title: Role of the divalent cation in topoisomerase II mediated reactions.
abstract: The effects of magnesium ions on interactions between Drosophila melanogaster topoisomerase II and its substrates were assessed by a number of kinetic and binding assays. Results indicated that the divalent cation plays two distinct functions in promoting enzyme-substrate interactions. One class of magnesium ions participates directly in enzyme-mediated DNA cleavage reactions. A second class of magnesium ions participates directly in topoisomerase II mediated ATPase reactions and functions by providing the enzyme with a magnesium-ATP substrate. In contrast, the divalent cation did not affect the quaternary structure of the enzyme, was not required for the site-specific binding of topoisomerase II to DNA, and did not affect the enzyme's ability to discern the topological state of its nucleic acid substrate.
authors.affiliation: Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, Tennessee 37232.
authors.forename: N
authors.initials: N
authors.lastname: Osheroff
mesh_terms: D000818:Animals; D002413:Cations, Divalent; D002467:Cell Nucleus / Q000201:enzymology; D002478:Cells, Cultured; D004250:DNA Topoisomerases, Type II / Q000378:metabolism*; D004331:Drosophila melanogaster / Q000201:enzymology; D007700:Kinetics; D008274:Magnesium / Q000494:pharmacology
chemical_list: D002413:Cations, Divalent; D004250:DNA Topoisomerases, Type II; D008274:Magnesium