FIG. 9.

P22L is a stabilizing mutation, and S443P is a destabilizing mutation. (A to C) Wild-type (A), P22L mutant (B), or S443P mutant (C) soluble forms of PIV5 F (F-GCNt) were expressed and purified using baculovirus. Trimers were visualized by EM, and those with prefusion (arrowheads) or postfusion (arrows) morphology are noted. The shapes of individual trimers are depicted in black to the right of the images. (D) BHK cells were transfected with plasmids encoding the F-Yn P22L mutant and wt HN, Yn-HN, or Yc-HN. Cells were imaged 24 h posttransfection.