Figure S1.

Purification and Assembly of nsp13 and the RTC, Related to Figure 1

A. (left) SDS-PAGE of purified SARS-CoV-2 nsp7/8, nsp12, and nsp13.

(right) Size exclusion chromatography profiles for the purified nsp7/8, nsp12, and nsp13. Nsp7/8 are known to form high molecular weight complexes (Xiao et al., 2012; Zhai et al., 2005), which we observed in equilibrium with the 31 kDa nsp7/nsp8 heterodimer. For assembly of the holo-RdRp, we isolated the peak corresponding to the 31 kDa heterodimer.

B. Purification of RTC by size exclusion chromatography.

(left) Chromatogram of RTC (blue trace) and individual components (gray trace) labeled.

C. Holo-RdRp elongates the primer-strand of the RNA scaffold shown in the presence of NTPs. Original primer (20-mer, dark red), 27-mer AU elongated product (red), 32-mer AUC product (pink), 40-mer AUCG product (orange) and the product of nsp8-mediated TATAse activity (yellow; Tvarogová et al., 2019). Products, taken at a 30-minute time point, are shown for a representative gel (n = 2) and are visualized alongside Decade RNA ladder (Invitrogen).