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. Author manuscript; available in PMC: 2012 Jan 23.
Published in final edited form as: Methods Enzymol. 2011;492:27–59. doi: 10.1016/B978-0-12-381268-1.00014-8

Figure 2.12.

Figure 2.12

MWC model for eukaryotic action at a distance. The regulatory region of the DNA is pictured here to have seven distinct binding sites. The organization of the DNA itself is further posited to exist in two different states. Following the MWC philosophy, the binding energy of the transcription factors (pictured here as triangles) depends upon whether the DNA is in the “closed” or “open” state. (A) States and weights corresponding to the model. (B) Data for the normalized level of Hunchback protein as a function of the level of Bicoid protein (Gregor et al., 2007) measured in units of [Bcd1/2], the concentration of Bicoid protein for which [Hb]/[Hbmax] = 1/2, overlaid with a fit to a Hill function [Hb]/[Hbmax] = b(1 + f([Bcd]/Kd)5)/(1 + ([Bcd]/Kd)5) and the MWC model shown in Eq. (2.11). The parameters of the Hill function are b = 0.01, f = 99, and Kd = 0.88. For the MWC model, we took the limit Kd(inactive) → + ∞ and used the parameters Kd(active) = 0.3, and Δε = εactive − εinactive = 9.5 kBT.