title: DNA cleavage is not required for the binding of quinolone drugs to the DNA gyrase-DNA complex.
abstract: The primary target for the quinolone group of antibacterial agents is DNA gyrase. One model for the interaction of quinolone drugs with gyrase and DNA suggests that the drugs bind to the single-stranded regions revealed following DNA cleavage by the enzyme. We have tested this hypothesis by using mutants which have the active-site tyrosine in the gyrase A subunit altered to phenylalanine or serine. We have found that proteins bearing these mutations are still able to bind drug, suggesting that DNA cleavage is not a prerequisite for drug binding. We have also found that the blocking of transcription by RNA polymerase in vitro by the gyrase-quinolone complex on DNA does not occur when the active-site tyrosine is mutated to serine; i.e., polymerase blocking requires DNA cleavage.
authors.affiliation: Department of Biochemistry, University of Leicester, UK.
authors.forename: S E
authors.initials: SE
authors.lastname: Critchlow
authors.forename: A
authors.initials: A
authors.lastname: Maxwell
mesh_terms: D000890:Anti-Infective Agents / Q000378:metabolism*; D001483:Base Sequence; D001665:Binding Sites; D002118:Calcium / Q000494:pharmacology; D002939:Ciprofloxacin / Q000378:metabolism*; D003001:Cloning, Molecular; D004247:DNA / Q000378:metabolism*; D017931:DNA Primers; D004250:DNA Topoisomerases, Type II / Q000737:chemistry / Q000378:metabolism*; D004278:DNA, Superhelical / Q000378:metabolism; D007700:Kinetics; D046911:Macromolecular Substances; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D017354:Point Mutation; D016133:Polymerase Chain Reaction; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D015183:Restriction Mapping; D014158:Transcription, Genetic; D014443:Tyrosine
chemical_list: D000890:Anti-Infective Agents; D017931:DNA Primers; D004278:DNA, Superhelical; D046911:Macromolecular Substances; D011994:Recombinant Proteins; D014443:Tyrosine; D002939:Ciprofloxacin; D004247:DNA; D004250:DNA Topoisomerases, Type II; D002118:Calcium