Figure 4.

Zn²⁺-dependence of M1 RNA-catalyzed cleavage of all-ribose ptRNA^Gly (Hill analysis). The Zn²⁺-concentration was varied in the range of 0–80 mM: (A) at constant [Sr²⁺] (12 mM) and pH 6.0; (B) in the absence of a second metal ion at pH 6.5; (C) at constant [$\text{Co}{\left({\text{NH}}_3\right)}_6^{3+}$] (20 mM) and pH 6.0. Data were analyzed by non-linear regression analysis using the Hill equation v = V_max·[Zn²⁺]ⁿ/(K′_Zn + [Zn²⁺]ⁿ) as described previously (8). The Hill coefficient (n_H) was determined as 2.2 ± 0.03 in (A), 2.8 ± 0.02 in (B) and 1.80 ± 0.04 in (C). For further details, see Materials and Methods.