The mechanism of prion inhibition by HET-S.
HET-S (97% identical to HET-s) has an N-terminal globular domain that exerts a prion-inhibitory effect in cis on its own prion-forming domain (PFD) and in trans on HET-s prion propagation. We show that HET-S fails to form fibrils in vitro and that it inhibits HET-s PFD fibrillization in trans. In vivo analyses indicate that beta-structuring of the HET-S PFD is required for HET-S activity. The crystal structures of the globular domains of HET-s and HET-S are highly similar, comprising a helical fold, while NMR-based characterizations revealed no differences in the conformations of the PFDs. We conclude that prion inhibition is not encoded by structure but rather in stability and oligomerization properties: when HET-S forms a prion seed or is incorporated into a HET-s fibril via its PFD, the beta-structuring in this domain induces a change in its globular domain, generating a molecular species that is incompetent for fibril growth.
Greenwald
Jason
J
Laboratory of Physical Chemistry, ETH Zürich, Wolfgang-Pauli-Strasse 10, 8093 Zürich, Switzerland.
Buhtz
Carolin
C
Ritter
Christiane
C
Kwiatkowski
Witek
W
Choe
Senyon
S
Maddelein
Marie-Lise
ML
Ness
Frederique
F
Cescau
Sandra
S
Soragni
Alice
A
Leitz
Dominik
D
Saupe
Sven J
SJ
Riek
Roland
R
D000595:Amino Acid Sequence; D018360:Crystallography, X-Ray; D005656:Fungal Proteins / Q000737:chemistry* / Q000235:genetics; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation; D011328:Prions / Q000737:chemistry* / Q000235:genetics; D011487:Protein Conformation; D055503:Protein Multimerization; D055550:Protein Stability; D017434:Protein Structure, Tertiary; D012996:Solutions
D005656:Fungal Proteins; C083891:HET-S protein, Podospora anserina; D011328:Prions; D012996:Solutions