Characterization of an Incompletely Assembled Major Histocompatibility Class I Molecule (H-2Kb) Associated with Unusually Long Peptides: Implications for Antigen Processing and Presentation

• Published in: Proceedings of the National Academy of Sciences - PNAS 1994-05, Vol.91 (10), p.4145-4149
• Main Authors: Joyce, Sebastian, Kuzushima, Kiyotaka, Kepecs, Gilbert, Angeletti, Ruth Hogue, Nathenson, Stanley G.
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Amino acids; Animals; Antibodies; Antiserum; Biochemistry; Cell Line; Cell lines; Cellular biology; Cellular immunity; Chromatography, Affinity; Chromatography, High Pressure Liquid; H-2 Antigens - biosynthesis; H-2 Antigens - chemistry; H-2 Antigens - isolation & purification; Immunity (Disease); Methionine - metabolism; Mice; Molecular chains; Molecular Sequence Data; Molecules; Peptide Fragments - chemistry; Peptide Fragments - isolation & purification; Peptide Mapping; Rodents; Sequencing; T lymphocytes; Transplantation immunology; Tritium
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.91.10.4145

We have identified two forms of a major histocompatibility complex (MHC) class I molecule, H-2Kb, distinguishable by specific antibodies through a study of a genetically engineered mouse cell line that overexpresses these molecules. One form, a complex associated with β2-microglobulin (native, β2m+class I), is detectable by conformation-dependent antibodies. The other form, which remains after preclearing cell lysates of native class I, is only poorly, if at all, associated with β2-microglobulin (β2m-class I) and is detectable by an antiserum against the cytoplasmic tail region of H-2K molecules. Both forms are also present in normal cell lines. The affinity-purified native class I molecules bind short peptides (8 or 9 residues) and assemble tightly with β2-microglobulin. In striking contrast, the β2m-class I molecules bind peptides that are longer (>15 residues) than those bound to native class I molecules. This finding is consistent with the recent evidence that peptides longer than 8-10 amino acid residues are transported into the endoplasmic reticulum and suggests the possibility of a control step for peptide presentation by MHC in which the incompletely processed peptides bind to the heavy chain and a selected fraction undergoes final processing and presentation on the cell surface.