The Major Histocompatibility Complex Class I Antigen-Binding Protein p88 is the Product of the Calnexin Gene

• Published in: Proceedings of the National Academy of Sciences - PNAS 1992-09, Vol.89 (18), p.8452-8456
• Main Authors: Galvin, K., Krishna, S., Ponchel, F., Frohlich, M., Cummings, D. E., Carlson, R., Wands, J. R., Isselbacher, K. J., Pillai, S., Ozturk, M.
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Antibodies; Antibodies, Monoclonal; antigen-binding protein; B lymphocytes; Base Sequence; Biological and medical sciences; Blotting, Western; Calcium-Binding Proteins - genetics; Calcium-Binding Proteins - immunology; Calcium-Binding Proteins - metabolism; Calnexin; Carcinoma, Hepatocellular; cDNA; Cell lines; Cellular metabolism; Cloning, Molecular; Complementary DNA; Endoplasmic Reticulum - metabolism; Fundamental and applied biological sciences. Psychology; genes; Hepatocellular carcinoma; Histocompatibility Antigens Class I - metabolism; Humans; Immunity (Disease); Immunoenzyme Techniques; Immunoglobulin mu-Chains - metabolism; In Vitro Techniques; Macromolecular Substances; major histocompatibility complex; man; Medical research; Molecular and cellular biology; Molecular genetics; Molecular Sequence Data; Molecules; nucleotide sequence; Phosphoproteins; Phosphoproteins - metabolism; predictions; Proteins; Receptors; Sequence Alignment; Translation. Translation factors. Protein processing; Tumor Cells, Cultured
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.89.18.8452

A 90-kDa phosphoprotein (p90) of the endoplasmic reticulum was identified by a monoclonal antibody generated against human hepatoma cells. Pulse-chase experiments with [32P]phosphate and [k35S]methionine demonstrated that p90 formed both stable and transient complexes with other cellular proteins, suggesting its role as a molecular chaperone. This protein associates with heavy chains of major histocompatibility complex class I proteins, suggesting that it is the human homolog of the recently described 88-kDa protein that transiently associates with murine class I molecules in the endoplasmic reticulum. The p90 protein also associates in B lymphocytes with membrane immunoglobulin μ heavy chains and may serve as a chaperone for many membrane-bound polypeptides. A partial human p90 cDNA was cloned from a λgt11 expression library and identified as the human homolog of calnexin, a major canine calcium-binding protein found to be associated with the signal-sequence receptor in endoplasmic reticulum membranes.