Fig. 8. Phosphorylation of PCBP-25, PCBP-25ß and CaM by purified Ca²⁺-dependent protein kinases. CaPK-1 and CaPK-2 were purified by chromatography on phenyl-Sepharose and MonoQ. MonoQ-purified PCBP-25, PCBP-25ß and CaM were incubated with [-³²P]ATP and either (A) CaPK-1 or (B) CaPK-2 (20 units each) for 30 minutes in the absence or presence of Ca²⁺ (13.5 µM free) according to the Materials and Methods. Lanes 1 and 2, 1 µg PCBP-25; lanes 3 and 4, 1 µg PCBP-25ß; lanes 5 and 6, 2 µg concentrated, desalted CaM. Arrows indicate autophosphorylation of CaPK-1 or CaPK-2 and phosphorylation of PCBP-25ß and CaM.