title: Transient DNA relaxation in Escherichia coli induced by nalidixic acid.
abstract: We report here the transient relaxation of plasmid DNA by inhibitors of DNA gyrase in Escherichia coli. Relaxation of plasmid DNA in the presence of nalidixic acid, an inhibitor of the A subunit of DNA gyrase, lasted less than 60 min. The effect of nalidixic acid was not observed in a nalA26 mutant, a strain resistant to nalidixic acid due to a mutation in the gyrA gene. Novobiocin, whose target is the B subunit of DNA gyrase, also caused transient DNA relaxation. Resupercoiling of relaxed DNA in the presence of nalidixic acid was inhibited by pretreatment of the cells with chloramphenicol. As mutations of both the rpoH and recA genes did not affect the resupercoiling reaction, this step seems to require protein synthesis that is independent of both heat shock and SOS responses.
authors.affiliation: Department of Microbiology, Faculty of Pharmaceutical Sciences, Kyushu University, Higashi-ku, Fukuoka, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Ohtsuka
authors.forename: T
authors.initials: T
authors.lastname: Mizushima
authors.forename: T
authors.initials: T
authors.lastname: Miki
authors.forename: K
authors.initials: K
authors.lastname: Sekimizu
mesh_terms: D001426:Bacterial Proteins / Q000037:antagonists & inhibitors; D002701:Chloramphenicol / Q000494:pharmacology; D004269:DNA, Bacterial / Q000187:drug effects* / Q000235:genetics; D004278:DNA, Superhelical / Q000187:drug effects* / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics* / Q000378:metabolism; D005798:Genes, Bacterial; D006360:Heat-Shock Proteins / Q000096:biosynthesis; D008565:Membrane Proteins / Q000096:biosynthesis; D009154:Mutation; D009268:Nalidixic Acid / Q000494:pharmacology*; D009675:Novobiocin / Q000494:pharmacology; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D020664:Son of Sevenless Proteins; D059005:Topoisomerase II Inhibitors
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D004278:DNA, Superhelical; D006360:Heat-Shock Proteins; D008565:Membrane Proteins; D011500:Protein Synthesis Inhibitors; D020664:Son of Sevenless Proteins; D059005:Topoisomerase II Inhibitors; D009675:Novobiocin; D009268:Nalidixic Acid; D002701:Chloramphenicol