The opposing effect of urea and high pressure on the conformation of the protein β-hairpin: A molecular dynamics simulation study

It is a well-known fact that both concentrated aqueous urea solution (at ambient pressure) and high hydrostatic pressure, separately, cause the denaturation of proteins. But a combined effect of them i.e. the effect of high pressure on the protein conformation in concentrated aqueous urea solution is mostly unexplored except for one recent experimental study (see de Oliveira and Silva, 2015), which reported the counteracting ability of aqueous urea solution against pressure-induced denaturation of proteins. Thus, though urea causes denaturation of a protein at ambient pressure condition, remarkably, it protects protein's native conformation at high pressure. And, in the present article, the molecular insights into these rather unusual behaviors of urea molecules, at high hydrostatic pressure, towards the conformational stability of the protein beta-hairpin are examined by employing classical molecular dynamics simulation. We notice that urea-protein-backbone interaction becomes less favorable as pressure is increased. Moreover, at high pressure, the presence of urea molecules makes water-protein interactions significantly less favorable when compared to that for low pressure. Thus, these findings lead us to propose that in binary urea solution, at high pressure, the retention of the protein's native conformation arises mainly due to (a) less exposure of protein-backbone for urea molecules and (b) significantly less favorable water-protein interactions. (C) 2017 Elsevier B.V. All rights reserved.