FOLDING OF VSV G-PROTEIN - SEQUENTIAL INTERACTION WITH BIP AND CALNEXIN

The endoplasmic reticulum (ER) contains molecular chaperones that faci litate the folding of proteins in mammalian cells. Biosynthetic labeli ng was used to study the interactions of two chaperones, BiP and calne xin, with vesicular stomatitis virus (VSV) glycoprotein (G protein). C oimmunoprecipitation of G protein with the chaperones showed that BiP bound maximally to early folding Intermediates of G protein, whereas c alnexin bound after a short lag to more folded molecules. Castanosperm ine, an inhibitor of ER glucosidases, blocked the binding of proteins to calnexin and inhibited G protein folding. Interaction with calnexin was necessary for efficient folding of G protein and for retention of partially folded forms.