We have synthesized both free and terminally-blocked peptide corresponding to the second helical region of the globular domain of normal human prion protein, which has recently gained the attention of structural biologists because of a possible role in the nucleation process and fibrillization of prion protein. The profile of the circular dichroism spectrum of the free peptide was that typical of alpha-helix, but was converted to that of beta-structure in about 16 h. Instead, below 2.1 x 10(-5) M, the spectrum of the blocked peptide exhibited a single band centered at 200 nm, unequivocally associated to random conformations, which did not evolve even after 24 h. Conformational preferences of this last peptide have been investigated as a function of temperature, using trifluoroethanol or low-concentration sodium dodecyl sulfate as alpha- or beta-structure inducers, respectively. Extrapolation of free energy data to zero concentration of structuring agent highlighted that the peptide prefers alpha-helical to beta-type organization, in spite of results from prediction algorithms. However, the free energy difference between the two forms, as obtained by a thermodynamic cycle, is subtle (roughly 5-8 kJ mol(-1) at any temperature from 280 K to 350 K), suggesting conformational ambivalence. This result supports the view that, in the prion protein, the structural behavior of the peptide is governed by the cellular microenvironment.

The human prion protein alpha2 helix: a thermodynamic study of its conformational preferences / Tizzano, B.; Palladino, P.; De Capua, A.; Marasco, Daniela; Rossi, F.; Benedetti, Ettore; Pedone, Carlo; Ragone, R.; Ruvo, M.. - In: PROTEINS. - ISSN 0887-3585. - STAMPA. - 59:1(2005), pp. 72-79.

The human prion protein alpha2 helix: a thermodynamic study of its conformational preferences

MARASCO, DANIELA;Rossi F.;BENEDETTI, ETTORE;PEDONE, CARLO;
2005

Abstract

We have synthesized both free and terminally-blocked peptide corresponding to the second helical region of the globular domain of normal human prion protein, which has recently gained the attention of structural biologists because of a possible role in the nucleation process and fibrillization of prion protein. The profile of the circular dichroism spectrum of the free peptide was that typical of alpha-helix, but was converted to that of beta-structure in about 16 h. Instead, below 2.1 x 10(-5) M, the spectrum of the blocked peptide exhibited a single band centered at 200 nm, unequivocally associated to random conformations, which did not evolve even after 24 h. Conformational preferences of this last peptide have been investigated as a function of temperature, using trifluoroethanol or low-concentration sodium dodecyl sulfate as alpha- or beta-structure inducers, respectively. Extrapolation of free energy data to zero concentration of structuring agent highlighted that the peptide prefers alpha-helical to beta-type organization, in spite of results from prediction algorithms. However, the free energy difference between the two forms, as obtained by a thermodynamic cycle, is subtle (roughly 5-8 kJ mol(-1) at any temperature from 280 K to 350 K), suggesting conformational ambivalence. This result supports the view that, in the prion protein, the structural behavior of the peptide is governed by the cellular microenvironment.
2005
The human prion protein alpha2 helix: a thermodynamic study of its conformational preferences / Tizzano, B.; Palladino, P.; De Capua, A.; Marasco, Daniela; Rossi, F.; Benedetti, Ettore; Pedone, Carlo; Ragone, R.; Ruvo, M.. - In: PROTEINS. - ISSN 0887-3585. - STAMPA. - 59:1(2005), pp. 72-79.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11588/201843
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