Thư viện tri thức trực tuyến
Kho tài liệu với 50,000+ tài liệu học thuật
© 2023 Siêu thị PDF - Kho tài liệu học thuật hàng đầu Việt Nam

Tài liệu Báo cáo khoa học: The elusive intermediate on the folding pathway of the prion protein pptx
Nội dung xem thử
Mô tả chi tiết
The elusive intermediate on the folding pathway
of the prion protein
David C. Jenkins, Ian D. Sylvester and Teresa J. T. Pinheiro
Department of Biological Sciences, University of Warwick, UK
Prion diseases, which include Creutzfeldt–Jakob disease in humans, bovine spongiform encephalopathy in
cattle and scrapie in sheep, are associated with conversion of the normal cellular form of the prion protein
(PrPC) to an altered pathological form, generally designated as the scrapie isoform (PrPSc). Such diseases can
be sporadic, inherited or acquired by transmission.
Sporadic Creutzfeldt–Jakob disease accounts for 85%
of all cases of the disease; around 10–15% are associated with the familial cases and fewer than 5% are
transmitted [1].
Although coded for by the same gene [2,3] and
covalently identical [4], the structure and properties of
PrPC and PrPSc contrast greatly. Whereas PrPC is a
globular protein, composed primarily of an unstructured N-terminal region and a C-terminal domain
comprising three a-helices and two short b-strands
(Fig. 1) [5–8], PrPSc has a much higher proportion of
b-sheet structure [9]. Physicochemical studies have
shown that PrPC is monomeric, soluble in aqueous
buffer and sensitive to protease digestion, while, in
comparison, PrPSc has a high propensity to aggregate,
is water- and detergent-insoluble, and partially resistant to proteinases [2,10,11].
The details of prion conversion are not fully understood, but it is generally accepted that the key molecular event in sporadic and familial cases of prion
diseases involves a conformational transition of the
prion protein from its cellular state to the altered disease-associated form [12]. Thus, an understanding of
the folding and refolding mechanisms of the prion protein should provide insight into the process of prion
conversion, and represent a major step forward in our
understanding of the misfolding and aggregation of
PrP during disease.
Studies of the folding kinetics of PrP have indicated
that it may fold via an intermediate state [13–15], and
that this intermediate may, under as yet uncharacterized conditions, be recruited to form PrPSc. Results
from equilibrium folding studies have been ambiguous
on defining the presence of an intermediate in the folding of PrP. Initial studies apparently revealed a folding
intermediate rich in b-structure [16], later shown to be
off-pathway aggregated species in the folding of PrP
Keywords
denaturant unfolding; molten globule; phasediagram; prion conversion; prion diseases
Correspondence
T. J. T. Pinheiro, Department of Biological
Sciences, Gibbet Hill Road, University of
Warwick, Coventry CV4 7AL, UK
Fax: +44 2476 523 701
Tel: +44 2476 528 364
E-mail: t.pinheiro@warwick.ac.uk
(Received 14 August 2007, revised 20
December 2007, accepted 15 January 2008)
doi:10.1111/j.1742-4658.2008.06293.x
A key molecular event in prion diseases is the conversion of the cellular
conformation of the prion protein (PrPC) to an altered disease-associated
form, generally denoted as scrapie isoform (PrPSc). The molecular details
of this conformational transition are not fully understood, but it has been
suggested that an intermediate on the folding pathway of PrPC may be
recruited to form PrPSc. In order to investigate the folding pathway of PrP
we designed and expressed two mutants, each possessing a single strategically located tryptophan residue. The secondary structure and folding
properties of the mutants were examined. Using conventional analyses
of folding transition data determined by fluorescence and CD, and novel
phase-diagram analyses, we present compelling evidence for the presence of
an intermediate species on the folding pathway of PrP. The potential role
of this intermediate in prion conversion is discussed.
Abbreviations
PrP, prion protein; SHaPrP, Syrian hamster prion protein.
FEBS Journal 275 (2008) 1323–1335 ª 2008 The Authors Journal compilation ª 2008 FEBS 1323