Molecular Chaperones in MHC Class I and Class II Biosynthesis and Assembly

  • Sumati Rajagopalan


MHC class I and class II molecules are multisubunit receptors that require correct assembly of their individual subunits prior to cell surface expression. MHC class I molecules are comprised of a polymorphic transmembrane heavy chain and a soluble protein termed beta 2-microglobulin (β2m) in association with a peptide ligand, whereas MHC class II molecules consist of transmembrane α and β chains in association with peptide. The endoplasmic reticulum (ER) is the cellular compartment where newly synthesized MHC molecules fold and assemble to attain correct quarternary structure. In addition to providing an oxidizing environment that favors formation of disulphide bonds, the ER contains a number of resident proteins that facilitate the folding and assembly of MHC-peptide complexes. These proteins are collectively known as molecular chaperones and by definition, while they bind and stabilize newly synthesized polypeptides and partially folded intermediates, they are not part of the final assembled cell surface protein complex (reviewed in ref. 1). Molecular chaperones are thus components of the quality control system that allows productive folding and assembly events to proceed efficiently, while ensuring the ER retention and degradation of misfolded and incompletely assembled proteins. This chapter focuses on the molecular chaperones implicated in class I and class II biosynthesis and assembly.


Heavy Chain Major Histocompatibility Complex Class Molecular Chaperone Major Histocompatibility Complex Molecule Transporter Associate With Antigen Processing 
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© R.G. Landes Company 1996

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  • Sumati Rajagopalan

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