A. Schematic of variable expression cascades. The kinase concentration increases at each tier in the cascade.

B. Normalized fold increase of the high-MEK variable cascade (dark purple squares) and the basic cascade (black squares). The high-MEK variable cascade: single-copy Raf:ER expressed by P_{tetO7}, high-copy MEK expressed by P_{tetO7}, and high-copy ERK expressed by P_{Gal} (see also ). The data are the mean ± SEM, normalized to the fitted baselines. Data were fit with a modified Hill equation (solid lines).

C. Model simulations of the high-MEK variable cascade (dark purple) and the basic cascade (black). The fitted concentrations were Raf:ER = 10nM, MEK = 80nM, and ERK = 100nM.

D. Simulated Hill coefficient for the variable cascade in which both MEK and ERK were varied from 10nM to 100nM.

E. Simulated EC50 for the variable cascade for the same parameters as in D.

F. Normalized fold increase of the low-MEK variable cascade (light purple squares) and the basic cascade (black squares). The low-MEK variable cascade: single-copy Raf:ER expressed by P_{tetO7}, single-copy MEK expressed by P_{Gal}, and high-copy ERK expressed by P_{Gal}. The data are the mean ± SEM, normalized to the fitted saturation line. Data were fit with a modified Hill equation (solid lines).

G. Model simulations of the low-MEK variable cascade (light purple) and the basic cascade (black). The fitted concentrations were Raf:ER = 10nM, MEK = 30nM, and ERK = 100nM.

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