Complete amino acid sequence of an HLA-DR antigen-like beta chain as predicted from the nucleotide sequence: similarities with immunoglobulins and HLA-A, -B, and -C antigens.

Abstract

The complete nucleotide sequence of an HLA-DR antigen-like .beta.-chain c[complementary]DNA clone were determined. The 1080 base pairs include the complete coding region and most of the untranslated portion. The predicted amino acid sequence has 229 residues. The .beta. chain contains 2 Ig-like disulfide loops and a 21-amino acid residue membrane-integrated segment. Ten amino acid residues reside on the cytoplasmic side of the plasma membrane. The single asparagine-linked carbohydrate moiety is attached to asparagine-19. The NH2-terminal 91 residues of the .beta. chain are homologous to the corresponding region of HLA-A, -B and -C antigen H chains. Residues 92-192 of the .beta. chain display statistically significant homology to members of the Ig family, .beta.2-microglobulin, and the Ig+-like domain of HLA-A, -B and -C antigen H chains. The major histocompatibility antigens of class I and class II type and the constant regions of Ig+ apparently are evolutionarily related.