FIG. 4.

PATH estimates of ΔG_conf (14) are closely correlated with the structural differences between virtual variants. PATH estimates of ΔG_conf were obtained from the TOR_IM and AMWEH_IM algorithms and scaled by regression methods to account for differences between the all-atom TOR_IM (all atom) and AMWEH_IM (CA only) Hessians. Their units and those on the Y axis here are in arbitrary units. The histogram shows coefficients (in the same arbitrary units) for the regression model relating these ΔG_conf values to the presence or absence of mutated sites in the virtual mutants. The most important contributor is the four-way interaction between I4 and the three aromatic side chains. The sign of this interaction indicates that, together, they make the overall ΔG_conf less favorable, which is consistent with the experimental estimate and with the fact that the mutations were selected by the Rosetta multistate algorithm to reduce the free energy change between PreTS and Product states. The inset shows that the histogram is virtually identical to that obtained by fitting the TOR_IM derived ΔG_conf values alone, for which the equal number of data and parameters precludes estimation of errors.