The N-terminal prion domain of Ure2p converts from an unfolded to a thermally resistant conformation upon filament formation.
According to the "amyloid backbone" model of Ure2p prionogenesis, the N-terminal domain of Ure2p polymerizes to form an amyloid filament backbone surrounded by the C-terminal domains. The latter domains retain their native glutathione-S-transferase (GST)-like fold but are sterically inactivated from their regulatory role in nitrogen catabolism. We have tested this model by differential scanning calorimetry of soluble and filamentous Ure2p and of soluble C-terminal domains, combined with electron microscopy. As predicted, the C-terminal domains respond to thermal perturbation identically in all three states, exhibiting a single endotherm at 76 degrees C. In contrast, no thermal signal was associated with the N-terminal domains: in the soluble state of Ure2p, because they are unfolded; in the filamentous state, because their robust amyloid conformation resists heating to 100 degrees C.
Baxa
Ulrich
U
Laboratory of Structural Biology, National Institute of Arthritis, Musculoskeletal and Skin Diseases, National Institutes of Health, Bethesda, MD 20892, USA.
Ross
Philip D
PD
Wickner
Reed B
RB
Steven
Alasdair C
AC
D002152:Calorimetry, Differential Scanning; D005979:Glutathione Peroxidase; D006358:Hot Temperature; D008855:Microscopy, Electron, Scanning; D011328:Prions / Q000737:chemistry* / Q000648:ultrastructure; D011487:Protein Conformation; D011489:Protein Denaturation; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry* / Q000648:ultrastructure
D011328:Prions; D029701:Saccharomyces cerevisiae Proteins; D005979:Glutathione Peroxidase; C067020:URE2 protein, S cerevisiae