Unraveling the Molecular Mechanism of Enthalpy Driven Peptide Folding by Polyol Osmolytes

Abstract

Many polyols and carbohydrates serve in different organisms as protective osmolytes that help to stabilize proteins in their native, functional state, even under a variety of environmental stresses. However, despite their important role, much of the molecular mechanism by which these osmolytes exert their action remains elusive. We have recently shown experimentally that, although polyols and carbohydrates are excluded from protein and peptide interfaces, as also expected for the known entropic "crowding" mechanism, the osmolyte folding action can in fact primarily be enthalpic in nature. To follow this newly resolved enthalpically driven stabilization mechanism, we report here on molecular dynamics simulations of a model peptide that can fold in solution into a β-hairpin. In agreement with experiments, our simulations indicate that sorbitol, a representative polyol, promotes peptide folding by preferential exclusion. At the molecular level, simulations further show that peptide stabilization can be explained by sorbitol's perturbation of the solution hydrogen bonding network in the peptide first hydration shells. Consequently, fewer hydrogen bonds between peptide and solvating water are lost upon folding, and additional internal peptide hydrogen bonds are formed in the presence of sorbitol, while internal peptide and water-associated hydrogen bonds are strengthened, resulting in stabilization of the peptide folded state. We further find that changes in water orientational entropy are reduced upon folding in sorbitol solution, reflecting the struggle of water molecules to maintain optimal hydrogen bonding in the presence of competing polyols. By providing first molecular underpinnings for enthalpically driven osmolyte stabilization of peptides and proteins, this mechanism should allow a better understanding of the variety of physical forces by which protective osmolytes act in biologically realistic solutions.

Cosolute Effects on Amyloid Aggregation in a Nondiffusion Limited Regime: Intrinsic Osmolyte Properties and the Volume Exclusion Principle

“…Preferential inclusion/exclusion, which can be an interpretation of Γ µ , is a well-studied mechanism for osmolyte effects on aggregation. 6,14,18,36,37,49,51,52 The correlation shown in Fig. 6A supports this mechanism.…”

“…6A). 32,34,35,36,49 However at C GuHCl > 0.6 M, the aggregation effects of GuHCl are different from C GuHCl < 0.6 M (Figs. 1A & 3).…”

“…32,49 The osmolyte with the largest stabilizing effect, TMAO, is known to affect protein stability through multiple mechanisms. 32 Here we showed that TMAO was the most stabilizing in terms of lowering k mon and k nu (Fig.…”

Single-injection vaccines: Progress, challenges, and opportunities

“…Many groups have added non-reducing sugars such as trehalose or polyols like sorbitol to stabilize secondary antigen structure during device formulation [144][145][146][147][148]. While the mechanisms by which these osmolytes function has yet to be conclusively determined, prevailing theories center on water exclusion and improved hydrogen bond strength that makes conformational changes away from the native state even more energetically unfavorable [149][150][151]. Most of these compounds appear to minimize antigen damage during both drying and after they are implanted into the body.…”

Arginine inhibits aggregation of α-lactalbumin but also decreases its stability: Calorimetric, spectroscopic, and molecular dynamics studies

“…Therefore, overall effect of Arg on the structure of water might be negligible. Hence, it can be inferred that the direct interaction of Arg through its guanidinium group with the protein leads to inhibition of aggregation and decrease in the stability the protein.The value of the preferential interaction coefficient (C XP ) of the guanidinium group of Arg was calculated by using the following equation [46][47][48][49]:…”