TPR-dependent activation of PfPP5 by unsaturated fatty acids. Phosphatase assays were performed using 32P-phosphohistone substrate as described under Materials and Methods. The activities were expressed as the ratio of that obtained in the absence of any fatty acid, taken as 1. The following PfPP5 preparations were tested against the indicated fatty acids: recombinant ΔTPR-PP5 (open triangle); trypsin-treated recombinant PfPP5 (corresponding to lane 7 in Fig. 3; filled triangle); and recombinant PfPP5 (all the others).