(a) Top view of RSV F apo (PDB ID 4MMS, green) superposed with the JNJ-2408068-bound (light purple) and D489Y (tan) RSV F crystal structures. The electron density of JNJ-2408068 in the bound structure is shown as a black mesh. The three RSV F protomers (labeled A, Band C) are separated by dashed gray lines emanating from the center of the three-fold axis. Salt bridges and interprotomeric hydrogen bonds between Lys394, Thr400 and Asp489 are shown as dotted lines in the lower left for the bound structure and to the right for the apo structure, and are absent in the D489Y structure at the top left. (b) Side view of the D489Y and JNJ-2408068-bound RSV F structures, colored as in a. Hydrogen bonds and salt bridges in the bound structure are shown as dotted lines. Hydrophobic side chains in the fusion peptide (Leu138, Phe140 and Leu141) and in the HRB (Tyr489) are shown with transparent molecular surfaces.