MacLea Kyle S, Paul Kacy R, Ben-Musa Zobaida, Waechter Aubrey, Shattuck Jenifer E, Gruca Margaret, Ross Eric D
Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, Colorado, USA.
Graduate Program in Cell and Molecular Biology, Colorado State University, Fort Collins, Colorado, USA.
Mol Cell Biol. 2015 Mar;35(5):899-911. doi: 10.1128/MCB.01020-14. Epub 2014 Dec 29.
Multiple yeast prions have been identified that result from the structural conversion of proteins into a self-propagating amyloid form. Amyloid-based prion activity in yeast requires a series of discrete steps. First, the prion protein must form an amyloid nucleus that can recruit and structurally convert additional soluble proteins. Subsequently, maintenance of the prion during cell division requires fragmentation of these aggregates to create new heritable propagons. For the Saccharomyces cerevisiae prion protein Sup35, these different activities are encoded by different regions of the Sup35 prion domain. An N-terminal glutamine/asparagine-rich nucleation domain is required for nucleation and fiber growth, while an adjacent oligopeptide repeat domain is largely dispensable for prion nucleation and fiber growth but is required for chaperone-dependent prion maintenance. Although prion activity of glutamine/asparagine-rich proteins is predominantly determined by amino acid composition, the nucleation and oligopeptide repeat domains of Sup35 have distinct compositional requirements. Here, we quantitatively define these compositional requirements in vivo. We show that aromatic residues strongly promote both prion formation and chaperone-dependent prion maintenance. In contrast, nonaromatic hydrophobic residues strongly promote prion formation but inhibit prion propagation. These results provide insight into why some aggregation-prone proteins are unable to propagate as prions.
已经鉴定出多种酵母朊病毒，它们是由蛋白质结构转化为自我传播的淀粉样蛋白形式产生的。酵母中基于淀粉样蛋白的朊病毒活性需要一系列离散步骤。首先，朊病毒蛋白必须形成一个淀粉样蛋白核，该核可以募集并在结构上转化其他可溶性蛋白。随后，在细胞分裂过程中朊病毒的维持需要这些聚集体的碎片化以产生新的可遗传传播子。对于酿酒酵母朊病毒蛋白Sup35，这些不同的活性由Sup35朊病毒结构域的不同区域编码。一个富含谷氨酰胺/天冬酰胺的N端成核结构域是成核和纤维生长所必需的，而相邻的寡肽重复结构域对于朊病毒成核和纤维生长在很大程度上是可有可无的，但对于伴侣蛋白依赖性朊病毒维持是必需的。尽管富含谷氨酰胺/天冬酰胺的蛋白质的朊病毒活性主要由氨基酸组成决定，但Sup35的成核和寡肽重复结构域有不同的组成要求。在这里，我们在体内定量定义了这些组成要求。我们表明，芳香族残基强烈促进朊病毒形成和伴侣蛋白依赖性朊病毒维持。相反，非芳香族疏水残基强烈促进朊病毒形成但抑制朊病毒传播。这些结果为一些易于聚集的蛋白质不能作为朊病毒传播的原因提供了见解。
