Tags: Protein.
HLA class II histocompatibility antigen DR alpha chain is a protein that in humans is encoded by the HLA-DRA gene. HLA-DRA encodes the alpha subunit of HLA-DR. Unlike the alpha chains of other Human MHC class II molecules the alpha subunit is practically invariable. However it can pair with in any individual the beta chain from 3 different DR beta loci DRB1 and two of any DRB3 DRB4 or DRB5 alleles.