Membrane fission by protein crowding
Membrane fission by protein crowding
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DOI：
10.1073/pnas.1616199114
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发表时间：
2017-04-18
影响因子：
11.1
通讯作者：
Stachowiak, Jeanne C.
中科院分区：
文献类型：
--
作者：
Snead, Wilton T.;Hayden, Carl C.;Stachowiak, Jeanne C.
膜裂变有助于将生物过程分割成离散的、与膜结合的体积，对细胞生命至关重要。具有特殊结构特征的蛋白质，包括紧缩环、螺旋支架和疏水性膜插入，被认为是分裂的主要驱动因素。相反，我们在这里报告了一种与蛋白质结构无关的分裂机制--膜结合蛋白质之间的空间压力。特别是，拥挤的蛋白质之间的随机碰撞会产生相当大的压力，如果在相反的膜表面上不平衡，会显著增加膜的曲率，导致分裂。利用内吞蛋白Epsin1的N-末端同源结构域(Then)，我们的结果表明，无论插入的疏水性如何，膜覆盖率与分裂都是平等的。具体地说，将基于FRET的膜覆盖率测量与多个独立的膜泡化测量相结合，揭示了随着空间压力的增加，分裂变得自发。此外，当螺旋被合成的膜结合基序取代时，分裂效率仍然有效。这些数据挑战了疏水插入驱动膜分裂的观点，相反，表明插入的作用是将蛋白质强烈地锚定在膜表面，放大空间压力。与这些结论一致，即使是绿色荧光蛋白(GFP)在高覆盖率下结合到膜上也能够有效地驱动分裂。我们的结论进一步得到强化的发现是，内在无序的蛋白质，具有大的流体动力学半径，但缺乏明确的结构，以比较小的结构蛋白质更大的效力驱动分裂。
Membrane fission, which facilitates compartmentalization of biological processes into discrete, membrane-bound volumes, is essential for cellular life. Proteins with specific structural features including constricting rings, helical scaffolds, and hydrophobic membrane insertions are thought to be the primary drivers of fission. In contrast, here we report a mechanism of fission that is independent of protein structure-steric pressure among membrane-bound proteins. In particular, random collisions among crowded proteins generate substantial pressure, which if unbalanced on the opposite membrane surface can dramatically increase membrane curvature, leading to fission. Using the endocytic protein epsin1 N-terminal homology domain (ENTH), previously thought to drive fission by hydrophobic insertion, our results show that membrane coverage correlates equally with fission regardless of the hydrophobicity of insertions. Specifically, combining FRET-based measurements of membrane coverage with multiple, independent measurements of membrane vesiculation revealed that fission became spontaneous as steric pressure increased. Further, fission efficiency remained equally potent when helices were replaced by synthetic membrane-binding motifs. These data challenge the view that hydrophobic insertions drive membrane fission, suggesting instead that the role of insertions is to anchor proteins strongly to membrane surfaces, amplifying steric pressure. In line with these conclusions, even green fluorescent protein (GFP) was able to drive fission efficiently when bound to the membrane at high coverage. Our conclusions are further strengthened by the finding that intrinsically disordered proteins, which have large hydrodynamic radii yet lack a defined structure, drove fission with substantially greater potency than smaller, structured proteins.