Laboratory of Molecular Biophysics, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland 20892, USA.
J Phys Chem B. 2010 Apr 8;114(13):4615-22. doi: 10.1021/jp908092e.
Understanding how environmental factors affect the conformational dynamics of alpha-synuclein (alpha-syn) is of great importance because the accumulation and deposit of aggregated alpha-syn in the brain are intimately connected to Parkinson's disease etiology. Measurements of steady-state and time-resolved fluorescence of single tryptophan-containing alpha-syn variants have revealed distinct phospholipid vesicle and micelle interactions at residues 4, 39, 94, and 125. Our circular dichroism data confirm that Trp mutations do not affect alpha-syn membrane binding properties (apparent association constant K(a)app approximately 1 x 10(7) M(-1) for all synucleins) saturating at an estimated lipid-to-protein molar ratio of 380 or approximately 120 proteins covering approximately 7% of the surface area of an 80 nm diameter vesicle. Fluorophores at positions 4 and 94 are the most sensitive to the lipid bilayer with pronounced spectral blue-shifts (W4: Delta(lambda)max approximately 23 nm; W94: Delta(lambda)max approximately 10 nm) and quantum yield increases (W4, W94: approximately 3 fold), while W39 and W125 remain primarily water-exposed. Time-resolved fluorescence data show that all sites (except W125) have subpopulations that interact with the membrane.
了解环境因素如何影响α-突触核蛋白（α-syn）的构象动力学非常重要，因为脑内聚集的α-syn 的积累和沉积与帕金森病的病因密切相关。对含有单个色氨酸的α-syn 变体的稳态和时间分辨荧光的测量揭示了在残基 4、39、94 和 125 处存在明显的磷脂囊泡和胶束相互作用。我们的圆二色性数据证实，色氨酸突变不会影响 α-syn 与膜的结合特性（对于所有突触核蛋白，表观缔合常数 K(a)app 约为 1 x 10(7) M(-1)），在估计的脂质与蛋白质摩尔比为 380 时达到饱和，或者大约有 120 个蛋白质覆盖 80nm 直径囊泡表面面积的约 7%。位于位置 4 和 94 的荧光团对脂质双层最敏感，表现出明显的光谱蓝移（W4：Delta(lambda)max 约为 23nm；W94：Delta(lambda)max 约为 10nm）和量子产率增加（W4，W94：约 3 倍），而 W39 和 W125 仍然主要暴露于水中。时间分辨荧光数据表明，所有位点（除了 W125）都有与膜相互作用的亚群。
