Figure 3.

SARS-CoV-2 exonuclease activity with uridine- or uridine-analogue terminated RNA. A mixture of 500 nM template-loop-primer terminated at its 3′ end with either U (a), 2′-NH₂-U (d), Zidovudine (AZT) (g) or Stavudine (Sta) (j) (sequences shown in b,e,h,k) and SARS-CoV-2 pre-assembled exonuclease complex (Nsp14/Nsp10) was incubated at 37 °C for 10 min. These intact RNAs (b,e,h,k) and their respective exonuclease reaction products (c,f,i,l) were analyzed by MALDI-TOF MS. The signal intensity was normalized to the highest peak.