FIG. 3.
Mutation of the PPPY motif reduces VLP production. (A) Amino acid substitutions to the conserved PPPY sequence. The PrGag is shown as described for Fig. 4. The amino acid sequence of PPPY domain and its flanking sequence are expanded. The full-length black line represents the wt Gag sequence. The alanine substitutions are indicated below and are aligned with the expanded sequence. The name of each mutant is indicated on the left. (B) Analysis of VLP production. COS-1 cells or 293 cells were stably transfected with pGag-HA or the indicted mutants. Cell and VLP lysates were analyzed by Western blot using an anti-HA Ig. The Western blots were subjected to quantitative fluorochemical analysis as described in the text. This experiment was repeated three times, with representative results shown.