Primary Structure of Pooled, Papain‐solubilized HLA‐A, ‐B, and ‐C Antigens

Abstract

The tentative amino acid sequence of pooled, papain-solubilized HLA antigen H chains was determined. The amino acid sequence comprises 273 residues. As the structural analyses were performed on HLA antigen H chains comprising a mixture of several allelic forms derived from the A, B and possibly C loci, multiple residues were encountered in several positions. A quantitatively dominating residue could always be easily identified. Apparently the amino acid variability of the HLA-A, -B and -C antigens is found in restricted regions of the molecule. The COOH-terminal third of the HLA antigen H chain appears to be less variable than other regions of the molecule. Previous work showed that the HLA antigen H chain contains 2 immunoglobulin-like disulfide loops. The COOH-terminal third of the H chain was similar in primary structure to .beta.2-microglobulin and the immunoglobulin G constant domains.