Figure 4.

CD spectra of Ure2p prion domain fused with barnase and CA. In the top two images, the spectra of the soluble fusion proteins are compared with the spectra of the unfused enzymes. In the third image, spectra of Ure2p and its C-terminal domain Ure2p^66–354 are compared. These spectra are affected little by the presence of the prion domain although this moiety accounts for about 35% of the mass of Ure2^1–65-barnase. In the last image, the difference spectra, corresponding to the prion domain contribution, are shown, including that for the prion domain in soluble Ure2p. None of the spectra indicates a substantial content of secondary structure. The differences among them may reflect small conformational differences between the prion domain in close proximity to the respective folded domains or slight changes associated with the formation of small aggregates before filament formation, which proceeds at different rates for the respective constructs.