National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, 15 Datun Road, Chaoyang District, Beijing 100101, China.
Protein Eng Des Sel. 2011 Jan;24(1-2):69-78. doi: 10.1093/protein/gzq100. Epub 2010 Nov 12.
Prions are proteins that can undergo a heritable conformational change to an aggregated amyloid-like state, which is then transmitted to other similar molecules. Ure2, the nitrogen metabolism regulation factor of Saccharomyces cerevisiae, shows prion properties in vivo and forms amyloid fibrils in vitro. Ure2 consists of an N-terminal prion-inducing domain and a C-terminal functional domain. Previous studies have shown that mutations affecting the prion properties of Ure2 are not restricted to the N-terminal prion domain: the deletion of residues 151-158 in the C-domain increases the in vivo prion-inducing propensity of Ure2. Here, we characterized this mutant in vitro and found that the 151-158 deletion has minimal effect on the thermodynamic stability or folding properties of the protein. However, deletion of residues 151-158 accelerates the nucleation, growth and fragmentation of amyloid-like aggregates in vitro, and the aggregates formed are able to seed formation of fibrils of the wild-type protein. In addition, the absence of 151-158 was found to disrupt the inhibitory effect of the Hsp40 chaperone Ydj1 on Ure2 fibril formation. These results suggest that the enhanced in vivo prion-inducing ability of the 151-158 deletion mutant is due to its enhanced ability to generate prion seeds.
朊病毒是一种可以发生遗传构象改变并聚集成淀粉样纤维的蛋白质，这种改变随后会传递给其他类似的分子。酿酒酵母的氮代谢调节因子 Ure2 在体内表现出朊病毒特性，并在体外形成淀粉样纤维。Ure2 由一个 N 端朊病毒诱导结构域和一个 C 端功能结构域组成。先前的研究表明，影响 Ure2 朊病毒特性的突变不仅限于 N 端朊病毒结构域：C 结构域中 151-158 个残基的缺失会增加 Ure2 在体内诱导朊病毒的倾向。在这里，我们对这种突变体进行了体外特征描述，发现 151-158 缺失对蛋白质的热力学稳定性或折叠特性几乎没有影响。然而，151-158 个残基的缺失会加速淀粉样样聚集物的成核、生长和碎片化，并且形成的聚集物能够引发野生型蛋白质的纤维形成。此外，发现缺失 151-158 会破坏 Hsp40 伴侣 Ydj1 对 Ure2 纤维形成的抑制作用。这些结果表明，151-158 缺失突变体在体内增强的诱导朊病毒能力是由于其增强了产生朊病毒种子的能力。
