Conformational variations in an infectious protein determine prion strain differences.
A remarkable feature of prion biology is the strain phenomenon wherein prion particles apparently composed of the same protein lead to phenotypically distinct transmissible states. To reconcile the existence of strains with the 'protein-only' hypothesis of prion transmission, it has been proposed that a single protein can misfold into multiple distinct infectious forms, one for each different strain. Several studies have found correlations between strain phenotypes and conformations of prion particles; however, whether such differences cause or are simply a secondary manifestation of prion strains remains unclear, largely due to the difficulty of creating infectious material from pure protein. Here we report a high-efficiency protocol for infecting yeast with the [PSI+] prion using amyloids composed of a recombinant Sup35 fragment (Sup-NM). Using thermal stability and electron paramagnetic resonance spectroscopy, we demonstrate that Sup-NM amyloids formed at different temperatures adopt distinct, stably propagating conformations. Infection of yeast with these different amyloid conformations leads to different [PSI+] strains. These results establish that Sup-NM adopts an infectious conformation before entering the cell--fulfilling a key prediction of the prion hypothesis--and directly demonstrate that differences in the conformation of the infectious protein determine prion strain variation.
Tanaka
Motomasa
M
Howard Hughes Medical Institute, Department of Cellular and Molecular Pharmacology, University of California-San Francisco, San Francisco, California 94143, USA.
Chien
Peter
P
Naber
Nariman
N
Cooke
Roger
R
Weissman
Jonathan S
JS
D000682:Amyloid / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D004578:Electron Spin Resonance Spectroscopy; D008954:Models, Biological; D010446:Peptide Fragments / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D010454:Peptide Termination Factors; D011328:Prions / Q000737:chemistry* / Q000145:classification* / Q000235:genetics / Q000378:metabolism; D011487:Protein Conformation; D012441:Saccharomyces cerevisiae / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry* / Q000145:classification* / Q000235:genetics / Q000378:metabolism; D013045:Species Specificity; D013696:Temperature; D014170:Transformation, Genetic
D000682:Amyloid; D010446:Peptide Fragments; D010454:Peptide Termination Factors; D011328:Prions; C068068:SUP35 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins