Figure 4.

Fitting the simulated stabilities and folding rates of the modified ANK and TPR proteins to a simple capillarity model. (A) Correlation among folding stability, the number of repeat units (n), and the ratio between E_Inter and E_Intra, λ. The folding temperatures (normalized by the T_F of a protein with a single repeat) of each modified and unmodified TPR and ANK repeat (λ = 0.7, 1.0, and 1.3 in various systems) with a different number of repeat units (n) are plotted as a function of (n − 1)/n. All of the systems fit a linear function with correlation coefficients > 0.95. The slope of the linear fits, which corresponds to λ, is in very good agreement with the value of λ used in the simulation (c = 5). The inset shows a comparison between the experimental and simulated folding temperatures of a series of unmodified TPR proteins comprising 2–10 repeat units (correlation coefficient R = 0.96). (B) Correlation among the simulated folding rates, n, and the strength of the interface. The folding rate is plotted as a function of (1 − 2/n). The simulated data of the six series fit linear functions with correlation coefficients > 0.9. The slope of the linear fit, which corresponds to E_Inter, is similar to the value used in the simulations (when a is assigned a value of 10). The values of E_Inter in the simulation model are 58, 45, and 33 for ANK, and 58, 43, and 33 for TPR (where the large numbers refer to the systems with larger λ values). The color scheme is the same as that used in Fig. 1D.