The Role of Hydration in Protein Stability: Comparison of the Cold and Heat Unfolded States of Yfh1

Abstract

Protein unfolding occurs at both low and high temperatures, although in most cases, only the high-temperature transition can be experimentally studied. A pressing question is how much the low-and high-temperature denatured states, although thermodynamically equivalent, are structurally and kinetically similar. We have combined experimental and computational approaches to compare the high-and low-temperature unfolded states of Yfh1, a natural protein that, at physiologic pH, undergoes cold and heat denaturation around 0°C and 40°C without the help of ad hoc destabilization. We observe that the two denatured states have similar but not identical residual secondary structures, different kinetics and compactness and a remarkably different degree of hydration. We use molecular dynamics simulations to rationalize the role of solvation and its effect on protein stability.Crown

The non-uniform early structural response of globular proteins to cold denaturing conditions: A case study with Yfh1

“…Further, specifically in the case of Yfh1, the protein-water hydrogen bonds have a longer lifetime at the cold denaturing condition. 14 These results suggest that the association of water with the protein surface strengthens at cold denaturing conditions. In Figures 3(a) and 3(b), we compare water-protein g(r) obtained over the last 50 ns of the simulation trajectories at T c and T s .…”

“…This observation corroborates previous results. 14,39 In order to understand the local hydration effects upon loss of structure, we have calculated the IR absorption spectra for representative beta (S2, S4, and S5) and helical (H1) domains. A detailed inspection using IR spectra of these individual beta-sheet domains show similar trends of spectral red shifts as observed for the full protein, whereas a red shift is not observed in the calculated IR spectra of the representative helical domain of the protein upon lowering the temperature.…”

“…denaturation has been described as an irreversible process. 14 It is recognized that a clearer understanding of the origins of cold denaturation process in proteins could lead to an improved understanding of the balance of forces that lead to protein folding and stability. Under normal physiological conditions, the hydrophobic effect is a key factor underlying structural compaction incurred by a nascent, random polypeptide on the way to acquiring the folded native form.…”

“…Further, the early cold denaturation behavior of Yfh1 is fundamentally different from the early heat denaturation behavior observed at 324 K (or T h ), which is close to the experimentally reported temperature (323 K) of complete heat denaturation. 14,34 The early heat denaturation is not confined to the beta-sheet domains, and is accompanied by a strengthening of the hydrophobic effect on the protein surface.…”

Hsp60 expression profiles in the reef-building coral Seriatopora caliendrum subjected to heat and cold shock regimes

“…Moreover, an over-expression of Hsp60 protects proteins from oxidation in yeast suggesting that Hsp60 binds denatured, iron-centered proteins, preventing the release of free iron, which promotes the production of ROS through the Fenton reaction (Cabiscol et al, 2002). Furthermore, since cold stress weakens the non-covalent bonds, destabilizing the tertiary structure of proteins and causing a high rate of protein degradation (Adrover et al, 2012), the demand for chaperone-mediated protein folding could be increased. This could explain the up-regulation of Hsp60, during most of the exposure time, observed in both the cold treatments tested, which displayed the same morphological response and similar Hsp60 trends.…”