The core of Ure2p prion fibrils is formed by the N-terminal segment in a parallel cross-β structure: evidence from solid-state NMR.
Intracellular fibril formation by Ure2p produces the non-Mendelian genetic element [URE3] in Saccharomyces cerevisiae, making Ure2p a prion protein. We show that solid-state NMR spectra of full-length Ure2p fibrils, seeded with infectious prions from a specific [URE3] strain and labeled with uniformly (15)N-(13)C-enriched Ile, include strong, sharp signals from Ile residues in the globular C-terminal domain (CTD) with both helical and nonhelical (13)C chemical shifts. Treatment with proteinase K eliminates these CTD signals, leaving only nonhelical signals from the Gln-rich and Asn-rich N-terminal segment, which are also observed in the solid-state NMR spectra of Ile-labeled fibrils formed by residues 1-89 of Ure2p. Thus, the N-terminal segment, or "prion domain" (PD), forms the fibril core, while CTD units are located outside the core. We additionally show that, after proteinase K treatment, Ile-labeled Ure2p fibrils formed without prion seeding exhibit a broader set of solid-state NMR signals than do prion-seeded fibrils, consistent with the idea that structural variations within the PD core account for prion strains. Measurements of (13)C-(13)C magnetic dipole-dipole couplings among (13)C-labeled Ile carbonyl sites in full-length Ure2p fibrils support an in-register parallel β-sheet structure for the PD core of Ure2p fibrils. Finally, we show that a model in which CTD units are attached rigidly to the parallel β-sheet core is consistent with steric constraints.
Pubmed ID: 21497604
- Kryndushkin DS
- Wickner RB
- Tycko R
Journal of molecular biology
June 3, 2011
- Agency: Intramural NIH HHS, Id: ZIA DK075031-02
- Glutathione Peroxidase
- Models, Molecular
- Nuclear Magnetic Resonance, Biomolecular
- Saccharomyces cerevisiae
- Saccharomyces cerevisiae Proteins
- Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization