Complete amino acid sequence of pooled papain-solubilized HLA-A, -B, and -C antigens: relatedness to immunoglobulins and internal homologies.

Abstract

Pooled, papain-solubilized HLA-A, -B and -C antigens, derived from a large number of individuals and comprising several allelic forms, were subjected to amino acid sequence determination. Despite the heterogeneity of the material, a main sequence representing all of the 273 amino acid residues could be established. The primary structure encompassed 2 immunoglobulin[Ig]-like disulfide loops. The single carbohydrate moiety was attached to aspargine-86. Computer analyses demonstrated that the COOH-terminal 1/3 of the sequence, called H3, displayed statistically significant homology with members of the Ig family. The NH2-terminal 2/3 of the molecule, called H1 and H2, were not significantly homologous to any of the Ig sequences. H1 and H2 exhibit a distant relatedness to each other but no obvious similarity to the H3 region.