CMS and CIN85 interact with the polyproline-arginine sequence within the human pTα tail through different SH3 domains. Schematic representation of Flag-tagged CIN85 (A) and CMS (B) forms used in pull-down assays shown in panels C and D, respectively. Pull-down assays were performed with GST fusion proteins of either the wild-type pTα cytoplasmic tail (GST-pTα) or the indicated proline-rich deletion mutants (GST-pTαΔPro1, GST-pTαΔPro2, and GST-pTαΔPro3). Precipitated proteins were analyzed by Western blotting with an anti-Flag mAb. Data are representative of at least 3 independent experiments. Vertical lines have been inserted to indicate a repositioned gel lane.