PfPP1 dose response to inhibitors. Inhibition assays for recombinant PfPP1 were performed using 32P-phosphorylase a as substrate essentially as described . The inhibitors and the symbols are: tautomycin (square), inhibitor-2 (diamond), OA (triangle), and I-1 (circle). The half-closed and fully closed diamonds represent I-2 against the double mutant (E52A/E54A) and triple mutant (D164A/E165A/K166A) enzymes, respectively. Activities are expressed as percentage of the inhibitor-free reaction. As shown, the X-axis represents negative logarithm of molar concentration of the inhibitors.