Figure 1.

Inhibition of wild-type Sf9 cell PP1 and PP1/PP2A chimera by thiophospho-DARPP-32 and inhibitor-2. Phosphatase activity of wild-type PP1 (closed and open circles) and PP1/PP2A chimera (closed and open squares) was measured in the absence (closed symbols) or presence (open symbols) of 20 μM PNUTS[392–408] peptide and the indicated concentrations of thiophospho-DARPP-32 (A), or inhibitor-2 (B). Phosphatase activity was measured by using 10 μM [³²P]phosphorylase a as substrate. Phosphatase activity is expressed as percent of activity measured in the absence of protein inhibitors.