Fig. 5. ERK activation. (A) Stimulation of ERK phosphorylation in raf-1^+/+, raf-1^–/– and raf-1^FF/FF MEFs over a time course of EGF treatment. (B) Stimulation of ERK phosphorylation in raf-1^+/+, raf-1^–/– and raf-1^FF/FF MEFs following treatment with different stimuli for 10 min. The blots in (A) and (B) were incubated with an anti-phosphoERK antibody (top panels) and an anti-ERK2 antibody (bottom panels) to control for protein loading. (C) ERK activation in raf-1^+/+, raf-1^–/– and raf-1^FF/FF MEFs over a time course of EGF treatment as measured by the immunocomplex MBP kinase assay. (D) ERK activation in raf-1^+/+, raf-1^–/– and raf-1^FF/FF MEFs following stimulation with different concentrations of EGF for 10 min as measured by the MBP kinase assay.