Fig. 3.
The Noonan syndrome mutation E108K activates Sos by increasing PA-binding and membrane association. (A) Sos-H (closed circles) and Sos-HE108K (open circles) were incubated with 1 mM PA-containing lipid vesicles and affinities calculated as in Fig. 1D. (B) GFP-tagged Sos-H or Sos-HE108K were transfected into COS-1 cells and membrane localization quantified as in Fig. 1E. Results are mean ± s.d. of three independent experiments. (C) COS-1 cells were cotransfected with HA-tagged Ras and either HA-tagged Sos or SosE108K. Cells were serum starved and then stimulated with 10 nM EGF for the indicated intervals and RBD pull-down performed as in Fig. 2. Results are mean ± s.d. of three independent experiments. ∗,P < 0.05.