FIG. 6.

RKIP binding to Raf-1 or MEK is sufficient for inhibition. (a) Coimmunoprecipitation of RKIP deletion mutants with Raf-1. FLAG–Raf-1 and hemagglutinin (HA)-RKIP or HA-RKIP deletion mutants were coexpressed in COS cells. Lysates were immunoprecipitated (IP) with anti-FLAG antibodies, and associated HA-RKIP proteins were detected by Western blotting (WB) with anti-HA antibodies. PEB, phosphatidylethanolamine binding motif. (b) The effect of RKIP deletion mutants on Raf-induced AP-1 reporter gene expression. HA-RKIP mutants were cotransfected with the Raf-1 kinase domain, BXB, and an AP-1–luciferase plasmid.