Figure 4.

Rate constants for the cleavage of S11O, S11SpS and S11RpS by the R32 ribozyme ([metal chloride] = 25 mM; 50 mM Tris–HCl, pH 6, 37°C). Metal salts were as follows: CdCl₂, red; MgCl₂, blue; and MnCl₂, green. The rate constants for reactions in the presence of single metal ions are shown in (A) and the effects of mixing two metal ions on the rate constants as shown for: MgCl₂ + CdCl₂, MnCl₂ + CdCl₂ and MnCl₂ + MgCl₂ in (B), (C) and (D), respectively. The open circles show the results of mixing two metal ions (1:1; total concentration, 25 mM).