Calnexin is a chaperone, characterized by assisting protein folding and quality control, ensuring that only properly folded and assembled proteins proceed further along the secretory pathway. It specifically acts to retain unfolded or unassembled N-linked glycoproteins in the ER. Calnexin also functions as a chaperone for the folding of MHC class I α-chain in the membrane of the ER. As newly synthesized MHC class I α-chains enter the endoplasmic reticulum, calnexin binds on to them retaining them in a partly folded state.
