Figure 1.

The biological homogeneity of NM fibrils was confirmed by protein-only transformation. (a) Diagrams of wild-type Sup35. The black segments in the N-terminal region of Sup35 (N) represent oligopeptide repeats. The highly charged nature of the middle region (M) is indicated. The C-terminal region (C) functions in translation termination. (b–f) Biologically distinct prion states were induced when prion-minus cells were transformed with fluorescently labeled fibrils formed under different conditions. (b) Colonies transformed with buffer alone. (c) Colonies transformed with spontaneously assembled NM fibrils. A mixture of prion phenotypes is highlighted in the blue box. (d) Colonies after “protein-only” transformation at 4°C with NM fibrils that were seeded by lysates of yeast cells that carried a strong prion element. The uniform strong prion phenotypes are indicated by the light pink-colored colonies in the blue box. (e) Colonies after “protein-only” transformation at 37°C with NM fibrils that were seeded by lysates from cells carrying a weak prion element. The uniform weak prion phenotypes are indicated by the dark salmon-colored colonies in the blue box. (f) Quantification of transformation efficiency and specificity of distinct prion fibrils. Strong fibrils refer to the fibrils used in (d), while weak fibrils refer to the fibrils used in (e).