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Updated: Aug 8, 2026

In Situ Monitoring of Transiently Formed Molecular Chaperone Assemblies in Bacteria, Yeast, and Human Cells
08:58

In Situ Monitoring of Transiently Formed Molecular Chaperone Assemblies in Bacteria, Yeast, and Human Cells

Published on: September 2, 2019

The p88 molecular chaperone is identical to the endoplasmic reticulum membrane protein, calnexin

N Ahluwalia1, J J Bergeron, I Wada

  • 1Department of Biochemistry, University of Toronto, Ontario, Canada.

The Journal of Biological Chemistry
|May 25, 1992
PubMed

Insights

The molecular chaperone p88, involved in assembling murine class I histocompatibility molecules, is identical to calnexin. This finding reveals calnexin

Area of Science:

  • Cell Biology
  • Immunology
  • Molecular Biology

Background:

  • A novel molecular chaperone, p88, was previously identified for its role in murine class I histocompatibility molecule assembly.
  • p88 is hypothesized to promote proper assembly or retain class I molecules in the endoplasmic reticulum (ER) until ternary complex formation.
  • Calnexin is a known calcium-binding phosphoprotein of the ER membrane involved in protein folding and quality control.

Purpose of the Study:

  • To compare the molecular chaperone p88 with calnexin, a known ER membrane protein.
  • To determine if p88 and calnexin represent the same protein entity.
  • To elucidate the regulatory mechanisms of p88's interaction with class I molecules.

Main Methods:

  • Comparison of p88 and calnexin using a polyclonal anti-calnexin antiserum to assess shared antigenic epitopes.
  • Immunoprecipitation of both proteins in association with an intracellularly retained variant of the class I H-2Kb molecule.
  • Analysis by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), resistance to endoglycosidase H digestion, and peptide mapping (V8 protease and trypsin digestion).

Main Results:

  • p88 and calnexin share antigenic epitopes.
  • Both proteins were co-immunoprecipitated with a retained variant of the class I H-2Kb molecule.
  • Biochemical analyses (SDS-PAGE, endoglycosidase H resistance, peptide mapping) showed p88 and calnexin are indistinguishable.

Conclusions:

  • The molecular chaperone p88 is identified as calnexin.
  • This identification suggests p88/calnexin is a phosphorylated, calcium-binding protein of the ER membrane.
  • The findings provide insights into potential regulatory mechanisms governing the interaction of calnexin with class I molecules.

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