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Influence of the N‐terminal domain on the aggregation properties of the prion protein
Author(s) -
Frankenfield Kristen N.,
Powers Evan T.,
Kelly Jeffery W.
Publication year - 2005
Publication title -
protein science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.353
H-Index - 175
eISSN - 1469-896X
pISSN - 0961-8368
DOI - 10.1110/ps.051434005
Subject(s) - protein aggregation , prion protein , c terminus , biophysics , chemistry , in vitro , n terminus , nucleation , plasma protein binding , protein folding , microbiology and biotechnology , biochemistry , biology , peptide sequence , amino acid , medicine , disease , pathology , gene , organic chemistry
Prion diseases appear to be caused by the aggregation of the cellular prion protein (PrP C ) into an infectious form denoted PrP Sc . The in vitro aggregation of the prion protein has been extensively investigated, yet many of these studies utilize truncated polypeptides. Because the C‐terminal portion of PrP Sc is protease‐resistant and retains infectivity, it is assumed that studies on this fragment are most relevant. The full‐length protein can be distinguished from the truncated protein because it contains a largely structured, α‐helical, C‐terminal region in addition to an N terminus that is unstructured in the absence of metal ion binding. Herein, the in vitro aggregation of a truncated portion of the prion protein (PrP 90–231) and a full‐length version (PrP 23–231) were compared. In each case, concentration‐dependent aggregation was analyzed to discern whether it proceeds by a nucleation‐dependent pathway. Both protein constructs appear to aggregate via a nucleated polymerization with a small nucleus size, yet the later steps differ. The full‐length protein forms larger aggregates than the truncated protein, indicating that the N terminus may mediate higher‐order aggregation processes. In addition, the N terminus has an influence on the assembly state of PrP before aggregation begins, causing the full‐length protein to adopt several oligomeric forms in a neutral pH buffer. Our results emphasize the importance of studying the full‐length protein in addition to the truncated forms for in vitro aggregation studies in order to make valid hypotheses about the mechanisms of prion aggregation and the distribution of aggregates in vivo.