Role of the divalent cation in topoisomerase II mediated reactions.
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.[1]References
- Role of the divalent cation in topoisomerase II mediated reactions. Osheroff, N. Biochemistry (1987) [Pubmed]
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