Eukaryotic membrane traffic: retrieval and retention mechanisms to achieve organelle residence.

The localization of integral membrane proteins to specific organelles is necessary to maintain the functional integrity of eukaryotic cells. Recent studies indicate firstly, that retrieval and retention mechanisms, requiring specific primary sequence motifs, are used to ensure that proteins reside in specific membranes of the secretory and endocytic pathways and secondly, that these membranes exist as components of two juxtaposed systems separated by the cisternae of the Golgi stack.