FIG. 3.

Analysis of Erk2 activity in NIH 3T3 and Rat 6 cells that express H-Ras 12V and various effector loop mutants. Cells expressing the indicated constructs were cultured in methylcellulose and harvested. Erk2 was immunoprecipitated and assessed for activity with myelin basic protein (MBP) as a substrate as described in Materials and Methods. Erk2 levels in each cell type were also assessed by Western blotting with anti-Erk2 antibodies. The numbers below the MBP kinase assay represent relative activities derived by densitometric analysis of the signal, with the neo lane designated 1.