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. 2022 Jan 27;8(2):282–293. doi: 10.1021/acscentsci.1c01548

Figure 2.

Figure 2

Electrostatic frustration and folding thermodynamics. (A) Tanford–Kirkwood electrostatic interaction free-energies as a function of residue number for the WT (green) and the K53E mutant (red), respectively. The shaded regions represent helical boundaries. (B) Structure of the FF1 domain highlighting the large degree of electrostatic frustration in the fourth helix. Thermal unfolding curves of the WT and the mutant from (C) near-UV CD at 280 nm, (D) far-UV CD at 222 nm, and (E) the heat capacity profiles. The dashed lines represent the corresponding pretransition baselines. The blue curve in panel C indicates the expected unfolding curve if there are no near-UV CD signal changes at the lowest temperature for the K53E mutant. (F) The slope of the pretransition baseline (dashed lines in panel E) compared with those of conformationally heterogeneous DNA binding domains (DBDs; triangles) and well-folded proteins (small filled circles). The continuous and dashed horizontal lines signal the Freire baseline slope and one standard deviation, respectively. Note that the mutation K53 → E53 changes the slope significantly.