(A) COS-7 cells were co-transfected with plasmids expressing myc–PP2Cδ(H154D,T333A) and truncated HA–RSK2 mutants. Transfection of myc–PP2Cδ(H154D,T333A) without HA–RSK was used as a control. HA–RSK2 was precipitated from the cell lysates with anti-HA antibody, washed five times and subjected to SDS/PAGE followed by immunoblotting with anti-myc or anti-HA antibody. The cellular expression level of PP2Cδ(H154D,T333A) was determined by immunoblotting of lysates with anti-myc antibody. (B) COS-7 cells were co-transfected with plasmids expressing truncated myc–PP2Cδ(H154D,T333A) and HA–RSK2. Transfection of myc–PP2Cδ(H154D,T333A) without HA–RSK2 was used as a control. HA–RSK2 was precipitated from the cell lysates with anti-HA antibody. The precipitates were washed five times and the samples were subjected to SDS/PAGE followed by immunoblotting with anti-myc or anti-HA antibody. The expression level of PP2Cδ in the cells was determined by immunoblotting of lysates with anti-myc antibody.