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Spin Label Scanning Reveals Likely Locations of β‑Strands in the Amyloid Fibrils of the Ure2 Prion Domain
journal contribution
posted on 2020-03-11, 14:34 authored by Jingzhou Wang, Giovanna Park, Yoon Kyung Lee, Matthew Nguyen, Tiffany San Fung, Tiffany Yuwen Lin, Frederick Hsu, Zhefeng GuoIn yeast, the formation of Ure2 fibrils
underlies the prion state [URE3], in which the yeast loses the ability
to distinguish good nitrogen sources from bad ones. The Ure2 prion
domain is both necessary and sufficient for the formation of amyloid
fibrils. Understanding the structure of Ure2 fibrils is important
for understanding the propagation not only of the [URE3] prion but
also of other yeast prions whose prion domains share similar features,
such as the enrichment of asparagine and glutamine residues. Here,
we report a structural study of the amyloid fibrils formed by the
Ure2 prion domain using site-directed spin labeling and electron paramagnetic
resonance (EPR) spectroscopy. We completed a spin label scanning of
all the residue positions between 2 and 80 of the Ure2 prion domain.
The EPR data show that the Ure2 fibril core consists of residues 8–68
and adopts a parallel in-register β-sheet structure. Most of
the residues show strong spin–exchange interactions, suggesting
that there are only short turns and no long loops in the fibril core.
Based on the strength of spin–exchange interactions, we determined
the likely locations of the β-strands. EPR data also show that
the C-terminal region of the Ure2 prion domain is more disordered
than the N-terminal region. The roles of hydrophobic and charged residues
are analyzed. Overall, the structure of Ure2 fibrils appears to involve
a balance of stabilizing interactions, such as asparagine ladders,
and destabilizing interactions, such as stacking of charged residues.