Nucleation-dependent conformational conversion of the Y145Stop variant of human prion protein: Structural clues for prion propagation

AUTOR(ES)

Kundu, Bishwajit

FONTE

National Academy of Sciences

RESUMO

One of the most intriguing disease-related mutations in human prion protein (PrP) is the Tyr to Stop codon substitution at position 145. This mutation results in a Gerstmann–Straussler–Scheinker-like disease with extensive PrP amyloid deposits in the brain. Here, we provide evidence for a spontaneous conversion of the recombinant polypeptide corresponding to the Y145Stop variant (huPrP23–144) from a monomeric unordered state to a fibrillar form. This conversion is characterized by a protein concentration-dependent lag phase and has characteristics of a nucleation-dependent polymerization. Atomic force microscopy shows that huPrP23–144 fibrils are characterized by an apparent periodicity along the long axis, with an average period of 20 nm. Fourier-transform infrared spectra indicate that the conversion is associated with formation of β-sheet structure. However, the infrared bands for huPrP23–144 are quite different from those for a synthetic peptide PrP106–126, suggesting conformational non-equivalence of β-structures in the disease-associated Y145Stop variant and a frequently used short model peptide. To identify the region that is critical for the self-seeded assembly of huPrP23–144 amyloid, experiments were performed by using the recombinant polypeptides corresponding to prion protein fragments 23–114, 23–124, 23–134, 23–137, 23–139, and 23–141. Importantly, none of the fragments ending before residue 139 showed a propensity for conformational conversion to amyloid fibrils, indicating that residues within the 138–141 region are essential for this conversion.

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