FIGURE 1.

MP complex: specific interaction of MYPT1 with the β isoform of PP1c. A, organization of the individual components of MP is shown (see the Introduction for details). B, GFP-tagged expression plasmids for the three isoforms of PPIc and Myc-tagged expression plasmids for wild-type and F38A-mutated MYPT1 were co-expressed in HeLa cells for 1 day, lysed, and immunoprecipitated using anti-GFP antibodies. The immunoprecipitant was then analyzed using SDS-PAGE and Western blotting to assess the extent to which Myc-tagged MYPT1 was co-immunoprecipitated with the GFP-tagged PP1c proteins (bottom panel). A portion of the lysate was retained for each sample and electrophoresed and blotted (IB) separately to demonstrate the total levels of expression of the Myc-tagged MYPT1 and GFP-tagged PP1c proteins (top two panels). Experiments present in this and subsequent figures were repeated three or more times unless otherwise noted. Representative Western blots are shown.