Fig. 5.

In vitro phosphorylation of candidate substrates by mitogen-activated protein kinases. Selected candidate proteins (GFP-δ-catenin, GFP-PKP4, FLAG-4.1N, FLAG-AbLIM1, FLAG-MAGI-2, FLAG-SAPAP4, FLAG-PIP5K1C, and FLAG-SynGAP1) were expressed in HEK293 cells, immunoprecipitated with epitope tag antibodies, and incubated with γ-[P32]ATP and different recombinant active MAPKs as indicated. Phosphorylation was visualized by autoradiography. FLAG-tagged transcription factor Elk-1 is used as positive control (see “Results”).