Journal of Virology, November 2001, p. 10024-10032, Vol. 75, No. 21
0022-538X/01/$04.00+0 DOI: 10.1128/JVI.75.21.10024-10032.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
-Strand and
-Helix Secondary
Structure in Normal Prion Protein Inhibits Formation of Its
Protease-Resistant Isoform
Laboratory of Persistent Viral Diseases, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana 59840,1 and Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, California 943052
Received 24 April 2001/Accepted 19 July 2001
A fundamental event in the pathogenesis of transmissible spongiform
encephalopathies (TSE) is the conversion of a normal, proteinase
K-sensitive, host-encoded protein, PrP-sen, into its protease-resistant
isoform, PrP-res. During the formation of PrP-res, PrP-sen undergoes
conformational changes that involve an increase of
-sheet secondary
structure. While previous studies in which PrP-sen deletion mutants
were expressed in transgenic mice or scrapie-infected cell cultures
have identified regions in PrP-sen that are important in the formation
of PrP-res, the exact role of PrP-sen secondary structures in the
conformational transition of PrP-sen to PrP-res has not yet been
defined. We constructed PrP-sen mutants with deletions of the first
-strand, the second
-strand, or the first
-helix and tested
whether these mutants could be converted to PrP-res in both
scrapie-infected neuroblastoma cells (Sc+-MNB cells) and a
cell-free conversion assay. Removal of the second
-strand or the
first
-helix significantly altered both processing and the cellular
localization of PrP-sen, while deletion of the first
-strand had no
effect on these events. However, all of the mutants significantly
inhibited the formation of PrP-res in Sc+-MNB cells and had
a greatly reduced ability to form protease-resistant PrP in a cell-free
assay system. Thus, our results demonstrate that deletion of the
-strands and the first
-helix of PrP-sen can fundamentally
affect PrP-res formation and/or PrP-sen processing.
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