Binding of a Nonapeptide by MHC class I and the TCR Receptor
The image at the right shows the structure of the MHC class I protein whioch is embedded in the plasma membrane. There are two polypeptides: the alpha chain and the beta2 microglobulin. The alpha chain has five domains: alpha-1, alpha-2 and alpha-3, which are on the outside of the plasma membrane, a transmembrane domain and a cytoplasmic domain. Only the alpha chain is involved in the binding of the antigenic peptide and the antigenic peptide is bound in a pocket between the alpha-1 and alpha-2 domain.
Class I variability (Pop-Up Box)
In order to crystallize the protein, the extracellular domain was cleaved from the rest of the protein using the proteolytic enzyme, papain. The crystal structure of the extracellular portion of the molecule together with its interactions with the TCR receptor and sites of hypervariability are shown in the Chime presentation