Fig. 6

CR9501-bound F resembles a naturally occurring prefusion state. a C3 symmetry was applied to the monomeric prefusion F-CR9501 structure to generate a prefusion F trimer. The resulting trimer is shown as ribbons and transparent molecular surfaces, with the three protomers colored blue, gray, and white, viewed looking toward the viral membrane. Predicted clashes between protomers are indicated with red. b Two states of prefusion F identified in 26 previously determined structures are shown and colored as in (a). c The two states of prefusion F are shown in pink and blue ribbons and viewed looking toward (left) or along (right) the viral membrane. The top insets show the views denoted by the arrows at (1) the trimer apex viewed from the central cavity, (2) the heptad repeat B and (3) the F₂ subunit. The bottom insets are the same but include the monomer from the CR9501-bound structure shown in green