The activity and selectivity of fission yeast Pop2p are affected by a high affinity for Zn²⁺ and Mn²⁺ in the active site

Dynamic modulation of Pop2p deadenylase activity. (A) Titration experiments in which Pop2p equilibrated in physiological concentrations of Mg²⁺ and Mn²⁺ is gradually inactivated by addition of increasing amounts of Zn²⁺ as indicated. Only the region of the gels corresponding to RNA fragments sized between 20 and 30 nt is shown for clarity. (B) Reactivation of the Zn²⁺-bound form of Pop2p by gradual increase of the concentration of Mg²⁺ in the presence of Mn²⁺ and Zn²⁺ as indicated. The active site D50A mutant of Pop2p is shown as a negative control for both experiments.