A Dynamic Model of Interactions of Ca2+, Calmodulin, and Catalytic Subunits of Ca2+/Calmodulin-Dependent Protein Kinase II
Time courses of species of CaM, K•CaM, and pK•CaM with varying numbers of bound Ca2+ ions, simulated with Model 1 altered to allow binding of only CaM4 to CaMKII, and autophosphorylation of only K•CaM4.
The initial conditions were as in Figure 7. A) Time course of formation of species of free CaM. B) Time course of formation of species of CaM bound to CaMKII (K•CaM). C) Time course of formation of species of CaM bound to phosphorylated CaMKII (pK•CaM). The level of pK•CaM4 after 1 sec is 3 times lower than in the simulation with the complete Model 1 (Figure 7C). This demonstrates that the dominant pathway to pK•CaM4 at short times under these conditions is via Ca2+ binding to K•CaM species with fewer than 4 bound Ca2+ ions. The color code for Ca2+ occupation of sites on CaM is indicated on the lower left. *color code applies to all forms of CaM with the indicated bound Ca2+. Note differences in scale for panels A), B) and C).