Figure 1.

Biochemical determinants of SARS-CoV-2 nsp12 activity. (A) Purified recombinant nsp12, nsp7 and nsp8. (B) Schematic showing the structure of the double-stranded RNA substrate that served as a template for primer extension. (C) Enzyme activity is highest at 10 mM-50 mM KCl. Subsequent steady-state reactions were carried out with 50 mM KCl. (D and E) The effect of pH or Mg²⁺/Mn²⁺ concentration on nsp12 activity. All reactions are carried out with 5 mM Mn²⁺ at pH 7.5. (F) Single rUTP incorporation with double-stranded RNA template. Results showed a ∼7.5-fold higher activity with Mn²⁺ than Mg²⁺. Error bars in C, D, E and F represent standard deviation of the mean (n = 3)