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arXiv · 1503.03716

Role of solvation in pressure-induced helix stabilization

Robert B. Best·Cayla Miller·Jeetain Mittal
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Abstract

In contrast to the well-known destabilization of globular proteins by high pressure, re- cent work has shown that pressure stabilizes the formation of isolated α-helices. However all simulations to date have obtained a qualitatively opposite result within the experimen- tal pressure range. We show that using a protein force field (Amber03w) parametrized in conjunction with an accurate water model (TIP4P/2005) recovers the correct pressure- dependence and an overall stability diagram for helix formation similar to that from experi- ment; on the other hand, we confirm that using TIP3P water results in a very weak pressure destabilization of helices. By carefully analyzing the contributing factors, we show that this is not merely a consequence of different peptide conformations sampled using TIP3P. Rather, there is a critical role for the solvent itself in determining the dependence of total system volume (peptide and solvent) on helix content. Helical peptide structures exclude a smaller volume to water, relative to non-helical structures with both the water models, but the total system volume for helical conformations is higher than non-helical conformations with TIP3P water at low to intermediate pressures, in contrast to TIP4P/2005 water. Our results further emphasize the importance of using an accurate water model to study protein folding under conditions away from standard temperature and pressure.

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Robert B. Best, Cayla Miller, Jeetain Mittal. 2015-03-12. Role of solvation in pressure-induced helix stabilization. https://doi.org/10.1063/1.4901112

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