The structural basis of yeast prion strain variants
The structural basis of yeast prion strain variants
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DOI：
10.1038/nature06108
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发表时间：
2007-09-13
期刊：
影响因子：
64.8
通讯作者：
Weissman, Jonathan S.
中科院分区：
文献类型：
--
作者：
Toyama, Brandon H.;Kelly, Mark J. S.;Weissman, Jonathan S.
在朊病毒生物学研究中出现的许多意外中，也许最意想不到的是菌株现象，即单个蛋白质可以错误折叠成结构独特的感染性状态，从而导致可区分的表型（1-3）。类似地，蛋白质在蛋白质折叠的非传染性疾病中可以采用一系列构象；有些是有毒的，有些是耐受性良好的(4)。然而，我们对朊病毒毒株的结构差异以及这些差异如何改变其生理影响的理解仍然有限。在这里，我们使用溶液核磁共振，酰胺氢/氘（H/D）交换和诱变的组合来研究酵母Sup35朊病毒的两个菌株构象之间的结构差异，称为Sc4和Sc37（参考文献5）。我们发现这两个菌株有一个重叠的淀粉样蛋白核心，覆盖了富含Gln/ asn的前40个氨基酸的大部分，高度保护了H/D交换，对突变非常敏感。这些特征表明，核是由紧密排列的β -片组成的，可能类似于sup35衍生肽的x射线晶体学显示的“立体拉链”结构（6,7）。稳定的结构在Sc37构象中被大大扩展，包含了前70个氨基酸，这揭示了为什么该菌株的纤维稳定性增加，而伴侣介导的复制能力下降(8)。我们的研究结果表明，朊病毒毒株涉及大规模的构象差异，并为理解广泛的功能研究提供了结构基础，包括构象变化如何改变朊病毒毒株的生理影响。
Among the many surprises to arise from studies of prion biology, perhaps the most unexpected is the strain phenomenon whereby a single protein can misfold into structurally distinct, infectious states that cause distinguishable phenotypes(1-3). Similarly, proteins can adopt a spectrum of conformations in non-infectious diseases of protein folding; some are toxic and others are well tolerated(4). However, our understanding of the structural differences underlying prion strains and how these differences alter their physiological impact remains limited. Here we use a combination of solution NMR, amide hydrogen/deuterium (H/D) exchange and mutagenesis to study the structural differences between two strain conformations, termed Sc4 and Sc37 (ref. 5), of the yeast Sup35 prion. We find that these two strains have an overlapping amyloid core spanning most of the Gln/Asn-rich first 40 amino acids that is highly protected from H/D exchange and very sensitive to mutation. These features indicate that the cores are composed of tightly packed beta-sheets possibly resembling 'steric zipper' structures revealed by X-ray crystallography of Sup35-derived peptides(6,7). The stable structure is greatly expanded in the Sc37 conformation to encompass the first 70 amino acids, revealing why this strain shows increased fibre stability and decreased ability to undergo chaperone-mediated replication(8). Our findings establish that prion strains involve large-scale conformational differences and provide a structural basis for understanding a broad range of functional studies, including how conformational changes alter the physiological impact of prion strains.