title: The capture of a DNA double helix by an ATP-dependent protein clamp: a key step in DNA transport by type II DNA topoisomerases.
abstract: The binding of linear and circular forms of DNA to yeast DNA topoisomerase II or its complex with AMPPNP, the nonhydrolyzable beta,gamma-imido analog of ATP, was carried out to probe the ATP analog-induced conformational change of the enzyme. Binding of the ATP analog is shown to convert the enzyme to a circular clamp with an annulet, through which only a linear DNA can pass; subsequent circularization of the bound linear DNA forms a salt-stable catenane between the protein circular clamp and the DNA ring. Analysis of catenane formation between a small DNA ring originally bound to the topoisomerase and a large DNA ring subsequently added, under conditions such that the two do not exchange, supports a model in which a second DNA double-helix can enter the open jaws of a DNA-bound protein clamp, and the closure of the jaws upon ATP-binding traps the second duplex and transports it through an enzyme-operated gate in the first DNA duplex.
authors.affiliation: Department of Biochemistry and Molecular Biology, Harvard University, Cambridge, Massachusetts 02138.
authors.forename: J
authors.initials: J
authors.lastname: Roca
authors.forename: J C
authors.initials: JC
authors.lastname: Wang
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism*; D000266:Adenylyl Imidodiphosphate / Q000378:metabolism; D004247:DNA / Q000378:metabolism*; D004250:DNA Topoisomerases, Type II / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000378:metabolism*; D009038:Motion; D011487:Protein Conformation; D012441:Saccharomyces cerevisiae / Q000201:enzymology
chemical_list: D004268:DNA-Binding Proteins; D000266:Adenylyl Imidodiphosphate; D004247:DNA; D000251:Adenosine Triphosphatases; D004250:DNA Topoisomerases, Type II