Figure 4.

Schematic model of how hydrolysis of one ATP could drive DNA transport by topoisomerase II. The various domains of the topoisomerase II dimer are shown in different colors, with the domains of one monomer numbered starting from the N terminus; the relative orientation of each number and its domain remains constant during the reaction. The C-terminal domain, which is neither conserved nor required for catalytic activity, is not shown. The G and T segments of DNA are shown as green and purple rods, respectively. The exit of the T segment from the topoisomerase is not shown because it is presently unclear at which step it occurs.