Structural and functional analysis of yeast proteins involved in ER-to-Golgi transport: Sec24p family proteins and the GTPase activating protein Gyp5p

To maintain their intricate, internal structure of specialized compartments as well as meeting the necessity to react to changes of environmental conditions, eukaryotic cells have evolved an elaborate transport machinery to selectively deliver biochemical components to their various destinations. In this thesis some of the mechanisms that regulate the complex machinery of vesicular transport from the endoplasmic reticulum to the Golgi apparatus in the single-celled eukaryote Saccharomyces cerevisiae are described. I described the main characteristics of two close orthologues of the COPII component Sec24p, named Sfb2p and Sfb3p. These proteins are most likely actively involved in COPII vesicle formation and in cargo selection. In addition, I studied proteins involved in tethering/docking processes, in particular a new member of the Gyp family of GTPase activating proteins (GAPs), named Gyp5p, which shows remarkable specificity for the small Ras-like Ypt1 protein. Furthermore, I investigated the biological function of Ypt1p GTP hydrolysis in the cells.