"Highly polar environments catalyze the unfolding of
PrPC helix 1"Martin Lingenheil, Robert Denschlag, and Paul Tavan
Eur. Biophys. J. 39, 1177-1192 (2010).
The first α-helix (H1) likely plays an important role in the conversion of the cellular prion protein (PrPC) into its pathogenic isoform (PrPSc). In this conversion, H1 may either have to unfold or may represent a site of intermolecular contact. A recent molecular dynamics simulation suggested that H1 can unfold if it is detached from the protein core [Hirschberger et al. (2006), Biophys. J. 90:3908]. It has been hypothesized that the high dielectric constant εs of the bulk water environment facilitates the unfolding of H1. To check this hypothesis, we performed a number of replica exchange molecular dynamics simulations of an H1 peptide in solvents of different εs. We found that the equilibrium helix fraction in water is less than 40 % in agreement with previous experimental findings and that the helix unfolds much
faster in water than in less polar solvents. The kinetically stabilizing effect of the organic solvents is largely unspecific and correlates well with their dielectric constant εs.
BMO authors (in alphabetic order):
Structural Stability of the Cellular Prion Protein PrPC studied by MD-Simulations
Computation of structure, electrostatics, and conformational dynamics of PrPC induced by binding of Cu(II)