Structural characterization of H-2 antigens purified from mouse liver.

Abstract

Papain-solubilized H-2a histocompatibility antigens (H-2k plus H-2Dd) were purified by a large-scale procedure that can routinely provide 2-3 mg of H- chain from 1 kg of mouse liver. The H-chains were homogeneous by sodium dodecyl sulfate electrophoresis. Disc gel electrophoresis resolved 2 protein bands that were identified as H-2Dd and H-2Kk by immune complex formation and autoradiography. Comparative amino acid composition and NH2-terminal sequence analyses of unfractionated H-2a, H-2Kk and HLA suggested close structural relationships. The following observations suggest that papain cleaves these membrane bound antigens at different positions with respect to the COOH terminus: the MW of the peptide portion of papain-solubilized HLA is smaller than that of H-2 (30,000 vs. 33,700); the COOH-terminal sequences are different; and papain-solubilized H-2 contains a free cysteine residue in addition to the 2 disulfide bridges that are present in H-2 and HLA.