FIG. 6.

Analysis of budding of rSV5 harboring F cytoplasmic tail truncations. 293T cells were infected with wt rSV5, rSV5 HNΔ2-9 (which contains an HN cytoplasmic tail truncation), and selected examples (rSV5 FΔ10 to rSV5 FΔ20) of the F protein cytoplasmic tail-truncated viruses. At 24 h p.i., cells were radiolabeled with [³⁵S]-Promix as described in Materials and Methods. Culture media and the cell lysates were harvested separately, and virions in the media were pelleted through a 35% sucrose cushion. Viral polypeptides (HN, F, NP, and M) were immunoprecipitated from both cell lysates and media as described in Materials and Methods, and polypeptides were analyzed by SDS-PAGE. The amount of M protein released into the medium was quantified and was used as a measure of viral budding competence. The percentage of total M protein in the medium was calculated from the total amount of M protein present in the cell lysate plus the medium.