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Updated: Aug 12, 2026

Characterization of Multi-subunit Protein Complexes of Human MxA Using Non-denaturing Polyacrylamide Gel-electrophoresis
Published on: October 28, 2016
A role for calnexin (IP90) in the assembly of class II MHC molecules
1Section of Immunobiology, Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, CT 06510.
Abstract:
Major histocompatibility complex (MHC) class II antigens consist of alpha and beta chains that associate intracellularly with the invariant (I) chain. The HLA-DR alpha beta I complex assembles in the endoplasmic reticulum (ER) into a nonameric structure via progressive addition of three alpha beta dimers to a core invariant chain trimer. We have examined intracellular association of alpha beta I complexes with the resident ER protein calnexin. Calnexin associates rapidly (within 3 min) with newly synthesized alpha, beta and I chains, and remains associated with the assembling alpha beta I complex until the final alpha beta dimer is added, forming the complete nonamer. Dissociation of calnexin parallels egress of alpha beta I from the ER. These results suggest that calnexin retains and stabilizes both free class II subunits and partially assembled class II-I chain complexes until assembly of the nonamer is complete.
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