Fig. 3.

(A) Schematic illustrating the structural domains of the holo-RdRp subunits nsp7, 8 and 12. (B) View of the apo holo-RdRp showing the “cupped right hand” structure of nsp12 (left). A 90° rotation reveals the NiRAN domain and nsp7/8 heterodimer interface with nsp12 (right). (C) The nsp8 N-terminal helices are ordered in the presence of an upstream RNA duplex substrate. Figures in panels A–C were generated using PDB 6XEZ[7]. The original apo holo-RdRp structure was from SARS-CoV-1 (6NUR) [45]. Published RNA bound Holo-RdRp structures include 6YYT [42] and 7BV2 [54].