Ure2p protein filaments

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. 

Baxa U, Cheng N, Winkler DC, Chiu TK, Davies DR, Sharma D, Inouye H, Kirschner DA, Wickner RB, Steven AC (2005) Filaments of the Ure2p prion protein have a cross-beta core structure. J Struct Biol 150 170-179... 

The cofilament formation is a highly specific process. Dilution of Ure2p into a mixture of proteins results in only full-length Ure2p incorporation into the filaments formed. Likewise, filament formation by the AP peptide in the presence of native Ure2p does not result in incorporation of the Ure2p into the filaments formed (Taylor et al.,... 

Balbach JJ, Ishii Y, Antzutkin ON, Leapman RD, Rizzo NW, Dyda F, Reed J, Tycko R (2000) Amyloid fibril formation by A beta 16-22, a seven-residue fragment of the Alzheima- s beta-amyloid peptide, and structural characterization by solid state NMR. Biochemistry 39 13748-13759 Bamberger ME, Harris ME, McDonald DR, Husemann J, Landreth GE (2003) A cell surface receptor complex for fibrillar beta-amyloid mediates microglial activation. J Neurosci 23 2665-2674 Baskakov IV, Legname G, Baldwin MA, Prusiner SB, Cohen FE (2002) Pathway complexity of prion protein assembly into amyloid. J Biol Chem 277 21140-21148 Baxa U, Cheng N, Winkler DC, Chiu TK, Davies DR, Sharma D, Inouye H, Kirschner DA, Wickner RB, Steven AC (2005) Filaments of the Ure2p prion protein have a cross-beta core structure. J Stmet Biol 150 170-179... 

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