A Tale of Two Desolvation Potentials: An Investigation of Protein Behavior under High Hydrostatic Pressure

Hydrostatic pressure is a common perturbation to probe the conformations of proteins. There are two common forms of pressure-dependent potentials of mean force (PMFs) derived from hydrophobic molecules available for coarse-grained molecular simulations of protein folding and unfolding under hydrostatic pressure. Although both PMFs include a desolvation barrier separating the direct contact well and the solvent-mediated contact well, how these features vary with hydrostatic pressure is still debated. There is a need for a systematic comparison of these two PMFs on a protein. We investigated the two different pressure-dependencies on the desolvation potential in a structure-based protein model using coarse-grained molecular simulations. We compared the simulation results to the known behavior of proteins based on experimental evidence. We showed that the protein’s folding transition curve on the pressure–temperature phase diagram depends on the relationship between the potential well minima and pressure. For a protein that reduces its total volume under pressure, the PMF needs to carry the feature that the direct contact well is less stable than the water-mediated contact well at high pressure. We also comment on the practicality and importance of structure-based minimalist models for understanding the phenomenological behavior of proteins under a wide range of phase space.