A) Identification of a PKA phosphorylation site RRDSD in a target protein X by in silica analysis.

B) Plasmids expressing the WT protein, or the protein with the S > A mutation in the RRDSD motif, or the protein with a S > A mutation in an irrelevant site were used to transfect HeLa cells. Cell lysates were collected for evaluating the expression level of the whole and phosphorylated protein by Western blot.