FIG. 6.

Characterization of BIT- and PIR-B-associated proteins. (A) BIT and PIR-B associate with a PTK activity in primary BMM. BIT and PIR-B from normal and me/me primary BMM were assayed for autokinase activity for the times indicated and analyzed by autoradiography (left panel) and anti-pTyr immunoblotting (right panel). Assay conditions are described in Materials and Methods. The migration of molecular size standards is indicated in kilodaltons at the left. IP, immunoprecipitation. (B) V8 endoprotease mapping of BIT- and PIR-B-associated P55 and P120 proteins. The autophosphorylated 55- and 120-kDa proteins from radiolabeled anti-SHPS-1 and anti-PIR-B immune complexes were excised from gels and subjected to in gel treatment with the indicated amounts of V8 protease as described in Materials and Methods. Labeled digests were analyzed by SDS-PAGE (15% gel) and autoradiography. The migration of molecular size standards is indicated in kilodaltons at the left of each panel.