Zhao Jianfeng, Li Bowen, Huang Xiaochen, Morelli Xavier, Shi Ning
From the State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou 350002, China and.
the Centre de Recherche en Cancérologie de Marseille (CRCM), INSERM, CNRS, Aix-Marseille Université, Institut Paoli-Calmettes, 13009 Marseille, France.
J Biol Chem. 2017 Feb 17;292(7):2956-2965. doi: 10.1074/jbc.M116.765990. Epub 2017 Jan 3.
Golgin45 is required for normal Golgi structure and the transportation of protein from the ER. It forms a specific complex with GRASP55 Little is known regarding the molecular details of this interaction and its structural role in stacking of the Golgi complex. Here, we present the crystal structure of the GRASP domains of GRASP55 in complex with the Golgin45 C-terminal peptide, determined at 1.33 Å resolution. Similar to the structure of GRASP65 bound to GM130 reported recently, this structure reveals more than one interacting site and involves both PDZ1 and PDZ2 domains of the GRASP simultaneously. The C-terminal peptides of Golgin45 and GM130 present a conserved PDZ domain binding motif sequence and recognize the canonical PDZ-peptide binding groove of the PDZ1 domains of GRASP55 and GRASP65. A main difference in this recognition process resides in a structural rearrangement of GRASP65-GM130 that does not occur for the GRASP55-Golgin45 complex. The binding site at the cleft between the PDZ1 and PDZ2 domains of GRASP65 is dominated by hydrophobic interactions with GM130 that are not observed in the GRASP55-Golgin45 complex. In addition, a unique zinc finger structure is revealed in the GRASP55-Golgin45 complex crystal structure. Mutagenesis experiments support these structural observations and demonstrate that two of these sites are required to form a stable complex. Finally, a novel Golgi stacking model is proposed according to these structural findings.
高尔基体蛋白45（Golgin45）对于正常的高尔基体结构以及蛋白质从内质网的运输是必需的。它与GRASP55形成一种特定的复合物。关于这种相互作用的分子细节及其在高尔基体复合物堆叠中的结构作用，人们了解甚少。在这里，我们展示了GRASP55的GRASP结构域与高尔基体蛋白45 C末端肽复合物的晶体结构，分辨率为1.33 Å。与最近报道的GRASP65与GM130结合的结构相似，该结构揭示了不止一个相互作用位点，并且同时涉及GRASP的PDZ1和PDZ2结构域。高尔基体蛋白45和GM130的C末端肽呈现出保守的PDZ结构域结合基序序列，并识别GRASP55和GRASP65的PDZ1结构域的典型PDZ - 肽结合凹槽。这种识别过程的一个主要差异在于GRASP65 - GM130发生了结构重排，而GRASP55 - 高尔基体蛋白45复合物没有。GRASP65的PDZ1和PDZ2结构域之间裂隙处的结合位点主要由与GM130的疏水相互作用主导，而在GRASP55 - 高尔基体蛋白45复合物中未观察到这种相互作用。此外，在GRASP55 - 高尔基体蛋白45复合物晶体结构中揭示了一种独特的锌指结构。诱变实验支持了这些结构观察结果，并表明形成稳定复合物需要其中两个位点。最后，根据这些结构发现提出了一种新的高尔基体堆叠模型。
