Structural Insight into Golgi Membrane Stacking by GRASP65 and GRASP55 Proteins

Abstract

Background:The oligomerization of GRASP65 and GRASP55 is required to tether Golgi membranes. Results: The crystal structures reveal two types of intermolecular interactions, and biochemical and cellular assays confirm these observations. Conclusion: Two relatively weak interactions in combination are needed for GRASP-mediated Golgi stacking. Significance: These data suggest a novel mode of Golgi membrane stacking by the GRASP proteins.

Structural Basis for the Interaction between the Golgi Reassembly-stacking Protein GRASP65 and the Golgi Matrix Protein GM130

“…In contrast with previously reported structures of GRASP65 and GRASP55 (27,28), our GRASP65 construct undergoes substantial conformational changes. Although the individual PDZ domains are well aligned with previously reported structures, their relative position is rotated by 32.6°after GM130 binding.…”

“…These interactions have long been thought to play a major role in Golgi stacking (27,28,30). The analysis of GRASP65 and GRASP55 apo structures implies that GRASP clustering is mediated by an interaction between the end of the GRASP domain and the conventional peptide-binding groove on PDZ1.…”

“…Previous biochemical studies determined that GM130 only interacts with the PDZ2 domain of GRASP65 (24,26,29). For a long time, PDZ1 domains have been thought to interact with each other and play a substantial role in GRASP protein clustering to mediate cisternae stacking (27,28,30). Although GM130 and GRASP65 have been extensively studied, their mediation of Golgi stacking and vesicle tethering remains unclear, and structural information regarding their molecular recognition is currently lacking.…”

“…The crystal structures of the conserved N-terminal domains of both GRASP65 and GRASP55 have been elucidated (27,28) and indicate that they are composed of two circularly permuted PDZ-like domains, PDZ1 and PDZ2. Previous biochemical studies determined that GM130 only interacts with the PDZ2 domain of GRASP65 (24,26,29).…”

Structural and dynamic characterization of the Golgi Reassembly and Stacking Protein (GRASP) in solution

“…GRASP is a peripheral membrane protein, with an N-terminus structured into two PDZ domains exhibiting a protozoa PDZ folding, at least in vertebrates (GRASP domain) [64,65]. A second region in the GRASP structure, usually larger than the GRASP domain, consists of a nonevolutionary conserved domain that is rich in serine and proline (SPR domain) with regulatory function [63,127] and intrinsically disordered characteristics [174].…”