High-order oligomers of intrinsically disordered brain proteins BASP1 and GAP-43 preserve the structural disorder
High-order oligomers of intrinsically disordered brain proteins BASP1 and GAP-43 preserve the structural disorder
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DOI：
10.1111/febs.13692
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发表时间：
2016-04-01
期刊：
影响因子：
5.4
通讯作者：
Zakharov, Vladislav V.
中科院分区：
文献类型：
--
作者：
Forsova, Oksana S.;Zakharov, Vladislav V.
脑酸溶性蛋白1（BASP 1）和生长相关蛋白43（GAP 43）是突触前膜蛋白，参与轴突导向、神经再生和突触可塑性。据推测，它们在脂筏中螯合磷脂酰肌醇-4，5-二磷酸（PIP 2）。以前，我们已经表明，在阴离子磷脂或SDS的存在下，在亚胶束浓度的蛋白质形成大小不均匀的低聚物。BASP 1和GAP-43是本质无序蛋白（IDP）。鉴于此，我们研究了它们的低聚物的结构。利用戊二醛部分交联的寡聚体，BASP 1和GAP-43的聚集数估计分别为10-14和6-7个单体亚基。交联模式表明亚基呈环状排列。单体的圆二色性（CD）光谱的特征线圈样IDP显示无序的结构与高人口的聚脯氨酸-II构象。寡聚化伴随着一个小的CD光谱变化可归因于少量的-螺旋的形成。在螺旋构象的残基的数目估计为13 BASP 1和18 GAP-43。然而，低聚物的整体结构仍然是无序的，表明高度模糊。这是通过测量的流体动力学尺寸的低聚物，聚丙烯酰胺梯度凝胶电泳和尺寸排阻色谱法，并通过测定其敏感性蛋白水解消化证实。有证据表明，观察到的螺旋折叠发生在基本的效应结构域，这可能是通过SDS或PIP 2的阴离子分子拴在一起。我们的结论是，BASP 1和GAP-43寡聚体保留了一个主要的无序结构，这可能是非常重要的，他们的功能在PIP 2信号通路。
Brain acid-soluble protein-1 (BASP1) and growth-associated protein-43 (GAP-43) are presynaptic membrane proteins participating in axon guidance, neuroregeneration and synaptic plasticity. They are presumed to sequester phosphatidylinositol-4,5-bisphosphate (PIP2) in lipid rafts. Previously we have shown that the proteins form heterogeneously sized oligomers in the presence of anionic phospholipids or SDS at submicellar concentration. BASP1 and GAP-43 are intrinsically disordered proteins (IDPs). In light of this, we investigated the structure of their oligomers. Using partial cross-linking of the oligomers with glutaraldehyde, the aggregation numbers of BASP1 and GAP-43 were estimated as 10-14 and 6-7 monomer subunits, respectively. The cross-linking pattern indicated that the subunits are circularly arranged. The circular dichroism (CD) spectra of the monomers were characteristic of coil-like IDPs showing unordered structure with a high population of polyproline-II conformation. The oligomerization was accompanied by a minor CD spectral change attributable to formation of a small amount of -helix. The number of residues in the -helical conformation was estimated as 13 in BASP1 and 18 in GAP-43. However, the overall structure of the oligomers remained disordered, indicating a high degree of fuzziness'. This was confirmed by measuring the hydrodynamic dimensions of the oligomers using polyacrylamide gradient gel electrophoresis and size-exclusion chromatography, and by assaying their sensitivity to proteolytic digestion. There is evidence that the observed -helical folding occurs within the basic effector domains, which are presumably tethered together via anionic molecules of SDS or PIP2. We conclude that BASP1 and GAP-43 oligomers preserve a mostly disordered structure, which may be of great importance for their function in PIP2 signaling pathway.