14 Role of TAP in class I MHC-associated antigen presentation
In a cell line lacking functional
TAP, class I molecules are not efficiently loaded with peptides and are degraded, mostly in the ER.
When a functional TAP gene is transfected into the cell line, normal assembly and expression of peptide-associated class I MHC molecules are restored.
Note that the TAP dimer may be attached to class I molecules by a linker protein called tapasin, which is not shown in this and other illustrations.