B: Rac1 interaction with FIP3: HEK293T cells were transfected with GFP, GFP-FIP3 WT or GFP-FIP3I738E expression vectors. 24 h later, cells were lysed and immunoprecipitated with anti-GFP Ab. Immunoprecipitates were analyzed by electrophoresis and western blot using anti-GFP Ab (top panel) or anti-Rac1 Ab (bottom panel). Total cell lysates were analyzed (100,000 cells). The position of Rac1 (20 kDa) and Ig light chain (25 kDa) polypeptides is depicted on the right side. Arrowheads at the bottom point the bands corresponding to Rac. Quantification of bands was performed with ImageJ as the percentage of intensity with respect to the total lysate bands on the left, shown below. A representative experiment out of three carried out is shown. 