The COPII cage:: unifying principles of vesicle coat assembly

Communication between compartments of the exocytic and endocytic pathways in eukaryotic cells involves transport carriers-vesicles and tubules-that mediate the vectorial movement of cargo. Recent studies of transport-carrier formation in the early secretory pathway have provided new insights into the mechanisms of cargo selection by coat protein complex-II (COPII) adaptor proteins, the construction of cage-protein scaffolds and fission. These studies are beginning to produce a unifying molecular and structural model of coat function in the formation and fission of vesicles and tubules in endomembrane traffic.