The molecular organization of the fungal prion HET-s in its amyloid form.
The prion hypothesis states that it is solely the three-dimensional structure of the polypeptide chain that distinguishes the prion and nonprion forms of the protein. For HET-s, the atomic-resolution structure of the isolated prion domain HET-s(218-289), consisting of a highly ordered triangular cross-beta arrangement, is known. Here we present a solid-state NMR study of fibrils of the full-length HET-s prion in which we compare their spectra with spectra from isolated C-terminal prion domain fibrils and the crystalline N-terminal globular domain HET-s(1-227). The spectra reveal unequivocally that the highly ordered structure of the isolated prion domain HET-s(218-289) is conserved in the context of the full-length fibrils investigated here. However, the globular domain loses much of its tertiary structure while partly retaining its secondary structure, thus exhibiting behavior reminiscent of a molten globule. Flexible residues that may constitute the linker connecting the two domains are detected using INEPT (insensitive nuclei enhanced by polarization transfer) spectroscopy. Based on our data, we propose a structural model that is in line with a general model developed for amyloid fibrils built from a cross-beta core decorated with globular domains. The loss of structure in the HET-s globular domain sharply contrasts with the behavior observed for fibrils of Ure2p and suggests that there is considerable structural diversity in the fibrils of globular-domain-containing prions despite their similar appearances at the microscopic level.
Wasmer
Christian
C
Physical Chemistry, ETH Zürich, Wolfgang-Pauli-Strasse 10, CH-8093 Zurich, Switzerland.
Schütz
Anne
A
Loquet
Antoine
A
Buhtz
Carolin
C
Greenwald
Jason
J
Riek
Roland
R
Böckmann
Anja
A
Meier
Beat H
BH
D000682:Amyloid / Q000737:chemistry*; D017124:Conserved Sequence; D057927:Hydrophobic and Hydrophilic Interactions; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D011328:Prions / Q000737:chemistry*; D017434:Protein Structure, Tertiary; D012441:Saccharomyces cerevisiae / Q000737:chemistry*; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry*
D000682:Amyloid; D011328:Prions; D029701:Saccharomyces cerevisiae Proteins