FIG. 4.

Two tyrosines in the carboxy-terminal region of PTP-HSCF are required for PTP-HSCF tyrosine phosphorylation and binding to Csk. Cells were transfected and tested as outlined in the legend of Fig. 2, with the exception that a series of PTP-HSCF mutants was used. All PTP-HSCF variants also carried the C229S mutation. The migrations of PTP-HSCF, Csk, and Lck are shown on the left. Exposures in the first and second panels were 2 and 12 h, respectively, and those in the third to fifth panels were 5 h.