Figure 3.

Catalytic activity of the 10-23 DNA enzyme under multiple turnover conditions. (A) Initial velocities were measured over the first 10% of the reaction, using a fixed concentration of enzyme (0.004 nM) and varying concentrations of substrate (0.02–4 nM). The 17-mer RNA substrate, corresponding to the start codon region of HIV-1 gag/pol mRNA, was prepared by in vitro transcription. Reaction conditions: 2 mM MgCl₂ and 150 mM NaCl (pH 7.5) at 37°C. Data from two independent experiments are shown and were fit to the Michaelis–Menten equation: v = k_cat [E]/(K_m + [S]). (B) Catalytic rates were determined in the presence of saturating substrate (100 nM) and varying concentrations of MgCl₂ (2–300 mM). Reaction conditions were otherwise as above. Data from two independent experiments are shown and were fit to the Michaelis–Menten equation to obtain the apparent K_m for Mg²⁺.