NMR characterizations of an amyloidogenic conformational ensemble of the PI3KSH3 domain
NMR characterizations of an amyloidogenic conformational ensemble of the PI3KSH3 domain
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DOI：
10.1110/ps.062154306
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发表时间：
2006-11-01
期刊：
影响因子：
8
通讯作者：
Lim, Kwang Hun
中科院分区：
文献类型：
--
作者：
Ahn, Hee-Chul;Le, Yen T. H.;Lim, Kwang Hun
淀粉样蛋白的形成与天然多肽向单体中间状态的结构变化及其自组装成不溶性聚集体有关。因此，淀粉样蛋白生成中间状态的特征对于理解淀粉样蛋白生成的早期阶段非常重要。在这里，我们对磷脂酰肌醇 3-激酶 (PI3K) SH3 结构域（模型肽）的酸解折叠淀粉样蛋白形成中间状态的结构和动态特性进行了 NMR 研究。在 pH 2.0（35 摄氏度）下研究的 SH3 结构域的单体淀粉样蛋白生成状态显示出显着无序，没有二级结构偏好。 N-15 NMR 弛豫实验表明，在淀粉样蛋白生成条件（pH 2.0，35 摄氏度）下观察时，未折叠的多肽在亚纳秒时间尺度上具有高度灵活性。然而，在主要位于β链以及天然折叠环中的残基中检测到更受限的运动。此外，通过顺磁弛豫增强（PRE）实验观察到灵活性降低的残基之间存在非天然长程相互作用。这些表明SH3结构域的酸展开状态通过淀粉样蛋白形成条件下动态限制残基之间的非天然长程接触而采用部分折叠构象。
Amyloid formation is associated with structural changes of native polypeptides to monomeric intermediate states and their self-assembly into insoluble aggregates. Characterizations of the amyloidogenic intermediate state are, therefore, of great importance in understanding the early stage of amyloidogenesis. Here, we present NMR investigations of the structural and dynamic properties of the acid-unfolded amyloidogenic intermediate state of the phosphatidylinositol 3-kinase (PI3K) SH3 domain-a model peptide. The monomeric amyloidogenic state of the SH3 domain studied at pH 2.0 (35 degrees C) was shown to be substantially disordered with no secondary structural preferences. N-15 NMR relaxation experiments indicated that the unfolded polypeptide is highly flexible on a subnanosecond timescale when observed under the amyloidogenic condition (pH 2.0, 35 degrees C). However, more restricted motions were detected in residues located primarily in the beta-strands as well as in a loop in the native fold. In addition, nonnative long-range interactions were observed between the residues with the reduced flexibility by paramagnetic relaxation enhancement (PRE) experiments. These indicate that the acid-unfolded state of the SH3 domain adopts a partly folded conformation through nonnative long-range contacts between the dynamically restricted residues at the amyloid-forming condition.