Department of Biochemistry, University of Toronto, Toronto, ON, Canada.
Prion. 2012 Jul 1;6(3):234-9. doi: 10.4161/pri.19913.
Most prions in yeast form amyloid fibrils that must be severed by the protein disaggregase Hsp104 to be propagated and transmitted efficiently to newly formed buds. Only one yeast prion, [PSI (+) ], is cured by Hsp104 overexpression. We investigated the interaction between Hsp104 and Sup35, the priongenic protein in yeast that forms the [PSI (+) ] prion.1 We found that a 20-amino acid segment within the highly-charged, unstructured middle domain of Sup35 contributes to the physical interaction between the middle domain and Hsp104. When this segment was deleted from Sup35, the efficiency of [PSI (+) ] severing was substantially reduced, resulting in larger Sup35 particles and weakening of the [PSI (+) ] phenotype. Furthermore, [PSI (+) ] in these cells was completely resistant to Hsp104 curing. The affinity of Hsp104 was considerably weaker than that of model Hsp104-binding proteins and peptides, implying that Sup35 prions are not ideal substrates for Hsp104-mediated remodeling. In light of this finding, we present a modified model of Hsp104-mediated [PSI (+) ] propagation and curing that requires only partial remodeling of Sup35 assembled into amyloid fibrils.
酵母中的大多数朊病毒形成淀粉样纤维，必须被蛋白解聚酶 Hsp104 切断，才能有效地进行繁殖，并有效地传递到新形成的芽体中。只有一种酵母朊病毒 [PSI (+)] 可以通过 Hsp104 的过度表达来治愈。我们研究了 Hsp104 与 Sup35 之间的相互作用，Sup35 是酵母中的朊病毒蛋白，形成 [PSI (+)] 朊病毒。我们发现 Sup35 中高度荷电、无结构的中间结构域内的 20 个氨基酸片段有助于中间结构域与 Hsp104 之间的物理相互作用。当从 Sup35 中删除这个片段时，[PSI (+)] 的切断效率大大降低，导致更大的 Sup35 颗粒和 [PSI (+)] 表型减弱。此外，这些细胞中的 [PSI (+)] 完全抵抗 Hsp104 的治愈。Hsp104 的亲和力明显弱于模型 Hsp104 结合蛋白和肽的亲和力，这意味着 Sup35 朊病毒不是 Hsp104 介导的重塑的理想底物。鉴于这一发现，我们提出了一个改良的 Hsp104 介导的 [PSI (+)] 传播和治愈模型，该模型仅需要对组装成淀粉样纤维的 Sup35 进行部分重塑。
