Figure 9.

Low-resolution SAXS structure of the trimeric complex is consistent with a 1:1:1 stoichiometry. The SAXS envelope is shown in three different orientations with the calculated density filled in with existing protein structures and modeled nucleic acid. In purple is a monomer of nsp1β from PRRSV strain XH-GD (PDB entry 3MTV (22)) with the theorized RBM helix depicted in red. In gold and fuchsia are the KH1 and KH2 domains of PCBP2, respectively (PDB entry 2JZX (24)). In green is shown a short, C-rich RNA motif that was co-crystalized with KH1 alone (PDB entry 2PY9 (23)), which is shown as a frame of reference for how our idealized RNA probe (orange) may fit. In teal is the KH3 domain of PCBP2 (PDB entry 2P2R (25)). The RNA molecule is shown in orange with the C-rich motif shown in blue. All fitting was carried out manually using PyMOL (27).