title: The HET-s prion protein of the filamentous fungus Podospora anserina aggregates in vitro into amyloid-like fibrils.
abstract: The HET-s protein of Podospora anserina is a fungal prion. This protein behaves as an infectious cytoplasmic element that is transmitted horizontally from one strain to another. Under the prion form, the HET-s protein forms aggregates in vivo. The specificity of this prion model compared with the yeast prions resides in the fact that under the prion form HET-s causes a growth inhibition and cell death reaction when co-expressed with the HET-S protein from which it differs by 13 residues. Herein we describe the purification and initial characterization of recombinant HET-s protein expressed in Escherichia coli. The HET-s protein self-associates over time into high molecular weight aggregates. These aggregates greatly accelerate precipitation of the soluble form. HET-s aggregates appear as amyloid-like fibrils using electron microscopy. They bind Congo Red and show birefringence under polarized light. In the aggregated form, a HET-s fragment of approximately 7 kDa is resistant to proteinase K digestion. CD and FTIR analyses indicate that upon transition to the aggregated state, the HET-s protein undergoes a structural rearrangement characterized by an increase in antiparallel beta-sheet structure content. These results suggest that the [Het-s] prion element propagates in vivo as an infectious amyloid.
authors.affiliation: les Laboratoires Génétique Moléculaire des Champignons, Institut de Biochimie et de Génétique Cellulaires, UMR 5095 CNRS/Université de Bordeaux 2, 33077 Bordeaux cedex, France.
authors.forename: Suzana
authors.initials: S
authors.lastname: Dos Reis
authors.forename: Bénédicte
authors.initials: B
authors.lastname: Coulary-Salin
authors.forename: Vincent
authors.initials: V
authors.lastname: Forge
authors.forename: Ioan
authors.initials: I
authors.lastname: Lascu
authors.forename: Joël
authors.initials: J
authors.lastname: Bégueret
authors.forename: Sven J
authors.initials: SJ
authors.lastname: Saupe
mesh_terms: D000682:Amyloid / Q000737:chemistry*; D003001:Cloning, Molecular; D004926:Escherichia coli / Q000235:genetics; D005656:Fungal Proteins / Q000737:chemistry* / Q000302:isolation & purification / Q000648:ultrastructure; D008854:Microscopy, Electron; D008958:Models, Molecular; D008970:Molecular Weight; D011328:Prions / Q000737:chemistry*; D011487:Protein Conformation; D011489:Protein Denaturation; D020673:Protein Renaturation; D012441:Saccharomyces cerevisiae / Q000502:physiology; D020037:Sordariales / Q000737:chemistry*; D013055:Spectrophotometry, Infrared
chemical_list: D000682:Amyloid; D005656:Fungal Proteins; C083891:HET-S protein, Podospora anserina; D011328:Prions