| Modification Notes |
Soluble proteins in the endoplasmic reticulum (ER) contain a specific carboxy terminal sequence KDEL (Lys-Asp-Glu-Leu), and include the coat proteins required for vesicle budding from the ER, proteins that form retrograde vesicles on post-ER compartments, and integral membrane proteins that target vesicles to their correct destination. The retention of these soluble proteins in the ER depends on the interaction of the KDEL sequence with the corresponding KDEL receptor in the Golgi apparatus. When KDEL proteins reach the Golgi complex, they are recognized by the KDEL receptor and transported retrograde in COPI-coated vesicles back to the ER. A novel ligand ER protein 58 (EP58) shares no significant homology to any of the known ER-resident proteins. EP58 is primarily expressed in embryo, placenta, and adult heart. Sequence similarity to bacterial and fungus proteins suggests a possible role for EP58 in polysaccharide biosynthesis. |