Fig. 7. Co-immunoprecipitation of ß₅ integrin with Sdc1 requires the Sdc1 ectodomain. Western blots probed with rabbit polyclonal ß₅ integrin (A,B), pan-syndecan or S1ED (C) antibody for detection of ß₅ integrin and Sdc1, respectively, in immune complexes isolated after immunoprecipitation of full-length mouse Sdc1 (mAb 281.2), human Sdc1 constructs (mAb B-B4) and FcR^ecto-hS1 chimera (mAb 10.1) from pre-cleared B82L whole-cell lysates. In S1ED-competition experiments (A), 30 µM soluble GST, GST-mS1ED (with mAb B-B4) or GST-hS1ED (with mAb 281.2) was added to the reaction mixture. Provided as a reference is a methanol precipitation (MeOH) of 300 µg of whole-cell lysate. ß₅ integrin immunoblotting reveals a 110 kDa band, under reduced conditions, detectable in the mouse Sdc1 and select human Sdc1 (hS1, pLTM, cyto), but not FcR^ecto-hS1 chimera immunoprecipitates or immunoprecipitates isolated with antibody isotype control IgG: mouse IgG₁ (mIgG) for mAbs B-B4 and 10.1 and rat IgG2A (rIgG) for mAb 281.2.