Different associational and conformational behaviors between the second and third repeat fragments in the tau microtubule-binding domain.
Different associational and conformational behaviors between the second and third repeat fragments in the tau microtubule-binding domain.
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DOI：
10.1046/j.1432-1033.2003.03956.x
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发表时间：
2004-02
期刊：
影响因子：
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通讯作者：
K. Minoura;T. Yao;K. Tomoo;M. Sumida;M. Sasaki;T. Taniguchi;T. Ishida
中科院分区：
文献类型：
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作者：
K. Minoura;T. Yao;K. Tomoo;M. Sumida;M. Sasaki;T. Taniguchi;T. Ishida
水溶性tau蛋白的微管结合区中的第三个重复片段(R3)被认为在蛋白质的丝状组装中起着重要作用。为了阐明R3与第二重复序列R2的结合和构象特征，用硫代黄素荧光法和电子显微镜监测了肝素诱导的这些多肽片段的组装谱。通过CD测量监测了三氟乙醇在水溶液中诱导的从随机结构到α-螺旋结构的可逆构象变化，并通过二维1H-核磁共振测量和分子模拟计算相结合的方法分析了R2在三氟乙醇溶液中的结构，以便与R3的结构进行比较。R3的组装速度明显快于R2，尽管它们的氨基酸序列相似。R2的平均核磁共振构象具有全跨α螺旋结构。在三氟乙醇中观察到的R2和R3构象的相似特征是，Leu10-Leu20/Lys20序列具有螺旋结构，各自的侧链呈两亲性分布，而C-末端部分都是柔性的。相反，在N-末端Val1-Lys6序列上观察到显著的不同，即R2的螺旋构象和R3的延伸构象。这些构象行为可能与R2和R3之间不同的自聚集速度和种子反应有关。
The third repeat fragment (R3) in the four-repeat microtubule-binding domain of the water-soluble tau protein has been considered to play an essential role in the protein's filamentous assembly. To clarify the associational and conformational features that differentiate R3 from the second repeat, R2, the heparin-induced assembly profiles of these peptide fragments were monitored by the thioflavin fluorescence method and electron microscopy. The trifluoroethanol-induced reversible conformational change from a random structure to an alpha-helical structure, in an aqueous solution, was monitored by CD measurement, and the structure of R2 in trifluoroethanol solution was analyzed by a combination of two-dimensional 1H-NMR measurements and molecular modeling calculations to facilitate comparison with the structure of R3. The speed of R3 assembly was remarkably faster than that of R2, in spite of their similar amino acid sequences. The averaged NMR conformers of R2 exhibited the whole-spanning alpha-helical structure. Similar features observed in R2 and R3 conformers in trifluoroethanol were that the Leu10-Leu20/Lys20 sequence takes a helical structure with the amphipathic-like distribution of the respective side-chains, whereas the C-terminal moieties are both flexible. In contrast, a notable difference was observed at the N-terminal Val1-Lys6 sequence, namely, a helical conformation for R2 and an extended conformation for R3. These conformational behaviors would be associated with the different self-aggregation speeds and seeding reactions between R2 and R3.