Laboratory of Structural Biology, National Institute of Arthritis and Musculoskeletal and Skin Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA.
J Biol Chem. 2010 Jul 23;285(30):23351-8. doi: 10.1074/jbc.M110.143776. Epub 2010 May 18.
Endophilin A1 is a BAR (Bin/amphiphysin/Rvs) protein abundant in neural synapses that senses and induces membrane curvature, contributing to neck formation in presynaptic endocytic vesicles. To investigate its role in membrane remodeling, we used cryoelectron microscopy to characterize structural changes induced in lipid vesicles by exposure to endophilin. The vesicles convert rapidly to coated tubules whose morphology reflects the local concentration of endophilin. Their diameters and curvature resemble those of synaptic vesicles in situ. Three-dimensional reconstructions of quasicylindrical tubes revealed arrays of BAR dimers, flanked by densities that we equate with amphipathic helices whose folding and membrane insertion were attested by EPR. We also observed the compression of bulbous coated tubes into 70-A-wide cylindrical micelles, which appear to mimic the penultimate (hemi-fission) stage of endocytosis. Our findings suggest that the adaptability of endophilin-lipid interactions underlies dynamic changes of endocytic membranes.
内啡啉 A1 是一种 BAR（Bin/ amphiphysin/ Rvs）蛋白，在神经突触中含量丰富，它能感知并诱导膜曲率，有助于突触前内吞小泡的颈部形成。为了研究它在膜重塑中的作用，我们使用冷冻电子显微镜来描述暴露于内啡啉后脂质体中诱导的结构变化。这些囊泡迅速转化为有被小管，其形态反映了内啡啉的局部浓度。它们的直径和曲率与原位突触小泡相似。准圆柱形小管的三维重建显示出 BAR 二聚体的排列，两侧是密度，我们将其等同于具有亲脂性螺旋的密度，其折叠和插入膜由 EPR 证明。我们还观察到球形有被小管被压缩成 70-A 宽的圆柱形胶束，这似乎模拟了胞吞作用的倒数第二个（半裂变）阶段。我们的研究结果表明，内啡啉-脂质相互作用的适应性是内吞膜动态变化的基础。
