Triphosphorylation kinetics of TPR1e.

<p><b>(A)</b> At a Tmp concentration of 1 mM, the triphosphorylation kinetics are shown for synthetic seawater at 22°C (black triangles, k_obs = 0.0014 min^-1, max = 93%), and at 40°C (empty squares, k_obs = 0.0039 min^-1, max = 97%). For comparison, the reaction kinetics are shown for 54 mM MgCl₂ in Tris/HCl pH 8.3 at 22°C (black circles, k_obs = 0.020 min^-1, max = 93%). This latter condition lacks all seawater components with exception of Mg²⁺. Error bars are standard deviations from triplicate experiments, and are smaller than the symbols if not visible. Curves are single-exponential fits to the data. <b>(B)</b> Titration of the Tmp concentration in the reaction at 22°C, in synthetic seawater (black triangles) and in 54 mM MgCl₂ with 50 mM Tris/HCl pH 8.3 (black circles). The offset between the linear fits (grey lines) is 15-fold, on average. <b>(C)</b> Titration of sodium chloride into a triphosphorylation ribozyme reaction containing 50 mM Tmp and 140 mM MgCl₂. The grey line is a single-exponential fit to the data (with offset) and identifies a 1.9-fold reduction in k_obs at 470 mM [NaCl], the same NaCl concentration as in synthetic seawater (dashed line). Error bars are standard deviations from triplicate experiments, and are smaller than the symbols if not visible.