title: Gyrase mutants affect mutation in a localized region of Haemophilus influenzae.
abstract: Spontaneous mutation was greatly increased in a localized region of the chromosome of Haemophilus influenzae, but not at other loci, by a nov gene mutation called novC that increased DNA supercoiling. Another nov gene mutation, called novD, decreased spontaneous mutation in the same localized region and depressed DNA supercoiling. Both mutations, which code for the gyrase B subunit, have been cloned, and the cloned versions also altered mutagenesis and supercoiling in a similar fashion as the two mutations on the chromosome, although novC on the plasmid caused somewhat less mutation than on the chromosome. We postulate that the effects of the gyrase B mutations on the chromosome result from their effects on supercoiling because of increased gyrase near its site of production. The fact that the novC on a plasmid does not cause mutagenesis except in the same localized region that is altered by this mutation on the chromosome, is difficult to explain. One possibility is that there is a complex of proteins in this region which is necessary for the effects on supercoiling and thus, also on mutagenesis.
authors.affiliation: Biology Department, Brookhaven National Laboratory, Upton, NY 11973, USA.
authors.forename: J K
authors.initials: JK
authors.lastname: Setlow
authors.forename: D
authors.initials: D
authors.lastname: Haines
authors.forename: E
authors.initials: E
authors.lastname: Cabrera-Juárez
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001426:Bacterial Proteins / Q000235:genetics; D002876:Chromosomes, Bacterial / Q000235:genetics; D004250:DNA Topoisomerases, Type II / Q000235:genetics*; D004269:DNA, Bacterial / Q000235:genetics*; D004268:DNA-Binding Proteins; D004352:Drug Resistance, Microbial / Q000235:genetics; D005787:Gene Frequency; D023061:Gene Order; D008040:Genetic Linkage; D006193:Haemophilus influenzae / Q000187:drug effects / Q000235:genetics* / Q000254:growth & development; D008826:Microbial Sensitivity Tests; D009154:Mutation; D009675:Novobiocin / Q000494:pharmacology
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D004269:DNA, Bacterial; D004268:DNA-Binding Proteins; C084168:rec-1 protein, Haemophilus influenzae; D009675:Novobiocin; D004250:DNA Topoisomerases, Type II