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The figure shows the simplified wiring of the cascade (top) from Ras to Erk and its

activation over time (input → signal path → output) as well as its mathematical description

(bottom). Here, the concentration of the activated kinase (X) depends on the time (t). In

addition, α describes the phosphorylation, β the corresponding dephosphorylation and C

the total concentration of the kinase. This formula can be used to describe the whole cas­

cade in a simplified way and then model it in the computer, for example to better ­understand

tumor growth (e.g., how does overexpression of the kinase affect proliferation or to derive

new therapeutic approaches). For more information, see also Robubi et al. (2005) B-Raf

and C-Raf signaling investigated in a simplified model of the mitogenic kinase cascade.

Biol Chem. 386(11): 1165–1171.

20.7  How to Better Understand Signal Cascades and Measure the Encoded Information