整合素激活因子Talin蛋白棒状结构域的双螺旋束结构研究
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中国科学院生物物理研究所生物大分子国家重点实验室,中国科学院生物物理研究所生物大分子国家重点实验室,中国科学院生物物理研究所生物大分子国家重点实验室,中国科学院生物物理研究所生物大分子国家重点实验室

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国家自然科学基金资助项目(31470792, 31271491)


Structural Study on Two Tandem Helix Bundles of The ROD Domain of Talin, an Integrin Activator
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National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences,National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences,National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences,National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences

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This work was supported by a grant from The National Natural Science Foundation of China (31470792, 31271491)

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    摘要:

    Talin能够激活整合素(integrin),同时作为连接细胞骨架与跨膜受体整合素的桥梁,在细胞黏附、迁移等过程中发挥着关键的调控作用.整合素的激活反应是通过Talin-FERM结构域的F3结合整合素β亚基的胞内尾段来完成的.Talin在体内存在自抑制与活化两种状态,我们之前解析的F2F3/R9复合物结构显示,在自抑制状态下,整合素结合位点F3与其尾部片段Talin-R9(1654~1822 a.a.)结合,此时整合素不能被活化.然而,Talin作为一个270 ku的大蛋白,除了F3和R9以外的部分在Talin自身的活化过程中如何协同发挥作用,至今仍是未知的.我们分别解析了Talin R9-10(1654~1973 a.a.)、R10-11(1815~2140 a.a.)的双螺旋束晶体结构,单独的R9、R10、R11均为5-螺旋的螺旋束结构,R9-10之间通过一条长α螺旋连接,R9和R10交错排列在该螺旋的两侧,夹角约为150°;R10-11之间的柔性连接区在周围氢键网络的稳定下,使R10和R11形成了约120°的夹角.晶体结构中观察到的夹角与前人的小角散射及电镜结果相吻合.结合已有的R7-8、R11-12结构进行重叠,得到的R7-12拼接结构模型表现为伸展的长棒状,R8则凸出于长棒之外;R10-12不影响F3的结合,而R8不仅在空间上遮盖了F3的结合位点,而且可能通过电荷排斥F2F3.凝胶排阻层析实验也证实了这一点.本工作为进一步阐释Talin的自抑制机制提供了分子基础.

    Abstract:

    Talin, as the activator of integrin and the adaptor between the cytoskeleton and integrin, plays a key role in a series of processes such as cell adhesion and migration.The activation of integrin involves F3 subdomain of Talin-FERM domain binding the cytoplasmic tail of integrin β-subunit.Talin has two states: auto-inhibited and activated.We previously reported the auto-inhibition complex structure of Talin F2F3/R9, in which the integrin binding site F3 interacts with R9(1654~1822 a.a.) of Talin-ROD, such that integrin cannot be activated. However, besides F3 and R9, it remains unclear what structural or functional roles the other domains of the 270 ku Talin play in the regulation of its activation.Here we solved the crystal structures of Talin R9-R10 (1654~1973 a.a.) and R10-R11 (1815~2140 a.a.), respectively.R9, R10 and R11 are all 5-helix bundles.R9 and R10 is joined together by a long α-helix instead of a flexible loop, and the two bundles are located at the opposite sides of the long helix with an angle of about 150°.The linker between R10 and R11 is stabilized by neighboring hydrogen bonds, forming an angle of about 120° between the two bundles.These angles observed in our crystal structures are consistent with the previously reported SAXS and EM results.After superimposition of R9-10, R10-11 with previously reported structures of R7-8 and R11-12, a model of R7-12 was acquired, which adopts an elongated linear conformation, except that R8 protrudes from the ROD.According to this model, R10-12 does not intrude the interaction between F3 and R9, whereas R8 not only masks the F3 binding site of R9, but also might electrostatically hinders F2F3 approaching via its unique positively charged surface.This hypothesis was further verified by the results of size exclusion chromatography.Our work provides a new structural basis for studying the mechanism of Talin auto-inhibition.

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林霖,宋先强,叶盛,张荣光.整合素激活因子Talin蛋白棒状结构域的双螺旋束结构研究[J].生物化学与生物物理进展,2015,42(6):574-582

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历史
  • 收稿日期:2015-03-25
  • 最后修改日期:2015-05-03
  • 接受日期:2015-06-01
  • 在线发布日期: 2015-06-24
  • 出版日期: 2015-06-20