Class I MHC protein. A protein of this class consists of two chains. Notice that the α chain begins with two domains (α1, α2) that include α helices and continues with an immunoglobulin domain (α3), a transmembrane domain, and a cytoplasmic tail. The second chain, β2-microglobulin, adopts an immunoglobulin fold.
[Drawn from 1HHK.pdb.]