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Science. 1997 Aug 29;277(5330):1306-9.

A critical role for tapasin in the assembly and function of multimeric MHC class I-TAP complexes.

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Howard Hughes Medical Institute, Section of Immunobiology, Yale University School of Medicine, 310 Cedar Street, New Haven, CT 06510, USA.


Newly assembled major histocompatibility complex (MHC) class I molecules, together with the endoplasmic reticulum chaperone calreticulin, interact with the transporter associated with antigen processing (TAP) through a molecule called tapasin. The molecular cloning of tapasin revealed it to be a transmembrane glycoprotein encoded by an MHC-linked gene. It is a member of the immunoglobulin superfamily with a probable cytoplasmic endoplasmic reticulum retention signal. Up to four MHC class I-tapasin complexes were found to bind to each TAP molecule. Expression of tapasin in a negative mutant human cell line (220) restored class I-TAP association and normal class I cell surface expression. Tapasin expression also corrected the defective recognition of virus-infected 220 cells by class I-restricted cytotoxic T cells, establishing a critical functional role for tapasin in MHC class I-restricted antigen processing.

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