FIG. 4.

RPTPα and Src phosphorylation in HeLa cells. Unsynchronized (U) and mitotic (M) HeLa cell lysates (1 mg total protein) were split in half. One half was used to immunoprecipitate endogenous RPTPα (A). The samples and the Western blots were prepared as described for Fig. 2A. (B) The second half was used for Src immunoprecipitation. Cross-linked Src antibodies were used for this purpose. The immunoprecipitates were fractionated by 7.5% SDS-PAGE, and after transfer the membranes were probed with anti-pY416 antibody and subsequently, after stripping, with anti-npY527 and anti-Src. The experiment was performed at least three times with similar results, and a representative experiment is shown here. IP, immunoprecipitation; IB, immunoblot.