16 – Vesicular Transport

Publisher Summary This chapter explores the vesicular transport. The newly synthesized proteins destined for the plasma membrane are imported into the ER where they oligomerize after folding, receive N-linked oligosaccharides, and are then checked by the quality control machinery before export from the transitional ER through vesicular intermediates. This chapter puts together a brief note on COPI and COPII, describing a role for coat proteins in cargo selection. The existence of transport vesicles as transport intermediates in the secretory pathway has never been universally accepted. Transport vesicles are supported by a large body of evidence derived from morphological, molecular, genetic as well as biochemical studies. The need for GTP hydrolysis therefore suggests that for proper sorting to take place, coatomer needs to cycle on and off the membrane. This chapter also stresses that the role of cargo molecules in vesicle formation has been so far underscored through their ability to interact directly with coat proteins. Important insights into the mechanism of a complex reaction can also be obtained by studying the kinetics of the process. If this is how sorting occurs remains to be tested but importantly, these studies show that simple parameters can define models that predict the asymmetric distributions, offering clues to how the secretory pathway operates.