FIGURE 4.

Metal selectivity of human recombinant TDP2. A, representative denaturing PAGE gels show the processing of the ssY19 with the presence of 5 mm Mg²⁺, Co²⁺, Mn²⁺, Ca²⁺, Zn²⁺, or without metal ions. B, dosimetric quantification of 5′-end processing for the different substrates is shown. C, TDP2 processing activity in the presence of mixed metals is shown. 5′-Tyrosyl-DNA phosphodiesterase activity of TDP2 was assayed in the presence of varying concentrations of Mg²⁺ in the absence or presence of Ca²⁺. The reactions were carried out using 7.9 nm TDP2 and stopped at 2 min. In the mixed metal reactions, the total amount of metals was 1 mm.