PROTEIN SORTING BY TYROSINE-BASED SIGNALS - ADAPTING TO THE YS AND WHEREFORES

The endocytic and secretory pathways of eukaryotic cells consist of an away of membrane-bound compartments, each of which contains a charact eristic cohort of transmembrane proteins. Understanding how these prot eins are targeted to and maintained within their appropriate compartme nts will be crucial for unravelling the mysteries of organelle biogene sis and function. A common event in the sorting of many transmembrane proteins is the interaction between a sorting signal in the cytosolic domain of the targeted protein and a component of an organellar protei n coat. Here, we summarize recent findings on the mechanism of sorting by one type of signal, characterized by the presence of a critical ty rosine (Y) residue, and attempt to integrate these findings into a hyp othetical model for protein sorting in the endocytic and late (post-Go lgi) secretory pathways.