Ca²⁺-dependent coimmunoprecipitation of annexin VI with TPD52 in the Thiel myeloma cell line. Following immunoprecipitation (IP) with mAb B28p and protein G–Sepharose beads (Prt-G), proteins were analyzed by immunoblotting with murine mAbs against TPD52 (B28p, bottom panel) and annexin VI (top panel; bands in lanes 3-6 indicated by the arrowhead correspond to the heavy chains of the murine mAb B28p, detected by the secondary antimouse antibody). Coimmunoprecipitation of annexin VI (arrow in top panel) with TPD52 (arrow in bottom panel) was dependent on the presence of Ca²⁺ in the lysate (compare lanes 5 and 6).