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. Author manuscript; available in PMC: 2011 Apr 6.
Published in final edited form as: Biochemistry. 2010 Apr 6;49(13):2786–2795. doi: 10.1021/bi902204v

Figure 1.

Figure 1

Reversible DNA cleavage and ligation by topoisomerase IB and DNA strand exchange. The native strand (black) is cleaved during the first transesterification reaction, and can dissociate from the Topo-DNA covalent complex. Another DNA strand with a 5′-OH (red) can associate and attack the DNA-protein phosphotyrosyl bond, resulting in DNA rearrangements. The extent of binding and ligation of strands to the covalent complex is determined by the binding equilibrium (KD) and the reversible ligation equilibrium (klig/kcl = KL).