrews University, Fife KY16 9ST, North Haugh, UK
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13
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Organization, Replication, Transposition, and Repair of DNA. Biochemistry 2001. [DOI: 10.1016/b978-012492543-4/50030-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Wardleworth BN, Kvaratskhelia M, White MF. Site-directed mutagenesis of the yeast resolving enzyme Cce1 reveals catalytic residues and relationship with the intron-splicing factor Mrs1. J Biol Chem 2000; 275:23725-8. [PMID: 10825168 DOI: 10.1074/jbc.m002612200] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The Holliday junction-resolving enzyme Cce1 is a magnesium-dependent endonuclease, responsible for the resolution of recombining mitochondrial DNA molecules in Saccharomyces cerevisiae. We have identified a homologue of Cce1 from Candida albicans and used a multiple sequence alignment to predict residues important for junction binding and catalysis. Twelve site-directed mutants have been constructed, expressed, purified, and characterized. Using this approach, we have identified basic residues with putative roles in both DNA recognition and catalysis of strand scission and acidic residues that have a purely catalytic role. We have shown directly by isothermal titration calorimetry that a group of acidic residues vital for catalytic activity in Cce1 act as ligands for the catalytic magnesium ions. Sequence similarities between the Cce1 proteins and the group I intron splicing factor Mrs1 suggest the latter may also possess a binding site for magnesium, with a putative role in stabilization of RNA tertiary structure or catalysis of the splicing reaction.
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Affiliation(s)
- B N Wardleworth
- Department of Biochemistry, University of Dundee, Dundee DD1 5EH, United Kingdom
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15
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Jonklaas M, Kane RR. The synthesis of 3′- and 5′-iminodiacetic acid derivatives of thymidine and their incorporation into synthetic oligonucleotides. Tetrahedron Lett 2000. [DOI: 10.1016/s0040-4039(00)00583-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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16
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Abstract
Holliday junction resolving enzymes bind specifically to four-way DNA junctions created by the process of homologous recombination, cleaving them to yield recombinant duplex DNA products. Homologous recombination is known to occur in the third domain of life, the archaea, and may constitute a simplified model for the corresponding eucaryal pathway, but has not been well characterised. Identification of a gene encoding an archaeal Holliday junction resolving enzyme, Hjc, has recently been reported in the euryarchaea, and an activity has been observed in the hyperthermophilic crenarchaeote Sulfolobus solfataricus. Here we report the identification, heterologous expression and characterisation of the Hjc protein from Sulfolobus. We demonstrate that Sulfolobus has two distinct junction resolving enzymes, Hjc and Hje, with differing substrate specificities.
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Affiliation(s)
- M Kvaratskhelia
- Department of Biochemistry, University of Dundee, Dundee, DD1 5EH, UK
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