FIG. 2.

PKA phosphorylates MEF2D directly in vitro. (A) Purified GST-MEF2D (MADS-MEF2 domain [aa 1 to 86 or 87 to 507]) was incubated in vitro, with or without purified PKA, with [γ-³²P]ATP, resolved using SDS-PAGE, visualized by Coomassie blue staining, dried, and exposed to X-ray film for 16 h after the PKA kinase assay. (B) Several cognate PKA phosphoacceptor sites were identified on mouse MEF2D by the consensus sequence (R/K)₂X(S/T) or (R/K)X(S/T). (C) Ser 121 is highly conserved between MEF2D proteins from the mouse, human, rat, and frog. Residue coordinates are labeled according to mouse MEF2D.