title: Isolation of a mitochondrial DNA topoisomerase from human leukemia cells.
abstract: Mitochondria from human acute lymphoblastic leukemia cells contain an ATP-independent DNA topoisomerase which can relax negative and positive supercoils. This enzyme has been purified 200-fold by carboxymethyl-cellulose or double stranded DNA-cellulose chromatography. In contrast to the molecular weights reported for mitochondrial topoisomerases in other systems, the native leukemia enzyme has a molecular weight of 132,000 daltons as determined by gel permeation chromatography in buffer containing 0.4 M KC1. It also exhibits a sedimentation coefficient of 7.1 S when centrifuged through a 10-30% glycerol gradient in this high salt buffer. The enzyme is presumably a type I topoisomerase analogous to those found in rat liver and Xenopus laevis mitochondria.
mesh_terms: D002845:Chromatography / Q000379:methods; D004264:DNA Topoisomerases, Type I / Q000302:isolation & purification*; D004272:DNA, Mitochondrial / Q000378:metabolism; D004273:DNA, Neoplasm / Q000378:metabolism*; D004278:DNA, Superhelical / Q000378:metabolism; D006801:Humans; D007945:Leukemia, Lymphoid / Q000201:enzymology*; D008928:Mitochondria / Q000201:enzymology*; D008970:Molecular Weight; D011489:Protein Denaturation
chemical_list: D004272:DNA, Mitochondrial; D004273:DNA, Neoplasm; D004278:DNA, Superhelical; D004264:DNA Topoisomerases, Type I