Research Group of Structural Dynamics of (Bio)chemical Systems, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany.
Biomacromolecules. 2012 Jun 11;13(6):1882-9. doi: 10.1021/bm300412q. Epub 2012 May 23.
The permeability barrier of nuclear pore complexes (NPCs) controls all exchange of macromolecules between the cytoplasm and the cell nucleus. It consists of phenylalanine-glycine (FG) repeat domains apparently organized as an FG hydrogel. It has previously been demonstrated that an FG hydrogel derived from the yeast nucleoporin Nsp1p reproduces the selectivity of authentic NPCs. Here we combined time-resolved optical spectroscopy and X-ray scattering techniques to characterize such a gel. The data suggest a hierarchy of structures that form during gelation at the expense of unstructured elements. On the largest scale, protein-rich domains with a correlation length of ~16.5 nm are evident. On a smaller length scale, aqueous channels with an average diameter of ~3 nm have been found, which possibly represent the physical structures accounting for the passive sieving effect of nuclear pores. The protein-rich domains contain characteristic β-structures with typical inter-β-strand and inter-β-sheet distances of 1.3 and 0.47 nm, respectively. During gelation, the formation of oligomeric associates is accompanied by the transfer of phenylalanines into a hydrophobic microenvironment, supporting the view that this process is driven by a hydrophobic collapse.
核孔复合物（NPC）的通透性屏障控制着细胞质和细胞核之间所有大分子的交换。它由苯丙氨酸-甘氨酸（FG）重复结构域组成，显然组织成 FG 水凝胶。先前已经证明，源自酵母核孔蛋白 Nsp1p 的 FG 水凝胶再现了真实 NPC 的选择性。在这里，我们结合了时间分辨光学光谱和 X 射线散射技术来表征这种凝胶。数据表明，在凝胶化过程中会形成结构层次，这会消耗无定形元素。在最大尺度上，存在具有约 16.5nm 相关长度的富含蛋白质的域。在较小的长度尺度上，发现了平均直径约为 3nm 的水通道，这可能代表了核孔的被动筛滤效应的物理结构。富含蛋白质的域包含特征性的β-结构，其典型的β-链间和β-片层间距离分别为 1.3nm 和 0.47nm。在凝胶化过程中，寡聚体的形成伴随着苯丙氨酸进入疏水环境，这支持了该过程是由疏水塌陷驱动的观点。
