van der Wel Patrick C A, Lewandowski Józef R, Griffin Robert G
Francis Bitter Magnet Laboratory and Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
J Am Chem Soc. 2007 Apr 25;129(16):5117-30. doi: 10.1021/ja068633m. Epub 2007 Mar 31.
Sup35p is a prion protein found in yeast that contains a prion-forming domain characterized by a repetitive sequence rich in Gln, Asn, Tyr, and Gly amino acid residues. The peptide GNNQQNY7-13 is one of the shortest segments of this domain found to form amyloid fibrils, in a fashion similar to the protein itself. Upon dissolution in water, GNNQQNY displays a concentration-dependent polymorphism, forming monoclinic and orthorhombic crystals at low concentrations and amyloid fibrils at higher concentrations. We prepared nanocrystals of both space groups as well as fibril samples that reproducibly contain three (coexisting) structural forms and examined the specimens with magic angle spinning (MAS) solid-state nuclear magnetic resonance. 13C and 15N MAS spectra of both nanocrystals and fibrils reveal narrow resonances indicative of a high level of microscopic sample homogeneity that permitted resonance assignments of all five species. We observed variations in chemical shift among the three dominant forms of the fibrils which were indicated by the presence of three distinct, self-consistent sets of correlated NMR signals. Similarly, the monoclinic and orthorhombic crystals exhibit chemical shifts that differ from one another and from the fibrils. Collectively, the chemical shift data suggest that the peptide assumes five conformations in the crystals and fibrils that differ from one another in subtle but distinct ways. This includes variations in the mobility of the aromatic Tyr ring. The data also suggest that various structures assumed by the peptide may be correlated to the "steric zipper" observed in the monoclinic crystals.
Sup35p是一种在酵母中发现的朊病毒蛋白，它含有一个朊病毒形成结构域，其特征是富含谷氨酰胺、天冬酰胺、酪氨酸和甘氨酸氨基酸残基的重复序列。肽段GNNQQNY7 - 13是该结构域中发现的最短的能形成淀粉样纤维的片段之一，其形成方式与蛋白质本身类似。在水中溶解时，GNNQQNY呈现浓度依赖性多态性，在低浓度下形成单斜晶系和正交晶系晶体，在高浓度下形成淀粉样纤维。我们制备了两种空间群的纳米晶体以及可重复包含三种（共存）结构形式的纤维样品，并使用魔角旋转（MAS）固态核磁共振对样品进行了检测。纳米晶体和纤维的13C和15N MAS谱显示出窄共振，这表明微观样品具有高度同质性，从而能够对所有五种物质进行共振归属。我们观察到纤维的三种主要形式之间化学位移的变化，这由三组不同的、自洽的相关核磁共振信号表明。同样，单斜晶系和正交晶系晶体表现出彼此不同且与纤维不同的化学位移。总体而言，化学位移数据表明该肽在晶体和纤维中呈现出五种构象，它们彼此之间存在细微但明显的差异。这包括芳香族酪氨酸环的流动性变化。数据还表明，该肽所呈现的各种结构可能与在单斜晶系晶体中观察到的“空间拉链”相关。
