Roles of Amphipathic Helices and the Bin/Amphiphysin/Rvs (BAR) Domain of Endophilin in Membrane Curvature Generation
Roles of Amphipathic Helices and the Bin/Amphiphysin/Rvs (BAR) Domain of Endophilin in Membrane Curvature Generation
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DOI：
10.1074/jbc.m110.127811
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发表时间：
2010-06-25
影响因子：
4.8
通讯作者：
Langen, Ralf
中科院分区：
文献类型：
--
作者：
Jao, Christine C.;Hegde, Balachandra G.;Langen, Ralf
在许多重要的细胞过程中，包括内吞作用和囊泡运输，都需要控制膜曲率。内啡肽是一种bin/amphiphysin/rvs（BAR）结构域蛋白，其通过作为二聚体的膜结合促进膜曲率来诱导囊泡形成。使用定点自旋标记和EPR光谱，我们表明，大鼠内亲和素A1二聚体晶体学确定的整体BAR域结构主要是囊泡条件下保持。自旋标记的侧链上的BAR域的凹面不渗透到酰基链内部，表明BAR域的相互作用，只有外围与弯曲的双层的表面。结合EPR数据和计算细化，我们确定了残基63-86的结构，一个区域，是无序的晶体结构中的大鼠endophilin A1。在膜结合时，内亲和素二聚体的每个亚基中的残基63-75形成略微倾斜的两亲性α-螺旋，其直接与膜相互作用。在它们的主要构象中，这些螺旋与BAR结构域的长轴正交。在这种构象中，两亲性螺旋被定位成充当分子楔，其诱导膜沿BAR结构域的凹面沿着弯曲。
Control of membrane curvature is required in many important cellular processes, including endocytosis and vesicular trafficking. Endophilin is a bin/amphiphysin/rvs (BAR) domain protein that induces vesicle formation by promotion of membrane curvature through membrane binding as a dimer. Using site-directed spin labeling and EPR spectroscopy, we show that the overall BAR domain structure of the rat endophilin A1 dimer determined crystallographically is maintained under predominantly vesiculating conditions. Spin-labeled side chains on the concave surface of the BAR domain do not penetrate into the acyl chain interior, indicating that the BAR domain interacts only peripherally with the surface of a curved bilayer. Using a combination of EPR data and computational refinement, we determined the structure of residues 63-86, a region that is disordered in the crystal structure of rat endophilin A1. Upon membrane binding, residues 63-75 in each subunit of the endophilin dimer form a slightly tilted, amphipathic alpha-helix that directly interacts with the membrane. In their predominant conformation, these helices are located orthogonal to the long axis of the BAR domain. In this conformation, the amphipathic helices are positioned to act as molecular wedges that induce membrane curvature along the concave surface of the BAR domain.