Yeung T, Barlowe C, Schekman R
Department of Molecular and Cell biology, Howard Hughes Medical Institute, University of California, Berkeley 94720, USA.
J Biol Chem. 1995 Dec 22;270(51):30567-70. doi: 10.1074/jbc.270.51.30567.
Formation of vesicular intermediates in protein transport between the endoplasmic reticulum and the Golgi apparatus involves a mechanism that sorts and packages two classes of molecules into transport vesicles: targeting molecules, which are required for targeting and consumption of vesicular intermediates, and cargo proteins. In order to examine the importance of cargo in this packaging reaction, we developed an in vitro assay that quantifies vesicle formation based on segregation of targeting molecules. Here we document that endoplasmic reticulum devoid of cargo proteins is competent in the formation and release of targeting molecule-containing vesicles in a fashion indistinguishable from its normal counterpart. This observation implies that packaging of cargo proteins may be uncoupled from the recruitment of targeting molecules during vesicle budding from the endoplasmic reticulum. Using the same assay, we demonstrate that the packaging of targeting molecules into vesicles is not dependent on the lumenal chaperone, BiP (Kar2p).
在内质网与高尔基体之间的蛋白质运输过程中，囊泡中间体的形成涉及一种机制，该机制将两类分子分类并包装到运输囊泡中：靶向分子，其是囊泡中间体靶向和消耗所必需的；以及货物蛋白。为了研究货物在这种包装反应中的重要性，我们开发了一种体外测定法，该方法基于靶向分子的分离来量化囊泡形成。在此我们证明，缺乏货物蛋白的内质网能够以与其正常对应物无法区分的方式形成并释放含有靶向分子的囊泡。这一观察结果表明，在内质网出芽形成囊泡的过程中，货物蛋白的包装可能与靶向分子的募集解偶联。使用相同的测定法，我们证明靶向分子包装到囊泡中不依赖于腔内伴侣蛋白BiP（Kar2p）。
