FIGURE 11.

Ser-621 of C-RAF BxB is necessary for its dimerization with B-RAF and for its kinase activity. HA-tagged C-RAF proteins were immunoprecipitated (IP HA) from protein lysates of HEK 293 cells that were transfected with the indicated expression plasmids. The kinase activity of immunoprecipitated C-RAF BxB proteins was measured as the ability to phosphorylate purified ERK-2 in vitro as reported under “Experimental Procedures.” IPs, kinase assays, and total lysates were gel separated and immunoblotted with the indicated antibodies.