Structural insights into the cooperative remodeling of membranes by amphiphysin/BIN1.
Structural insights into the cooperative remodeling of membranes by amphiphysin/BIN1.
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DOI：
10.1038/srep15452
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发表时间：
2015-10-21
影响因子：
4.6
通讯作者：
Mizuno N
中科院分区：
文献类型：
--
作者：
Adam J;Basnet N;Mizuno N
Amphiphyrin2/BIN1 是一种新月形 N-BAR 蛋白，在肌肉 T 管中形成深度内陷的管子方面发挥着关键作用。与参与动态膜分裂过程的其他 N-BAR 蛋白相比，Amphiphyrin2/BIN1 在结构上稳定管状结构；然而，人们对稳定作用的分子机制知之甚少。使用冷冻电镜，我们研究了两性蛋白/BIN1 在膜管上的组装。我们发现 N-BAR 结构域以高度协作的方式在膜表面自组装。我们的生化测定和 3D 重建表明，N 端两亲性螺旋 H0 在管组装的启动以及通过锁定相邻的 N-BAR 结构域进一步组织 BAR 介导的聚合中发挥着重要作用。缺乏 H0 或尖端部分的突变体（也参与邻近 BAR 单元的相互作用）会导致聚合物组织的破坏，尽管仍然可以观察到管状结构。包括 SH3 结构域的两性蛋白/BIN1 的调节区域在聚合物晶格中没有任何明显的参与。我们的研究表明，H0 螺旋和 BAR 尖端对于两栖蛋白/N-BAR 高效且有组织的自组装是必需的。
Amphiphysin2/BIN1 is a crescent-shaped N-BAR protein playing a key role in forming deeply invaginated tubes in muscle T-tubules. Amphiphysin2/BIN1 structurally stabilizes tubular formations in contrast to other N-BAR proteins involved in dynamic membrane scission processes; however, the molecular mechanism of the stabilizing effect is poorly understood. Using cryo-EM, we investigated the assembly of the amphiphysin/BIN1 on a membrane tube. We found that the N-BAR domains self-assemble on the membrane surface in a highly cooperative manner. Our biochemical assays and 3D reconstructions indicate that the N-terminal amphipathic helix H0 plays an important role in the initiation of the tube assembly and further in organizing BAR-mediated polymerization by locking adjacent N-BAR domains. Mutants that lack H0 or the tip portion, which is also involved in interactions of the neighboring BAR unit, lead to a disruption of the polymer organization, even though tubulation can still be observed. The regulatory region of amphiphysin/BIN1 including an SH3 domain does not have any apparent involvement in the polymer lattice. Our study indicates that the H0 helix and the BAR tip are necessary for efficient and organized self-assembly of amphiphysin/N-BAR.