Prion Protein Amyloid Formation under Native-like Conditions Involves Refolding of the C-terminal α-Helical Domain
Transmissible spongiform encephalopathies are associated with conformational conversion of the cellular prion protein, PrP C , into a proteinase K-resistant, amyloid-like aggregate, PrP Sc . Although the structure of PrP Sc remains enigmatic, recent studies have afforded increasingly detailed charac...
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Published in | The Journal of biological chemistry Vol. 283; no. 50; p. 34704 |
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Main Authors | , , |
Format | Journal Article |
Language | English |
Published |
American Society for Biochemistry and Molecular Biology
12.12.2008
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Online Access | Get full text |
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Summary: | Transmissible spongiform encephalopathies are associated with conformational conversion of the cellular prion protein, PrP C , into a proteinase K-resistant, amyloid-like aggregate, PrP Sc . Although the structure of PrP Sc remains enigmatic, recent studies have afforded increasingly detailed characterization of recombinant PrP amyloid. However,
all previous studies were performed using amyloid fibrils formed in the presence of denaturing agents that significantly alter
the folding state(s) of the precursor monomer. Here we report that PrP amyloid can also be generated under physiologically
relevant conditions, where the monomeric protein is natively folded. Remarkably, site-directed spin labeling studies reveal
that these fibrils possess a β-core structure nearly indistinguishable from that of amyloid grown under denaturing conditions,
where the C-terminal α-helical domain of the PrP monomer undergoes major refolding to a parallel and in-register β-structure
upon conversion. The structural similarity of fibrils formed under drastically different conditions strongly suggests that
the common β-sheet architecture within the â¼160â220 core region represents a distinct global minimum in the PrP conversion
free energy landscape. We also show that the N-terminal region of fibrillar PrP displays conformational plasticity, undergoing
a reversible structural transition with an apparent p K a of â¼5.3. The C-terminal region, on the other hand, retains its β-structure over the pH range 1â11, whereas more alkaline
buffer conditions denature the fibrils into constituent PrP monomers. This profile of pH-dependent stability is reminiscent
of the behavior of brain-derived PrP Sc , suggesting a substantial degree of structural similarity within the β-core region of these PrP aggregates. |
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ISSN: | 0021-9258 1083-351X |
DOI: | 10.1074/jbc.M806701200 |