Figure 2. Equilibrium and kinetic folding behavior of UbL50E.

a) Upon acidification, the protein shifts from an intermediate to a native-like state. b) At both high and low pH, the chevron plot of UbL50E and pWTUb have nearly overlapping folding arms but distinct unfolding arms. At high pH, the UbL50E unfolding arm is shallower, suggesting disruption of β5 strand in the intermediate state. Illustrative folding energy landscapes are shown at right. Chevron values for the pWTUb have been shifted by the amount indicated by the arrows to account for the addition of 2 or 2.3 M guanidine hydrochloride required to unfold the pWTUb.