de Groot Natalia Sánchez, Aviles Francesc X, Vendrell Josep, Ventura Salvador
Departament de Bioquímica i Biologia Molecular and Institut de Biotecnologia i de Biomedicina, Universitat Autònoma de Barcelona.
FEBS J. 2006 Feb;273(3):658-68. doi: 10.1111/j.1742-4658.2005.05102.x.
Protein misfolding and deposition underlie an increasing number of debilitating human disorders. Alzheimer's disease is pathologically characterized by the presence of numerous insoluble amyloid plaques in the brain, composed primarily of the 42 amino acid human beta-amyloid peptide (Abeta42). Disease-linked mutations in Abeta42 occur in or near a central hydrophobic cluster comprising residues 17-21. We exploited the ability of green fluorescent protein to act as a reporter of the aggregation of upstream fused Abeta42 variants to characterize the effects of a large set of single-point mutations at the central position of this hydrophobic sequence as well as substitutions linked to early onset of the disease located in or close to this region. The aggregational properties of the different protein variants clearly correlated with changes in the intrinsic physicochemical properties of the side chains at the point of mutation. Reduction in hydrophobicity and beta-sheet propensity resulted in an increase of in vivo fluorescence indicating disruption of aggregation, as confirmed by the in vitro analysis of synthetic Abeta42 variants. The results confirm the key role played by the central hydrophobic stretch on Abeta42 deposition and support the hypothesis that sequence tunes the aggregation propensities of polypeptides.
蛋白质错误折叠和沉积是越来越多使人衰弱的人类疾病的基础。阿尔茨海默病的病理特征是大脑中存在大量不溶性淀粉样斑块，主要由42个氨基酸的人类β-淀粉样肽（Abeta42）组成。与疾病相关的Abeta42突变发生在包含17-21位残基的中央疏水簇内或附近。我们利用绿色荧光蛋白作为上游融合Abeta42变体聚集的报告分子的能力，来表征该疏水序列中央位置的大量单点突变以及位于该区域内或附近与疾病早发相关的替代突变的影响。不同蛋白质变体的聚集特性与突变位点侧链内在物理化学性质的变化明显相关。疏水性和β-折叠倾向的降低导致体内荧光增加，表明聚集被破坏，这一点通过合成Abeta42变体的体外分析得到证实。结果证实了中央疏水片段在Abeta42沉积中所起的关键作用，并支持序列调节多肽聚集倾向的假说。
