FIGURE 3.

Activity of purified MbSrc1. A, MbSrc1 (0.7 μm) was screened with various synthetic peptides (200 μm) using the phosphocellulose paper assay. The reactions proceeded for 20 min at 30 °C and were analyzed by scintillation counting. PKA, protein kinase A; EGFR, epidermal growth factor receptor; InsR, insulin receptor. B, MbSrc1 (0.7 μm) was assayed with the Src substrate peptide (200 μm) alone or in the presence of pYEEI peptide (88 μm) or the Pro-rich peptide (200 μm) for 10 min at 30 °C. For the ATP reaction, MbSrc1 (4.6 μm) was first preincubated with ATP (0.5 mm) for 45 min at 4 °C.