FIG. 6.
Particle assembly in the presence of BFA. COS-1 cells transiently transfected with simian virus 40 promoter-based expression vectors were pretreated with either methanol alone (−) or with BFA (+) for 1 h. (A) SDS-PAGE analysis of immunoprecipitated wild-type and mutant Gag.GFP constructs treated with BFA. The Env-Gag fusion (SPG) contains a point mutation in PR (D37S) and appears as two protein bands within the cell and a highly glycosylated form in the medium (21). Bands corresponding to the Gag precursor Pr76gag, the cleavage proteins CA, MA, and PR, and the SPG.D37S chimera are indicated. (B) Efficiency of Gag protein release into the medium was calculated as described in Materials and Methods following either a pulse-label or 2.5-h labeling of transfected COS-1 cells. Error bars indicate the standard deviation of three or more independent experiments. Student's t test was performed to determine statistical significance (*, P = 0.027; **, P = 0.0047). WT, wild type.