Figure 6

S phase entrance rate vs Cki relative concentration depending on the translocation of binary and ternary cyclin/Cdk complexes. The level of phosphorylated S phase activator at the end of the simulation (taken as a measure of the G₁ to S transition) is shown as a function of relative Cki concentration at the beginning of the simulation. Three cases are presented: rate constants for the cytoplasm-to-nucleus translocation of binary and ternary cyclin/Cdk complexes are equal (blue line); the rate constants for the ternary complexes is 5-fold higher compared to the binary complexes translocation constants (pink line, corresponding to our standard simulation parameter set); the rate constants for the ternary complexes is 25-fold higher compared to the binary complexes translocation constants (green line).