title: Crystal structure of the Holliday junction resolving enzyme T7 endonuclease I.
abstract: We have solved the crystal structure of the Holliday junction resolving enzyme T7 endonuclease I at 2.1 A resolution using the multiwavelength anomalous dispersion (MAD) technique. Endonuclease I exhibits strong structural specificity for four-way DNA junctions. The structure shows that it forms a symmetric homodimer arranged in two well-separated domains. Each domain, however, is composed of elements from both subunits, and amino acid side chains from both protomers contribute to the active site. While no significant structural similarity could be detected with any other junction resolving enzyme, the active site is similar to that found in several restriction endonucleases. T7 endonuclease I therefore represents the first crystal structure of a junction resolving enzyme that is a member of the nuclease superfamily of enzymes.
authors.affiliation: Astbury Centre for Structural Molecular Biology, School of Biochemistry and Molecular Biology, University of Leeds, Leeds LS2 9JT, UK.
authors.forename: J M
authors.initials: JM
authors.lastname: Hadden
authors.forename: M A
authors.initials: MA
authors.lastname: Convery
authors.forename: A C
authors.initials: AC
authors.lastname: Déclais
authors.forename: D M
authors.initials: DM
authors.lastname: Lilley
authors.forename: S E
authors.initials: SE
authors.lastname: Phillips
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry; D017123:Bacteriophage T7 / Q000201:enzymology*; D001665:Binding Sites; D017124:Conserved Sequence; D018360:Crystallography, X-Ray; D004247:DNA / Q000235:genetics / Q000378:metabolism; D004262:DNA Restriction Enzymes / Q000737:chemistry; D003850:Deoxyribonuclease I / Q000737:chemistry* / Q000378:metabolism*; D019281:Dimerization; D004706:Endodeoxyribonucleases / Q000737:chemistry / Q000235:genetics; D029968:Escherichia coli Proteins; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation; D017433:Protein Structure, Secondary; D011995:Recombination, Genetic; D013379:Substrate Specificity
chemical_list: D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; C069806:ruvC protein, E coli; D004247:DNA; D004706:Endodeoxyribonucleases; D004262:DNA Restriction Enzymes; D003850:Deoxyribonuclease I; C035571:endodeoxyribonuclease VII