Structure of MHC class I and II

Since the principal role of MHC encoded proteins is the presentation of peptide antigen, all such proteins have an antigen-binding groove. The floor of the groove is provided by a beta sheet region upon which rests two alpha helical regions. MHC class I and II proteins differ in the details of structure and function. The large figures show the MHC molecules viewed "face on" as they would be encountered by T cell receptors. The inset figures depict the MHC molecules as viewed "side on."