Abstract
The influence of TAP-MHC class I interactions on peptide binding to the class I heavy chain is assessed during TAP-dependent assembly using Kb- specific Abs that recognize conformational changes induced by assembly with β2-microglobulin (β2m) and by peptide binding. A significant portion (45%) of Kb molecules in TAP+, RMA-derived microsomes are associated with the TAP complex as measured by coimmunoisolation of Kb using anti-TAP1 Abs, while only 20% of the Kb heavy chain molecules are isolated as Kbβ2m complexes with the α-Kb-specific Abs, Y-3 or K-10-56. The amount of Kb isolated with Y-3 and K-10-56 increases in proportion to transport and binding of peptide to the Kb molecules within the RMA microsomes. In contrast, less than 5% of the Kb within TAP2-RMA-S microsomes associated with the remaining TAP1 subunit. However, greater than 60% of Kb heavy chain is isolated as K-10-56- and Y-3-reactive Kbβ2m complexes. We propose that a TAP-MHC class I interaction serves to stabilize the MHC class I:β2m complex in an immature conformation (Y-3 and K-10-56 nonreactive) prior to high affinity peptide binding, preventing the export of class I molecules complexed with low affinity peptide ligands from the ER.
Original language | English (US) |
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Pages (from-to) | 4677-4684 |
Number of pages | 8 |
Journal | Journal of Immunology |
Volume | 162 |
Issue number | 8 |
State | Published - Apr 15 1999 |
ASJC Scopus subject areas
- Immunology and Allergy
- Immunology