Amyloid formation characteristics of GNNQQNY from yeast prionprotein Sup35 and its seeding with heterogeneous polypeptides

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.