A. Superose 6 fractions (C4 and C5 from Figure 3C) of testis extracts containing co-eluted PPP1R11, PP1γ2, and Sds22 were incubated with anti-PPP1R11, anti-PP1γ2, anti-Sds22, or preimmune serum immobilized on Protein G-Sepharose 4 beads, as indicated at the top of the figure. The immunoprecipitates were separated by SDS-PAGE and immunoblotted for co-precipitating proteins as indicated below each blot strip (The reason why Sds22 migrates as a doublet is not known). B. C4 and C5 fractions of testis proteins purified by Superose 6 column chromatography were also separated by native PAGE followed by western blot analysis. Triplicated blot strips probed with either anti-PPP1R11, anti-PP1γ2, or anti-Sds22 antibodies, as indicated, demonstrate that PPP1R11, PP1γ2, and Sds22 co-migrate.