title: Micrococcus luteus DNA gyrase: active components and a model for its supercoiling of DNA.
abstract: Two active components alpha and beta of micrococcus luteus DNA gyrase, of peptide weights of 115,000 and 97,000, respectively, have been purified. Each individual component exhibits little DNA gyrase activity; the ATP-dependent negative supercoiling of a covalently closed circular DNA duplex is catalyzed by a combination of the two. Covalent closure by Escherichia coli ligase of a circular DNA containing single-chain scissions, when carried out in the presence of a combination of the DNA gyrase components alpha and beta, gives a positively supercoiled DNA upon removal of the bound protein molecules. ATP was not present during the ligase treatment; therefore the positive supercoiling of DNA observed is a result of the binding of gyrase molecules, presumably as multi-subunit oligomers, during the ligation step. This is in contrast to the negative supercoiling of DNA catalyzed by gyrase in the presence of ATP. A model in which negative supercoiling of DNA is achieved by ATP-modulated repetitive wrapping of the DNA around gyrase is described. The model also suggests a plausible mode of action by which translocation of a DNA along its helix axis can be actively driven by an ATPase.
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D004269:DNA, Bacterial / Q000378:metabolism; D004278:DNA, Superhelical / Q000378:metabolism; D046911:Macromolecular Substances / Q000037:antagonists & inhibitors; D008274:Magnesium / Q000378:metabolism; D008837:Micrococcus / Q000201:enzymology; D008956:Models, Chemical; D008970:Molecular Weight; D009690:Nucleic Acid Conformation; D011188:Potassium / Q000378:metabolism; D013095:Spermidine / Q000494:pharmacology
chemical_list: D000900:Anti-Bacterial Agents; D004269:DNA, Bacterial; D004278:DNA, Superhelical; D046911:Macromolecular Substances; D000255:Adenosine Triphosphate; D008274:Magnesium; D011188:Potassium; D013095:Spermidine