 |
MHC class I
molecules are heterodimers composed of an a and a b subunit. |
|
The a subunit
is a 45 kDa polypeptide, inserted in the membrane, and
encoded by the MHC. |
|
The first two
structural domains of the a subunit - a1
and a2 -
associate to form the peptide-binding pocket and the membrane-distal region of the
molecule. |
|
The third
structural domain of the a subunit
-
a3 - noncovalently associates with the
b
subunit, or
b-2
microglobulin (b2m), forming the membrane-proximal region of
the molecule. |
|
b2m is a 12 kDa polypeptide not encoded by the MHC. |