Figure 3.

Effect of cdk5 phosphorylation on the rate of its activation by p25. GST-cdk5 was phosphorylated by a PC12 lysate (4-h incubation time), followed by adsorption on glutathione-Sepharose and washing as described in Experimental Procedures. Parallel control samples were carried through the procedure in the absence of lysate. Aliquots of the GST-coupled phosphorylated (▴) or unphosphorylated (●) cdk5 samples were preincubated with GST-p25 for different times followed by measurement of histone kinase activity as described in Experimental Procedures.