Béthune Julien, Kol Matthijs, Hoffmann Julia, Reckmann Inge, Brügger Britta, Wieland Felix
Biochemie-Zentrum der Universität Heidelberg, Im Neuenheimer Feld 328, D-69120 Heidelberg, Germany.
Mol Cell Biol. 2006 Nov;26(21):8011-21. doi: 10.1128/MCB.01055-06. Epub 2006 Aug 28.
In the formation of COPI vesicles, interactions take place between the coat protein coatomer and membrane proteins: either cargo proteins for retrieval to the endoplasmic reticulum (ER) or proteins that cycle between the ER and the Golgi. While the binding sites on coatomer for ER residents have been characterized, how cycling proteins bind to the COPI coat is still not clear. In order to understand at a molecular level the mechanism of uptake of such proteins, we have investigated the binding to coatomer of p24 proteins as examples of cycling proteins as well as that of ER-resident cargos. The p24 proteins required dimerization to interact with coatomer at two independent binding sites in gamma-COP. In contrast, ER-resident cargos bind to coatomer as monomers and to sites other than gamma-COP. The COPI coat therefore discriminates between p24 proteins and ER-resident proteins by differential binding involving distinct subunits.
在COPI囊泡的形成过程中，外被蛋白复合物与膜蛋白之间会发生相互作用：这些膜蛋白要么是用于回收到内质网（ER）的货物蛋白，要么是在内质网和高尔基体之间循环的蛋白。虽然外被蛋白复合物上针对内质网驻留蛋白的结合位点已得到表征，但循环蛋白如何与COPI外被结合仍不清楚。为了在分子水平上理解此类蛋白的摄取机制，我们研究了p24蛋白作为循环蛋白的示例以及内质网驻留货物与外被蛋白复合物的结合情况。p24蛋白需要二聚化才能在γ-COP的两个独立结合位点与外被蛋白复合物相互作用。相比之下，内质网驻留货物以单体形式结合到外被蛋白复合物，且结合位点不同于γ-COP。因此，COPI外被通过涉及不同亚基的差异结合来区分p24蛋白和内质网驻留蛋白。
