Truncation of platelet GP Ibα at Tyr605 ablates the interaction between GP Ibα and 14-3-3ξ. (Left) Western blot of platelet lysates detecting 14-3-3ξ protein at approximately 32 kDa in human platelets, mouse platelets, and mouse platelets expressing human GP Ibα subunits but devoid of mouse GP Ibα (hTg^WT and hTg^Y605X). The experiment demonstrated that total levels of 14-3-3ξ were similar in each of the samples. (Right) Results obtained after immunoprecipitation of human GP Ibα. Bound anti–14-3-3ξ antibody was detected using radiolabeled goat anti–rabbit IgG. Results demonstrate that the truncation of GP Ibα ablated the interaction with 14-3-3ξ, as evidenced by the lack of 14-3-3ξ antigen. Longer exposures of the autoradiograph failed to detect any 14-3-3ξ antigen in the hTg^Y605X sample. The same nitrocellulose filter was probed a second time with an anti–human GP Ibα monoclonal antibody, LJ-Ibα1, and demonstrated the presence of GP Ibα antigen in those samples in which the human subunit was present (bottom panel).