Structural Basis for the Interaction between Golgi Reassembly-stacking Protein GRASP55 and Golgin45.

Golgin45 is required for normal Golgi structure and the transportation of protein from the ER. It forms a specific complex with GRASP55 in vivo 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.

Zhao J ，Li B ，Huang X ，Morelli X ，Shi N ... -  《-》

Structural basis for the interaction between the Golgi reassembly-stacking protein GRASP65 and the Golgi matrix protein GM130.

GM130 and GRASP65 are Golgi peripheral membrane proteins that play a key role in Golgi stacking and vesicle tethering. However, the molecular details of their interaction and their structural role as a functional unit remain unclear. Here, we present the crystal structure of the PDZ domains of GRASP65 in complex with the GM130 C-terminal peptide at 1.96-Å resolution. In contrast to previous findings proposing that GM130 interacts with GRASP65 at the PDZ2 domain only, our crystal structure of the complex indicates that GM130 binds to GRASP65 at two distinct sites concurrently and that both the PDZ1 and PDZ2 domains of GRASP65 participate in this molecular interaction. Mutagenesis experiments support these structural observations and demonstrate that they are required for GRASP65-GM130 association.

Hu F ，Shi X ，Li B ，Huang X ，Morelli X ，Shi N ... -  《-》

Structural insight into Golgi membrane stacking by GRASP65 and GRASP55 proteins.

Feng Y ，Yu W ，Li X ，Lin S ，Zhou Y ，Hu J ，Liu X ... -  《-》

GRASP55, a second mammalian GRASP protein involved in the stacking of Golgi cisternae in a cell-free system.

Shorter J ，Watson R ，Giannakou ME ，Clarke M ，Warren G ，Barr FA ... -  《-》

Golgin45-Syntaxin5 Interaction Contributes to Structural Integrity of the Golgi Stack.

Tiwari N ，Graham M ，Liu X ，Yue X ，Zhu L ，Meshram D ，Choi S ，Qian Y ，Rothman JE ，Lee I ... -  《Scientific Reports》