Figure 3.

Existence of an optimal scaffold concentration. (A) Dependence of MAPK activation (red) and functional scaffold–kinase complexes C₆ (blue) and C₈ (dashed magenta) on the two-member scaffold concentration. MAPK activation at 100-fold lower MAPKK phosphatase concentration is shown in light blue. C₆ is normalized by dividing by 40 and C₈ by multiplication by 17 for better comparison and illustration purposes. The results are compared with the plot of 0.15/[Scaffold] (green). (B) The optimum of MAPK activation or C₆ formation is not sensitive to the dissociation constant K_D of MAPK–scaffold interaction. The lighter areas in the contour plots correspond to higher MAPK or C₆ concentrations. (C and D) The optimal scaffold concentration (two-member scaffold) is a function of MAPKK (C) and MAPK (D). Both three-dimensional and contour plots of MAPK activation are shown.