Calnexin contains a long (461 amino acids) N-terminal Ca2+ -binding domain extending into the lumen of the endoplasmic reticulum (ER), a short (22 amino acids) transmembrane segment and an acidic cytosolic domain (96 amino acids).
Calnexin binds newly synthesized glycoproteins and misfolded proteins and is believed to play a critical role in quality control processes during protein synthesis and folding. Calnexin acts as a lectin-like chaperone that binds oligosaccharide residues of newly synthesized N-linked glycoproteins. Calnexin has been shown to be associated with several cell surface proteins, including major histocompatibility complex (MHC) class I heavy chain, T-cell receptor (TCR), and B cell membrane immunoglobulin during translocation through the endoplasmic reticulum (ER). It also forms complexes with other resident ER proteins involved in Ca2+ -dependent retention of proteins.
