Lectin-deficient Calnexin Is Capable of Binding Class I Histocompatibility Moleculesin Vivoand Preventing Their Degradation

摘要: Calnexin is a membrane-bound lectin of the endoplasmic reticulum (ER) that binds transiently to newly synthesized glycoproteins. By interacting with oligosaccharides form Glc1Man9GlcNAc2, calnexin enhances folding glycoprotein substrates, retains misfolded variants in ER, and some cases participates their degradation. has also been shown bind polypeptides vivo do not possess glycan this function vitro as molecular chaperone for nonglycosylated proteins. To test relative importance site compared polypeptide-binding site, we have generated six mutants defective oligosaccharide binding using site-directed mutagenesis. Expressed glutathione S-transferase fusions, these were still capable ERp57, thiol oxidoreductase, preventing aggregation substrate, citrate synthase. They were, however, unable Glc1 Man9GlcNAc2 compromised monoglucosylated substrate jack bean α-mannosidase. Two then engineered into full-length heterologous expression Drosophila cells along murine class I histocompatibility molecules Kb Db model In system, site-defective was able replace wild type forming complex heavy chains Thus, at least molecules, dispensable its functions.