RAP, A NOVEL TYPE OF ER CHAPERONE

Members of the low-density lipoprotein (LDL) receptor gene family play an important role in cellular uptake of various extracellular ligands . Recent studies have shown that a 39-kDa protein known as RAP (recept or-associated protein) serves as a molecular chaperone to assist the f olding of certain LDL-receptor family proteins and their passage throu gh the secretory pathway. In this review, the authors discuss our curr ent understanding of the roles of RAP as a molecular chaperone/escort protein and present a model of how RAP might carry out these functions .