Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720-3202, USA; HALOmem, University of Halle, Kurt-Mothes-Str. 3, 06120 Halle, Germany.
Sci Rep. 2011;1:17. doi: 10.1038/srep00017. Epub 2011 Jun 17.
COPII-coated vesicles form at the endoplasmic reticulum for cargo transport to the Golgi apparatus. We used in vitro reconstitution to examine the roles of the COPII scaffold in remodeling the shape of a lipid bilayer. Giant Unilamellar Vesicles were examined using fast confocal fluorescence and cryo-electron microscopy in order to avoid separation steps and minimize mechanical manipulation. COPII showed a preference for high curvature structures, but also sufficient flexibility for binding to low curvatures. The COPII proteins induced beads-on-a-string-like constricted tubules, similar to those previously observed in cells. We speculate about a mechanical pathway for vesicle fission from these multibudded COPII-coated tubules, considering the possibility that withdrawal of the Sar1 amphipathic helix upon GTP hydrolysis leads to lipid bilayer destabilization resulting in fission.
COPII 被膜小泡在内质网上形成，用于将货物运输到高尔基体。我们使用体外重组来研究 COPII 支架在重塑脂质双层形状方面的作用。使用快速共聚焦荧光和冷冻电子显微镜检查巨单层囊泡，以避免分离步骤并尽量减少机械操作。COPII 优先与高曲率结构结合，但也具有足够的灵活性与低曲率结构结合。COPII 蛋白诱导类似串珠状的收缩小管，类似于先前在细胞中观察到的那些。考虑到 Sar1 两亲螺旋在 GTP 水解后缩回导致脂质双层不稳定从而导致分裂的可能性，我们推测从这些多芽 COPII 包被的小管中分离囊泡的一种机械途径。
