Fig. 3: Cryo-EM structure of the RSV polymerase in complex with the trailer complementary (TrC10) promoter of the RSV antigenome.

a, The interactions between the RdRp domain of RSV L and TrC10 RNA template. The RdRp domain is coloured the same as in Fig. 2a, and the TrC10 is coloured orange. b, Residues of the RSV L involved in the interactions with TrC10. The residues are coloured the same as in a. The RNA residues with missing density are coloured grey. Residues in rectangles interact with RNA bases. Residues in bold are conserved across NNS RNA viruses. c, The superimposition of the RSV polymerase in complex with Le10 (Le10-bound) and TrC10 (TrC10-bound). The Le10 RNA is shown in yellow, as in Fig. 2a, and the TrC10 RNA is shown in orange, as in a. The interactions of Le10 T3C and TrC10 T1U (at the −1 catalytic site) and Le10 T4G and TrC10 T2G (at the +1 catalytic site) with RSV polymerase (L–P) are shown in the right panels (I) and (II), respectively. The ‘GDN’ motif is shown as magenta spheres. The supporting helix (residues 666–676) and supporting loop (residues 656–665) are shown for Le10-bound (tan) and TrC10-bound (red) RSV polymerases. Note that part of the supporting loop is too flexible to build in both structures.