title: Nucleotide binding to the 43-kilodalton N-terminal fragment of the DNA gyrase B protein.
abstract: The binding of ADPNP (5'-adenylyl beta,gamma-imidodiphosphate) to the 43-kDa N-terminal fragment of the DNA gyrase B protein is found to stabilize a dimer of the protein. Analysis of the kinetics of binding of ADPNP to the fragment suggests that protein dimers can contain 1 or 2 molecules of bound nucleotide. ATP, ADP, or coumarin drugs inhibit the binding of ADPNP. The rate of dissociation of ADPNP from the 43-kDa protein is found to be very slow and unaffected by the presence of other nucleotides. These data can be accommodated by a scheme in which the 43-kDa monomer forms a short-lived complex with ADPNP that can be converted into long-lived dimer complexes containing either 1 or 2 molecules of bound ADPNP; dimer formation with 2 bound ADPNPs is strongly favored. Coumarin drugs inhibit the binding of ADPNP to the 43-kDa fragment, with novobiocin binding to the protein with a stoichiometry of 1:1 and coumermycin binding with a stoichiometry of 0.5:1.
authors.affiliation: Department of Biochemistry, University of Leicester, U.K.
authors.forename: J A
authors.initials: JA
authors.lastname: Ali
authors.forename: G
authors.initials: G
authors.lastname: Orphanides
authors.forename: A
authors.initials: A
authors.lastname: Maxwell
mesh_terms: D000244:Adenosine Diphosphate / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000494:pharmacology; D000266:Adenylyl Imidodiphosphate / Q000378:metabolism*; D003374:Coumarins / Q000494:pharmacology; D003432:Cross-Linking Reagents; D027081:DNA Gyrase; D004250:DNA Topoisomerases, Type II / Q000737:chemistry / Q000378:metabolism*; D004120:Dimethyl Suberimidate / Q000494:pharmacology; D004926:Escherichia coli / Q000201:enzymology; D007700:Kinetics; D046911:Macromolecular Substances; D009675:Novobiocin / Q000378:metabolism; D010446:Peptide Fragments / Q000737:chemistry / Q000378:metabolism*; D014357:Trypsin / Q000378:metabolism
chemical_list: D003374:Coumarins; D003432:Cross-Linking Reagents; D046911:Macromolecular Substances; D010446:Peptide Fragments; D009675:Novobiocin; D000266:Adenylyl Imidodiphosphate; D004120:Dimethyl Suberimidate; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; C030123:coumarin; D014357:Trypsin; D027081:DNA Gyrase; D004250:DNA Topoisomerases, Type II