Department of Biological Sciences, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA.
J Biol Chem. 2011 Jun 10;286(23):20125-9. doi: 10.1074/jbc.C111.245324. Epub 2011 Apr 22.
Biogenesis of the ribbon-like membrane network of the mammalian Golgi requires membrane tethering by the conserved GRASP domain in GRASP65 and GRASP55, yet the tethering mechanism is not fully understood. Here, we report the crystal structure of the GRASP55 GRASP domain, which revealed an unusual arrangement of two tandem PDZ folds that more closely resemble prokaryotic PDZ domains. Biochemical and functional data indicated that the interaction between the ligand-binding pocket of PDZ1 and an internal ligand on PDZ2 mediates the GRASP self-interaction, and structural analyses suggest that this occurs via a unique mode of internal PDZ ligand recognition. Our data uncover the structural basis for ligand specificity and provide insight into the mechanism of GRASP-dependent membrane tethering of analogous Golgi cisternae.
哺乳动物高尔基体带状膜网络的生物发生需要 GRASP65 和 GRASP55 中的保守 GRASP 结构域来进行膜连接，但这种连接机制尚未完全阐明。在这里，我们报告了 GRASP55GRASP 结构域的晶体结构，该结构揭示了两个串联 PDZ 折叠的异常排列，其更类似于原核 PDZ 结构域。生化和功能数据表明，PDZ1 的配体结合口袋与 PDZ2 上的内部配体之间的相互作用介导了 GRASP 自身相互作用，结构分析表明这是通过一种独特的内部 PDZ 配体识别模式发生的。我们的数据揭示了配体特异性的结构基础，并为 GRASP 依赖的类似高尔基体潴泡膜连接的机制提供了深入了解。
