A High-pressure Approach to Examine Novel Prion Conformational Changes

Abstract

High pressure can fully reverse heat-induced PrP aggregation, and also restitute the original secondary protein structure (conversion from β- sheet to α-helical structure). The kinetics of this conversion were studied by a pressure jump technique. In the low-pressure range (up to 400 MPa), reversible protein unfolding took place, as reflected by changes in the UV absorbance of Tyr and Trp residues, and by binding of a hydrophobic fluorescent probe (ANS). The free energy of unfolding was however very different for heat- and pressure-induced processes, suggesting that heat and pressure induce different unfolded states. In the high-pressure range (400 to 700 MPa), thioflavin-T binding was observed, indicating the occurrence of still another conformational change. The high-pressure approach permitted thus to detect several prion protein conformational states and to study their inter-conversion.