Figure 2.

CAP1 is not a Rap1b effector protein. A, nucleotide-independent Rap1–CAP1 interaction. Lysates expressing HA-Rap1b were loaded in vitro with GDP or GTPγS, and a binding assay was performed upon incubation with myc-CAP1 immobilized on beads. B, Rap1 activation was monitored by GST-RalGDS-RBD pulldown assay. C, HA-CAP1 interacted equally with WT, constitutively active (G12V), and dominant negative (S17N) Rap1 proteins. D, effector domain (ED) mutations in switch I did not affect the interaction between CAP1 and Rap1b. Representative experiments (n = 3) are shown. V, empty vector.