Chaperone selection during glycoprotein translocation into the endoplasmicreticulum

A variety of molecular chaperones and folding enzymes assist the folding of newly synthesized proteins in the endoplasmic reticulum. Here we investiga ted why some glycoproteins interact with the molecular chaperone sip, and o thers with the calnexin/calreticulin pathway. The folding of Semliki forest virus glycoproteins and influenza hemagglutinin was studied in Living cell s. The initial choice of chaperone depended on the Location of N-linked gly cans in the growing nascent chain. Direct interaction with calnexin and cal reticulin without prior interaction with BiP occurred if glycans were prese nt within about 50 residues of the protein's NH2-terminus.