Crystal Structures of the Single PDZ Domains from GRASP65 and their Interaction with the Golgin GM130

Among the major components of the Golgi apparatus are the GRASP family proteins, including GRASP65 on the cis-Golgi side. With its GRASP domain, GRASP65 is involved in Golgi stacking and ribbon formation. Interaction of GRASP65 with the Golgi marker protein GM130 is important for the docking of vesicles to the Golgi membrane. We present here structures of the two individual PDZ domains comprising the GRASP domain in human GRASP65. We use isothermal titration calorimetry to probe the interaction between GRASP65 and GM130. Additionally, we present evidence for the limited sequence conservation of the PDZ fold by describing the PDZ domain structure of the GRASP65 homolog Grh1 from Saccharomyces cerevisiae.