Calnexin is encoded by the CNX gene and is a transmembrane protein chaperone associated with the ER. The function of calnexin is to assist in the folding of N-glycosylated proteins within the ER. The function of calnexin ensures that only glycoproteins that are properly folded and assembled continue further along the secretory pathway . Calnexin only binds to N-glycoproteins that have a Glc 1 Man 9 GlcNAc 2 oligosaccharide attached to an Asp residue. This structure results from glucosidase actions on the en bloc oligosaccharide (Glc 3 Man 9 GlcNAc 2 ) catalyzed first by glucosidase I (GluI) and then by glucosidase II (GluII). GluI is encoded by the mannosyl-oligosaccharide glucosidase (MOGS) gene. Functional GluII is composed of an α-subunit and a β-subunit. The GluII α-subunit gene is GANAB (glucosidase II alpha subunit) and the β-subunit gene is PRKCSH (protein kinase C substrate 80K-H). Calreticulin is encoded by the CALR gene. Calreticulin is a multifunctional protein whose primary function is to bind and sequester Ca 2+ ions in the lumen of the ER. Calreticulin also binds to misfolded proteins preventing them from being exported from the ER to the Golgi apparatus.