FIG. 3.

Effect of protease cleavage site mutations on proteolytic processing of precursor proteins. (A) Sequence of the PR-TFP part of the Gag-Pro precursor. The previously mapped cleavage site Psite1 (VIL/PIQ,) is indicated by a single downward arrow. Two arrows indicate the possible cleavage sites in Psite2. The sequences encoded by the mutants at the sites are indicated below the arrows. Samples were generated and processed as described in the legend for Fig. 1. Lane 1 contains the mock-transfected control. The provirus constructs used were pX1MT derived with either no mutation (lane 2), a Psite1 mutation (lane 3), a Psite2 mutation (lane 4), or both mutations (lane 5). (B to D) Immunoblots probed with anti-TFP (B), anti-PR (C), or anti-p19 (MA) (D). The arrows in panels B and C indicate the TFP and PR bands, respectively.