title: Modification of norfloxacin inhibition of DNA gyrase induced by a 28 KDal DNA binding protein.
abstract: We have previously studied a clinical isolate of Providencia stuartii which showed high levels of resistance to 4-quinolones, aminoglycoside and beta-lactam antibiotics (Landini et al., 1987). DNA gyrase from this isolate was inhibited for 50% of activity at a concentration of 15 microM of norfloxacin, which is about 5-fold higher compared to the 50% inhibitory concentration for a standard DNA gyrase. It has been described that 4-quinolone inhibition of DNA gyrase is caused by their binding to DNA and by the distortion induced in DNA tertiary structure, and that affinity binding of 4-quinolones is different for DNAs in different structures. In order to detect whether the interaction between pAT 153 and a protein able to modify DNA tertiary structure could affect norfloxacin inhibitory concentrations for DNA gyrase we purified from the clinical isolate of Providencia stuartii a DNA binding protein of about 28 KDal which induces changes in supercoiling degree of DNA. Assays of DNA gyrase activity were performed on the complex pAT 153-DNA binding protein-norfloxacin. Results showed an increase from 15 microM to 20 microM of 50% norfloxacin inhibitory concentration for DNA gyrase when pAT 153 was complexed with the 28 KDal protein.
authors.affiliation: Institute of Microbiology, University of Pavia, Italy.
authors.forename: P
authors.initials: P
authors.lastname: Landini
authors.forename: L
authors.initials: L
authors.lastname: Pagani
authors.forename: M
authors.initials: M
authors.lastname: Debiaggi
authors.forename: P M
authors.initials: PM
authors.lastname: Cereda
authors.forename: E
authors.initials: E
authors.lastname: Romero
mesh_terms: D004265:DNA Helicases / Q000378:metabolism; D004269:DNA, Bacterial / Q000378:metabolism; D004278:DNA, Superhelical / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism*; D004352:Drug Resistance, Microbial; D004587:Electrophoresis, Agar Gel; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D009643:Norfloxacin / Q000378:metabolism / Q000494:pharmacology*; D011485:Protein Binding; D011511:Proteus / Q000187:drug effects*; D011532:Providencia / Q000187:drug effects* / Q000201:enzymology / Q000235:genetics; D059005:Topoisomerase II Inhibitors
chemical_list: D004269:DNA, Bacterial; D004278:DNA, Superhelical; D004268:DNA-Binding Proteins; D059005:Topoisomerase II Inhibitors; D004265:DNA Helicases; D009643:Norfloxacin