FIGURE 8. Selectivity of MKK7 D-site interaction with JNK versus ERK.

A, D-site peptides (triangle) were used to inhibit JNK1 or ERK2 (MAPK) phosphorylation of the c-Jun, ATF2, or Elk-1 transcription factors (TF). B and C, inhibition of JNK1-dependent phosphorylation of c-Jun. The details are as described for Fig. 7, B and C, respectively. D and E, inhibition of JNK1-dependent phosphorylation of ATF2. The details are as in Fig. 7, D and E. F, inhibition of ERK2-dependent phosphorylation of Elk-1. Purified GST-Elk-1 (1 µm) was incubated with purified active ERK2 (~1 nm) and [γ-³²P]ATP for 20 min in the absence or presence of the specific concentrations of the indicated peptides (see Table 3). Results are plotted as percent phosphorylation relative to that observed in the absence of any added peptide. Elk-1 phosphorylation was analyzed by SDS-PAGE and quantified on a PhosphorImager. Data are the average of at least two experiments, with duplicate data points in each experiment.