FIG 5 .

Most PP1 regulatory proteins bind to PPZ1 less effectively. (A) Domain structure of the regulators tested (G34, GADD34_552–567; PNUTS, PNUTS_394–433; Spino, spinophilin_417–602) with their canonical PP1 interaction motifs highlighted in different colors. (B) Structures of the GADD34 (blue; PDB no. 4XPN [26]), PNUTS (orange; PDB no. 4MOY [19]), and spinophilin (gray; PDB no. 3EGG [27]) PP1 holoenzymes, with close-ups of the Z1 helix interaction pocket. (C) The relative binding of PP1α and PPZ1 with the regulators described in panel A was determined using a pulldown assay. (D) Densitometry analysis of the gel in panel B. (E) Binding isotherm of GADD34_552–567 with PPZ1_cat (K_D, 1,150 ± 90 nM). (F) Dose-response curves of phosphatase activity with increasing concentrations of I-2 with PP1_c, PPZ1_cat, and PPZ1_FL phosphatases. The data represent the means ± SE from 3 experiments.