Scambio does not stimulate guanine nucleotide exchange on Rac and Cdc42 (A) Cells were transiently transfected with either vector, wild type Rac3 (Xpress-tagged), wild type Rac3 and Dbl, or wild type Rac3 and Sabi. The GST-pull downs (left panel) were immunoblotted with anti-Xpress antibodies. Lysates (right panel) were immunoblotted with anti-Xpress, anti-HA, and anti-GST antibodies to detect Xpress-tagged Rac3, HA-Sabi, and GST-Dbl, respectively. (B) Cells were transfected with either vector alone, wild type Cdc42 (Xpress-tagged), wild type Cdc42 and Dbl or wild type Cdc42 and Sabi. The GST-pull downs for Cdc42 (left panel) and lysates (right panel) were treated as described for Rac3.