title: Conversion of DNA gyrase into a conventional type II topoisomerase.
abstract: DNA gyrase is unique among topoisomerases in its ability to introduce negative supercoils into closed-circular DNA. We have demonstrated that deletion of the C-terminal DNA-binding domain of the A subunit of gyrase gives rise to an enzyme that cannot supercoil DNA but relaxes DNA in an ATP-dependent manner. Novobiocin, a competitive inhibitor of ATP binding by gyrase, inhibits this reaction. The truncated enzyme, unlike gyrase, does not introduce a right-handed wrap when bound to DNA and stabilizes DNA crossovers; characteristics reminiscent of conventional type II topoisomerases. This new enzyme form can decatenate DNA circles with increased efficiency compared with intact gyrase and, as a result, can complement the temperature-sensitive phenotype of a parCts mutant. Thus these results suggest that the unique properties of DNA gyrase are attributable to the wrapping of DNA around the C-terminal DNA-binding domains of the A subunits and provide an insight into the mechanism of type II topoisomerases.
authors.affiliation: Department of Biochemistry, University of Leicester, United Kingdom.
authors.forename: S C
authors.initials: SC
authors.lastname: Kampranis
authors.forename: A
authors.initials: A
authors.lastname: Maxwell
mesh_terms: D000818:Animals; D004247:DNA / Q000235:genetics / Q000378:metabolism*; D004250:DNA Topoisomerases, Type II / Q000235:genetics / Q000378:metabolism*; D004789:Enzyme Activation / Q000235:genetics; D009690:Nucleic Acid Conformation; D011487:Protein Conformation
chemical_list: D004247:DNA; D004250:DNA Topoisomerases, Type II