Silva R A Gangani D, Barber-Armstrong Wendy, Decatur Sean M
Department of Chemistry, Mount Holyoke College, South Hadley, Massachusetts 01075, USA.
J Am Chem Soc. 2003 Nov 12;125(45):13674-5. doi: 10.1021/ja036725v.
Insight into the details of protein misfolding diseases requires a detailed understanding of the conformation and dynamics of multistrand beta-sheet aggregates. Here, we report an isotope-edited FTIR study of a model peptide directed at the elucidation of residue-level details of the structure and mechanism of a beta-sheet aggregate. A series of specifically isotope-labeled derivatives of a short peptide (H1) derived from residues 109 through 122 of the prion protein PrPC have been synthesized and characterized by FTIR. On the basis of the analysis of variable temperature FTIR spectra of these peptides in solution, the organization of strands within the beta-sheets has been determined; at equilibrium, the strands form a beta-sheet in which the hydrophobic core (112-122) participates in the sheet structure, resulting in the alignment of residue 117 in all of the strands. The peptides initially form a kinetically trapped intermediate beta-sheet, with a distribution of strand alignments, which can be rearranged into the stable equilibrium conformation by an annealing cycle. These observations are discussed in terms of the biological significance of residue 117 of the prion protein and the mechanism of beta-aggregate nucleation in prion proteins.
深入了解蛋白质错误折叠疾病的细节需要详细了解多链β-折叠聚集体的构象和动力学。在此，我们报告了一项同位素编辑的傅里叶变换红外光谱（FTIR）研究，该研究针对一种模型肽，旨在阐明β-折叠聚集体结构和机制的残基水平细节。我们合成了一系列从朊病毒蛋白PrPC的109至122位残基衍生而来的短肽（H1）的特异性同位素标记衍生物，并通过FTIR对其进行了表征。基于对这些肽在溶液中的变温FTIR光谱分析，确定了β-折叠内链的组织方式；在平衡状态下，这些链形成一个β-折叠，其中疏水核心（112 - 122）参与折叠结构，导致所有链中117位残基的排列。这些肽最初形成一种动力学捕获的中间β-折叠，具有链排列的分布，通过退火循环可将其重排为稳定的平衡构象。我们根据朊病毒蛋白117位残基的生物学意义以及朊病毒蛋白中β-聚集体成核机制对这些观察结果进行了讨论。
