Figure 3.

Biochemical determinants of SARS-CoV nsp12 activity. (A and B) Tests to determine the influence of temperature indicated that nsp12 incorporates ATP most efficiently at 37°C, although this effect mainly stemmed from increased initiation. Based on these results, 30°C was taken as the standard for subsequent experiments. (C and D) Titration of the Mg²⁺ concentration showed that activity reaches its maximum at 6 mM. (E and F) The effect of pH on RdRp activity was evident as well, with lower pHs limiting the activity of the enzyme. All reactions were incubated for 60 min at 30°C, unless otherwise indicated. Error bars in A, C and E represent standard error of the mean (n = 3).