Western blot of human T47D cells using C2549-50M showing specific immunolabeling of the ~34kD cdc2 phosphorylated at Tyr15 (Control, Lane 1). Treatment with EGF (30ng per ml for 30 min) caused dephosphorylation of the Tyr15 on cdc2 (Lane 2). Phosphospecificity is shown in lanes 3 and 4, where the immunolabeling is completely eliminated by blot treatment with lambda phosphatase, λ-Ptase (1200 units for 30 min).