Figure 3.

Free energies of unfolding for partially and fully unfolded forms of T. thermophilus and E. coli RNases H*. Each line represents the difference in free energy between the native conformation and a form in which the structural elements indicated are unfolded; the form with the highest ΔG_unf represents the fully unfolded conformation. Values of ΔG_unf were averaged for each secondary structural unit, and regions were grouped together if the average of one region overlapped with the SD for another. Strand I is not represented for T. thermophilus RNase H*; one of its three tractable residues had a ΔG_unf of 10.4 kcal/mol, whereas others were closer to the core region, both in their measured ΔG_unfs and in their location in the structure. Stabilities in 0.88 M GdmCl were calculated for T. thermophilus RNase H* residues by using the parameters in Table 1, and values for coupled regions were averaged together.