UGGT is part of the ER quality control system of glycoprotein folding and its activity increases the potential for correctly folded glycoproteins.The main proteins involved in the ER quality control system are UGGT, the ER lectin chaperones (calnexin and calreticulin), and glucosidase II. UGGT first recognizes the incompletely folded glycoprotein and monoglucosylates it. The lectins, calnexin and calreticulin, have high affinities for monoglucosylated proteins and the ER chaperones that associate with these lectins assist the folding of the misfolded glycoprotein. Subsequently, glucosidase II will deglucosylate the glycoprotein. If the glycoprotein is still misfolded, UGGT will re-glucosylate it and allow it to go through the cycle again.