title: Regulation of DNA supercoiling in Escherichia coli: genetic basis of a compensatory mutation in DNA gyrase.
abstract: Bacterial DNA supercoiling is controlled by balancing the supercoiling activity of DNA gyrase and the relaxing activity of DNA topoisomerase I. We have characterized the gyrB gene from a top A deletion mutant of Escherichia coli (DM800) that has a compensatory mutation in gyrB, lowering the activity of gyrase 10-fold, and thereby redressing the intracellular level of supercoiling. The mutant gene differs from the wild type in carrying three rather than two direct tandem repeats of a 6 bp sequence encoding Ala-Arg. We suggest this novel mutation affects domain spacing and was generated by an unequal crossing over event, possibly involving gyrase.
authors.affiliation: Department of Cellular and Molecular Sciences, St George's Hospital Medical School, University of London, England.
authors.forename: F
authors.initials: F
authors.lastname: McEachern
authors.forename: L M
authors.initials: LM
authors.lastname: Fisher
mesh_terms: D001483:Base Sequence; D004250:DNA Topoisomerases, Type II / Q000235:genetics*; D004278:DNA, Superhelical / Q000235:genetics*; D004926:Escherichia coli / Q000235:genetics* / Q000648:ultrastructure; D005798:Genes, Bacterial; D009154:Mutation; D015183:Restriction Mapping; D013329:Structure-Activity Relationship
chemical_list: D004278:DNA, Superhelical; D004250:DNA Topoisomerases, Type II