Rer1, a putative transmembrane domain receptor responsible for targeting proteins to the endoplasmic reticulum

Localization of resident proteins provides identity to subcellular compartm ents. Most proteins depend on a combination of both retention and retrieval to maintain their steady-state distribution. Rer1 is a putative receptor p rotein mediating retrieval of membrane proteins of the endoplasmic reticulu m. This retrieval relies on an unusual hydrophobic target sequence, the tra nsmembrane domain. Apart from Rer1, coatomer is also required to retrieve e scaped membrane proteins from the early Golgi region back to the endoplasmi c reticulum. Current evidence suggests that the Rer1-mediated retrieval of membrane proteins is a general sorting pathway in eukaryotic cells contribu ting to the maintenance of compartmental identity in the early secretory pa thway.