FIGURE 4.

Effector-induced changes in the Switch I conformation of GMP-PCP-bound Cdc42. A, addition of the limit Cdc42/Rac-binding domain of Pak3 (PBD) (1 μm) to GMP-PCP-bound Cdc42(Y32W,W97H) (1 μm) causes a quenching of Trp-32 fluorescence. B, addition of the PBD to GDP-bound Cdc42(Y32W,W97H) has no effect on Trp-32 fluorescence. C, titration of GMP-PCP-bound Cdc42(Y32W,W97H) with increasing amounts of Pak3-PBD(W98F) (0.2-4 μm). The addition of PBD(W98F) decreases the quantum yield of the Cdc42 mutant until it reaches saturation at roughly 80% of the original intensity.