Modulation of product formation by Mg2+ in hTDP2-mediated 5'-phosphotyrosyl bond cleavage reaction. (A) hTDP2 (90 pM) was reacted with a 5-sub (40 nM) at 37°C for 7 min. The details of the reaction conditions are described in "Materials and Methods." (B) Data obtained in Panel A and a separate set of experiments using 45 pM TDP2 under similar reaction conditions as in Panel A were plotted. "Pdt" represents respective formed product in this and other figures in the paper.