Fig. 6.

Kinetic analysis of p38 MAPK-mediated phosphorylation of MK2, MK3 and MK5. Different amounts of purified GST-MK3.1 (A), GST-MK3.2 (B), GST-MK2 (C), or GST-MK5 (D) were incubated with the phosphorylated, activated forms of p38α (■), p38β (●), p38δ (▲), or p38γ (▼). A time course of ³²P incorporation was performed at 30 °C for each indicated [S] as described in Materials and methods. Following phosphorylation, samples were solubilized using SDS-PAGE sample buffer and separated using SDS-PAGE. Gels were stained with Coomassie Brilliant Blue R-250, dried, the substrate band excised, and ³²P incorporation determined by liquid scintillation counting. The specific activity of the [γ³²P]ATP was determined for each experiment.