PRIMARY STRUCTURE OF CLASS-II HUMAN HISTOCOMPATIBILITY ANTIGENS .2. AMINO-ACID-SEQUENCE OF THE N-TERMINAL-179 RESIDUES OF THE ALPHA-CHAIN OF AN HLA-DW2/DR2 ALLOANTIGEN

  • 1 January 1982
    • journal article
    • research article
    • Vol. 363  (6) , 671-676
Abstract
From a lymphoblastoid homozygous cell line (HLA-A3,3;B7,7;Dw2,2;DR2,2) the .alpha.-chain of the HLA-Dw2/DR2 antigen was isolated by an exclusively chemical procedure. The .alpha.- was separated from the .beta.-chain by chromatography with hydroxylapatite in Na-dodecyl sulfate. The amino acid sequence of the .alpha.-chain up to Position 179 is described. The molecule is divided into 2 domains which do not appear homologous to each other but show a significant homology to the .beta.-chain (21.2%). The similarity is larger in the 2nd (27%) than in the 1st (15.5%) domain, indicating a different evolutionary relationship for both parts. In contrast to the .beta.-chain, both domains contain an N-glycosidically linked carbohydrate. The methionines are positioned only in the N-terminal, the cysteines exclusively in the C-terminal domain. Only the latter can be stabilized by a disulfide bridge. As with the .beta.-chain the regions around the cysteines show a remarkable similarity with the constant C-terminal domains of .kappa.-, .gamma.-, .alpha.-, .gamma.-, .delta.-, .epsilon.- and .mu.-chains of Ig. Although to a considerably lesser extent, the .alpha.-chain preparation also shows a heterogeneity at the protein level. Since the employed cell-line is homozygous with regard to HLA-D/DR, at least 2 .alpha.-chain genes exist in the HLA-D/DR-region. With the already published sequence of the .beta.-chain, the extracellular part of an histocompatibility antigen of the HLA-D type is now known.

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