FIG. 4.
Characterization of Ser→Ala mutants. (A) Scheme of Δ1/Δ3 mutant showing positions of the four serines mutated to alanine within region 4. The residue numbers correspond to the wild-type protein. (B) Immunoprecipitates of in vivo 32Pi-labeled MA104 cells transfected with nonmutated (−) or with the indicated mutant constructs. The numbers refer to mutated Ser residues. (C) Western immunoblot of λ-Ppase-treated (+) transfected Δ1/Δ3 mutant. (D) Phosphorylation with [γ-32P]ATP of GST-Δ1/Δ3 and GST-Δ1/Δ3(S→A) as for Fig. 3.