Figure 5.

(A) Global tertiary and secondary structure of the RT initiation complex (RTIC) at the +1 extension state. The cryo-EM density encompasses all of vRNA H1, the PBS, and the tRNA. Density of H2 is weak near the apical end. (B) Three different global cryo-EM class averages of the RTIC. Alternative RNA models were generated by treating the H1, H2, and extended tRNA helices as rigid bodies. The flexible junctions are indicated in A. The center class showed very little density for the upper stem of H2. (Data adapted from Larsen et al. 2018.)