A ternary complex of DNase I, G-actin, PP1G and PPP1R15A retains its eIF2a P -directed phosphatase activity. ( A ) UV protein absorbance trace of a PPP1R15A (539–614)-PP1G(7–323)-G-actin and DNase I complex assembled from the bacterially-expressed binary complex, rabbit muscle G-actin and bovine pancreatic DNase I, resolved by size-exclusion chromatography. The indicated fractions from the chromatogram are presented in the Coomassie-stained SDS-PAGE below. The positions of G-actin, PP1, DNase I, and the PPP1R15A peptide are indicated. ( B ) Cartoon representation of a model of the PPP1R15B, PP1G, and G-actin ternary complex with DNase I placed by superimposing the actin and DNase I complex (PDB: 2A41) ( Chereau et al., 2005 ) onto the PPP1R15B, PP1G and G-actin ternary complex (PDB: 4V0U). Note that DNase I is bound to the backside of the ternary complex, facing away from the PP1 active site (arrow). ( C ) Images of Coomassie-stained Phos-Tag SDS-PAGE in which phosphorylated and dephosphorylated eIF2a (eIF2a P and eIF2a 0 ) have been resolved. Escalating amounts of G-actin or a complex of G-actin and DNase I (final concentration, 10 nM–1 µM) were added to a reaction containing 25 nM PPP1R15B-MBP and PP1G complex (as in Figure 3A ) and 2 µM eIF2a P substrate for 20 min. DOI: http://dx.doi.org/10.7554/eLife.04871.022 