The major histocompatibility complex class I antigen-binding protein p88 is the product of the calnexin gene

Proc Natl Acad Sci U S A. 1992 Sep 15;89(18):8452-6. 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 [35S]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 mu heavy chains and may serve as a chaperone for many membrane-bound polypeptides. A partial human p90 cDNA was cloned from a lambda gt11 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.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Antibodies, Monoclonal
  • Base Sequence
  • Blotting, Western
  • Calcium-Binding Proteins / genetics*
  • Calcium-Binding Proteins / immunology
  • Calcium-Binding Proteins / metabolism
  • Calnexin
  • Carcinoma, Hepatocellular
  • Cloning, Molecular
  • Endoplasmic Reticulum / metabolism
  • Histocompatibility Antigens Class I / metabolism*
  • Humans
  • Immunoenzyme Techniques
  • Immunoglobulin mu-Chains / metabolism
  • In Vitro Techniques
  • Macromolecular Substances
  • Molecular Sequence Data
  • Phosphoproteins / metabolism
  • Sequence Alignment
  • Tumor Cells, Cultured


  • Antibodies, Monoclonal
  • Calcium-Binding Proteins
  • Histocompatibility Antigens Class I
  • Immunoglobulin mu-Chains
  • Macromolecular Substances
  • Phosphoproteins
  • Calnexin

Associated data

  • GENBANK/M98452