Transport proteins in the plasma membrane and the secretory system

The organelles of the plant secretory system and the plasma membrane each contain a specific complement of resident integral membrane proteins, which provide each organelle with some of its unique characteristics. Over the past few years, genes encoding some of these proteins have been isolated and this has allowed the function and localization of the encoded proteins to be determined. A number of the genes encode proteins involved in transport processes, both in the trafficking of proteins between membranes and the transport of solutes across membranes. However, little is known about the majority of membrane proteins within the endomembrane system. A more complete understanding of the processes occurring within this system awaits the identification and analysis of many more of its components and the interactions between them. This will also allow important questions to be addressed regarding the mechanisms by which membrane proteins are correctly localized and assembled in the secretory pathway.