Figure 1.

CIB1 binds to PAK1 in vivo and in vitro. (A) Immunoprecipitates from platelet lysates were immunoblotted with an antiphosphoserine (left) or anti-PAK (middle) antibody. Whole cell lysates (WCL) were probed with an anti-PAK antibody (right; n ≥ 3 experiments). (B) CIB1 and control IgY immunoprecipitates from lysates of REF52 cells in suspension or adhered to FN were immunoblotted for PAK (top) and CIB1 (bottom). (C) Solid-phase binding assays using immobilized CIB1 and soluble PAK proteins. Increasing concentrations of His-PAK1 were added to wells coated with and without immobilized CIB1. His-PAK1 binding was detected using an anti-His antibody. (D) PAK isozyme–binding specificity was determined by adding GST-PAK1 or GST-PAK2 to immobilized CIB1. PAK binding was detected with an anti-GST antibody. WB, Western blot; IP, immunoprecipitates. Error bars represent SEM.