title: DNA gyrase activities from Rhodobacter capsulatus: analysis of target(s) of coumarins and cloning of the gyrB locus.
abstract: Bacterial DNA gyrase is composed of two subunits, gyrase A and B, and is responsible for negatively supercoiling DNA in an ATP-dependent manner. The coumarin antibiotics novobiocin and coumermycin are known inhibitors of bacterial DNA gyrase in vivo and in vitro. We have cloned, mapped, and partially sequenced Rhodobacter capsulatus gyrB which encodes the gyrase B subunit that is presumably involved in binding to coumarins. DNA gyrase activities from crude extracts of R. capsulatus were detected and it was shown that the R. capsulatus activity is (1) inhibited by novobiocin and coumermycin, (2) ATP-dependent and, (3) present in highly aerated and anaerobically grown cells. We previously observed that when R. capsulatus coumermycin-resistant strains are continuously recultured on media containing coumermycin they sometimes acquired mutations in hel genes (i.e., cytochromes c biogenesis mutations). We discuss the possibility that coumarins may inhibit cytochromes c biogenesis as a second target in R. capsulatus via hel (i.e., a putative ATP-dependent heme exporter).
authors.affiliation: Department of Biology, Washington University, St. Louis, MO 63130.
authors.forename: R G
authors.initials: RG
authors.lastname: Kranz
authors.forename: D L
authors.initials: DL
authors.lastname: Beckman
authors.forename: D
authors.initials: D
authors.lastname: Foster-Hartnett
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000332:Aerobiosis; D000595:Amino Acid Sequence; D049933:Aminocoumarins; D000693:Anaerobiosis; D003001:Cloning, Molecular; D003374:Coumarins / Q000494:pharmacology; D003574:Cytochrome c Group / Q000096:biosynthesis; D004250:DNA Topoisomerases, Type II / Q000235:genetics / Q000378:metabolism*; D004352:Drug Resistance, Microbial; D005798:Genes, Bacterial; D008969:Molecular Sequence Data; D009675:Novobiocin / Q000494:pharmacology*; D016354:Rhodobacter capsulatus / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics; D059005:Topoisomerase II Inhibitors
chemical_list: D049933:Aminocoumarins; D003374:Coumarins; D003574:Cytochrome c Group; D059005:Topoisomerase II Inhibitors; D009675:Novobiocin; D000255:Adenosine Triphosphate; D004250:DNA Topoisomerases, Type II; C004628:coumermycin