Regulatory interactions of the calmodulin-binding, inhibitory, and autophosphorylation domains of Ca2+/calmodulin-dependent protein kinase II.

Two peptide analogs of Ca2+/calmodulin-dependent protein kinase II (CaMK-(peptides)) were synthesized and used to probe interactions of the various regulatory domains of the kinase. CaMK-(281-289) contained only Thr286, the major Ca2+-dependent autophosphorylation site of the kinase (Schworer, C. M., Colbran, R. J., Keefer, J. R. Vmax = 3.15 mumol/min/mg) for the proteolyzed kinase whereas phosphorylation of CaMK-(281-309) showed nonlinear Michaelis-Menton kinetics, with maximal phosphorylation (0.1 mumol/min/mg) at 20 microM and decreased phosphorylation at higher concentrations. The addition of Ca2+/calmodulin to assays stimulated the phosphorylation of CaMK-(281-309) by the proteolyzed kinase approximately 10-fold but did not affect the phosphorylation of CaMK-(281-289). A model for the regulation of Ca2+/calmodulin-dependent protein kinase II is proposed based on the above observations and results from other laboratories.