Amyloid formation characteristics of GNNQQNY from yeast prionprotein Sup35
and its seeding with heterogeneous polypeptides
ABSTRACT
Sup35 is a prion-like protein from yeast and shares the ability to transmit
its aberrant fold and to aggregateinto amyloid fibrils.7GNNQQNY13from the prion-determining domain of Sup35 was reported to forman amyloid.
We first investigated the self-aggregation transition behavior of GNNQQNY
to the β-sheetamyloid state under various conditions. Mechanical stirring
using a magnetic bar resulted in acceleratedaggregation of the GNNQQNY.
The aggregation rate of GNNQQNY was also dependent on its concentra-tion;
the higher the GNNQQNY concentration, the faster the aggregation. Circular
dichroism and Fouriertransform-infrared spectral data indicated the formation
of the β-sheet structure in the GNNQQNY aggre-gates. The fluorescence experiments
using an amyloid-specific thioflavin T also demonstrated that theGNNQQNY
aggregates formed the amyloid structures. The amyloid structure of the
GNNQQNY aggre-gates served as seeds for the elongation of the monomeric
GNNQQNY in the solution state. We furtherstudied the ability of the GNNQQNY
amyloid fibrils to act as seeds for the elongation of the amyloid-forming
monomeric proteins (albumin, lysozyme and insulin). The cross-seeding experiments
suggestedthat the GNNQQNY aggregate could possibly promote the amyloid
fibril formation of heterogeneousinsulin. The inverse monomeric GNNQQNY
would have a binding capacity for the heterogeneous already-formed amyloid-β
fibrils on a mice brain section. These basic data could be informative
for elucidatingthe pathogenic and/or propagation mechanisms of prion agents
and developing effective therapeuticsand/or diagnosis for prion diseases.