HLA class I histocompatibility antigen, alpha chain E (HLA-E) HLA-E belongs to the HLA class I heavy chain paralogues. HLA-E is a class I molecule heterodimer consisting of a heavy chain and a light chain (beta-2 microglobulin). The heavy chain is anchored in the membrane. HLA-E binds a restricted subset of peptides derived from the leader peptides of other class I molecules. It is one of a family of molecules known as MHC class Ib and has a very specialized role in cell recognition by NK cells (Natural Killer). HLA-E is very highly conserved and presents a small repertoire of peptides of various origins.