Ure2p protein

Chan,J. C., Oyler, N. A., Yau, W. M., and Tycko, R. (2005). Parallel beta-sheets and polar zippers in amyloid fibrils formed by residues 10-39 of the yeast prion protein Ure2p. Biochemistry 44, 10669-10680. 

All fungal prion proteins have a so-called prion domain and a functional domain. The prion domain is a region of the polypeptide chain that is necessary and sufficient for prion formation and maintenance (Fig. 1 Wickner et al., 2002). For Ure2p and Sup35p, the functional domain is responsible for the cellular activity of the normal form of the protein. 

The prion domains of Ure2p, Sup35p, and Rnqlp have unusual amino acid compositions, with abnormally high contents of the polar uncharged residues, Asn and Gin, and relatively low contents of charged and hydrophobic amino acids. In contrast, the amino acid composition of the HET-s prion domain is more typical of a normal globular protein. 

As with Ure2p, expression of a Sup35p variant lacking the prion domain restores the translation termination activity of the full-length protein in... 

Fig. 3. Structures of prion protein globular domains. (A) Crystal structure of the C-terminal domain dimer of Ure2p (pdb file 1HQO). (B) NMR structure of the C-terminal domain monomer of PrP (pdb file 1E1G).

All fungal prion proteins readily form filaments in vitro (Dos Reis et al., 2002 Glover et al., 1997 Sondheimer and Lindquist, 2000 Taylor et al., 1999). In near-native buffer conditions, filament formation typically occurs in hours to days. Ure2p filaments assembled in vitro have a diameter of —20 nm and like the filaments observed in situ (Section III.A Fig. 4), they are not hollow. 

Chimeras in which the prion domains of Ure2p and Sup35p are fused with other unrelated proteins also form filaments (Baxa et al., 2002 Diaz-Avalos et al., 2005 King and Diaz-Avalos, 2004 Schlumpberger et al, 2000)... 

The observations summarized in Section III.A and III.B suggests that the filaments detected in vivo are, in fact, the prion and that the filaments assembled in vitro from purified protein are the same as or closely related to the in vivo material. To substantiate this proposition, it is important to show that filaments formed in vitro are, in fact, infectious. Such infectivity has now been demonstrated for HET-s (Maddelein et al, 2002), Sup35p (King and Diaz-Avalos, 2004 Tanaka et al., 2004), and Ure2p (Fig. 6 Brachmann etal., 2005). In vitro -assembled filaments were brought into cells by biolistic... 

In consideration of thermal stability, a calorimetric investigation of Ure2p prion domain-containing filaments detected no evidence of these domains denaturing up to 105°C (Baxa et al., 2004). In comparison, most proteins denature at temperatures of 50—70°C and rarely exceed 80—90°C, except for proteins of extreme thermophiles. 

Bousset, L., Thomson, N. H., Radford, S. E., and Melki, R. (2002). The yeast prion Ure2p retains its native a-helical conformation upon assembly into protein fibrils in vitro. EMBOJ. 21, 2903-2911. 

Edskes, H. K., and Wickner, R. B. (2002). Conservation of a portion of the S. cerevisiae Ure2p prion domain that interacts with the full-length protein. Proc. Natl. Acad. Sci. USA 99(Suppl. 4), 16384-16391. 

Fay, N., Inoue, Y., Bousset, L., Taguchi, H., and Melki, R. (2003). Assembly of the yeast prion Ure2p into protein fibrils. Thermodynamic and kinetic characterization. /. Biol. Chem. 278, 30199-30205. 

Schlumpberger, M., Wille, H., Baldwin, M. A., Buder, D. A., Herskowitz, I., and Prusiner, S. B. (2000). The prion domain of yeast Ure2p induces autocatalytic formation of amyloid fibers by a recombinant fusion protein. Protein Sci. 9, 440-451. 

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