Figure 2.

GDI binding of Rac1 is not dependent on postprenylation CAAX processing. MEFs expressing (+/+) or deficient (–/–) in Icmt or Rce1 were transfected with GFP-Rac1. GFP-Rac1 was immunoprecipitated from cell lysates with anti-GFP antibodies and analyzed by SDS-PAGE and ¹²⁵I-protein A immunoblot for GFP and for RhoGDI. (A) Representative coimmunoprecipitation with recombinant RhoGDI (rRhoGDI) as a control run on the same gel (shown as separate panel because of a much lower PhosphorImager exposure time). The identity of the nonspecific band running slightly higher than RhoGDI is not known. (B) Cumulative data where the ability of RhoGDI to interact with GFP-Rac1 is quantified by coimmunoprecipitation as the PhosphorImager volumes of [GDI]/[GFP-Rac1], and the data are normalized across experiments by assigning a value of 1 to ratios from Icmt +/+ cells. Bars shown are mean ± SEM, n = 6.