title: The complex between a four-way DNA junction and T7 endonuclease I.
abstract: The junction-resolving enzyme endonuclease I is selective for the structure of the DNA four-way (Holliday) junction. The enzyme binds to a four-way junction in two possible orientations, with a 4:1 ratio, opening the DNA structure at the centre and changing the global structure into a 90 degrees cross of approximately coaxial helices. The nuclease cleaves the continuous strands of the junction in each orientation. Binding leads to pronounced regions of protection of the DNA against hydroxyl radical attack. Using all this information together with the known structure of the enzyme and the structure of the BglI-DNA complex, we have constructed a model of the complex of endonuclease I and a DNA junction. This shows how the enzyme is selective for the structure of a four-way junction, such that both continuous strands can be accommodated into the two active sites so that a productive resolution event is possible.
authors.affiliation: Cancer Research UK Nucleic Acid Structure Research Group, Department of Biochemistry, MSI/WTB Complex, The University of Dundee, Dundee DD1 5EH, UK.
authors.forename: Anne-Cécile
authors.initials: AC
authors.lastname: Déclais
authors.forename: Jonathan M
authors.initials: JM
authors.lastname: Fogg
authors.forename: Alasdair D J
authors.initials: AD
authors.lastname: Freeman
authors.forename: Franck
authors.initials: F
authors.lastname: Coste
authors.forename: Jonathan M
authors.initials: JM
authors.lastname: Hadden
authors.forename: Simon E V
authors.initials: SE
authors.lastname: Phillips
authors.forename: David M J
authors.initials: DM
authors.lastname: Lilley
mesh_terms: D015075:2-Aminopurine / Q000378:metabolism; D017123:Bacteriophage T7 / Q000201:enzymology*; D001665:Binding Sites; D002118:Calcium / Q000378:metabolism; D002413:Cations, Divalent / Q000378:metabolism; D004260:DNA Repair; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D003850:Deoxyribonuclease I / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D017665:Hydroxyl Radical / Q000378:metabolism; D007700:Kinetics; D008274:Magnesium / Q000378:metabolism; D017895:Manganese Compounds / Q000378:metabolism; D008958:Models, Molecular; D009690:Nucleic Acid Conformation; D010087:Oxides / Q000378:metabolism; D010761:Phosphorus Radioisotopes; D011485:Protein Binding; D011995:Recombination, Genetic; D013941:Thymine / Q000378:metabolism
chemical_list: D002413:Cations, Divalent; D004269:DNA, Bacterial; D017895:Manganese Compounds; D010087:Oxides; D010761:Phosphorus Radioisotopes; C048856:permanganic acid; D017665:Hydroxyl Radical; D015075:2-Aminopurine; D003850:Deoxyribonuclease I; D008274:Magnesium; D013941:Thymine; D002118:Calcium