title: DNA gyrase: an enzyme that introduces superhelical turns into DNA.
abstract: Relaxed closed-circular DNA is converted to negatively supercoiled DNA by DNA gyrase. This enzyme has been purified from Escherichia coli cells. The reaction requires ATP and Mg++ and is stimulated by spermidine. The enzyme acts equally well on relaxed closed-circular colicin E1, phage lambda, and simian virus 40 DNA. The final superhelix density of the DNA can be considerably greater than that found in intracellularly supercoiled DNA.
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D003090:Coliphages; D004269:DNA, Bacterial / Q000378:metabolism; D004270:DNA, Circular / Q000378:metabolism*; D004279:DNA, Viral / Q000378:metabolism; D004789:Enzyme Activation; D004926:Escherichia coli / Q000201:enzymology*; D007700:Kinetics; D008274:Magnesium / Q000494:pharmacology; D009690:Nucleic Acid Conformation; D010957:Plasmids; D013539:Simian virus 40; D013095:Spermidine / Q000494:pharmacology
chemical_list: D004269:DNA, Bacterial; D004270:DNA, Circular; D004279:DNA, Viral; D000255:Adenosine Triphosphate; D008274:Magnesium; D013095:Spermidine