title: Three-dimensional structure of the 67K N-terminal fragment of E. coli DNA topoisomerase I.
abstract: The three-dimensional structure of the 67K amino-terminal fragment of Escherichia coli DNA topoisomerase I has been determined to 2.2 A resolution. The polypeptide folds in an unusual way to give four distinct domains enclosing a hole large enough to accommodate a double-stranded DNA. The active-site tyrosyl residue, which is involved in the transient breakage of a DNA strand and the formation of a covalent enzyme-DNA intermediate, is present at the interface of two domains. The structure suggests a plausible mechanism by which E. coli DNA topoisomerase I and other members of the same DNA topoisomerase subfamily could catalyse the passage of one DNA strand through a transient break in another strand.
authors.affiliation: Department of Biochemistry, Molecular Biology and Cell Biology, Northwestern University, Evanston, Illinois 60208.
authors.forename: C D
authors.initials: CD
authors.lastname: Lima
authors.forename: J C
authors.initials: JC
authors.lastname: Wang
authors.forename: A
authors.initials: A
authors.lastname: Mondragón
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D018360:Crystallography, X-Ray; D004264:DNA Topoisomerases, Type I / Q000737:chemistry* / Q000378:metabolism; D004926:Escherichia coli / Q000201:enzymology*; D006860:Hydrogen Bonding; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011487:Protein Conformation
chemical_list: D004264:DNA Topoisomerases, Type I