The major histocompatibility complex class I antigen-binding protein p88 is the product of the calnexin gene.
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.
Galvin
K
K
Massachusetts General Hospital Cancer Center, Charlestown 02129.
Krishna
S
S
Ponchel
F
F
Frohlich
M
M
Cummings
D E
DE
Carlson
R
R
Wands
J R
JR
Isselbacher
K J
KJ
Pillai
S
S
Ozturk
M
M
D000595:Amino Acid Sequence; D000911:Antibodies, Monoclonal; D001483:Base Sequence; D015153:Blotting, Western; D002135:Calcium-Binding Proteins / Q000235:genetics* / Q000276:immunology / Q000378:metabolism; D037281:Calnexin; D006528:Carcinoma, Hepatocellular; D003001:Cloning, Molecular; D004721:Endoplasmic Reticulum / Q000378:metabolism; D015395:Histocompatibility Antigens Class I / Q000378:metabolism*; D006801:Humans; D007124:Immunoenzyme Techniques; D007148:Immunoglobulin mu-Chains / Q000378:metabolism; D066298:In Vitro Techniques; D046911:Macromolecular Substances; D008969:Molecular Sequence Data; D010750:Phosphoproteins / Q000378:metabolism; D016415:Sequence Alignment; D014407:Tumor Cells, Cultured
D000911:Antibodies, Monoclonal; D002135:Calcium-Binding Proteins; D015395:Histocompatibility Antigens Class I; D007148:Immunoglobulin mu-Chains; D046911:Macromolecular Substances; D010750:Phosphoproteins; D037281:Calnexin