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Updated: Aug 7, 2026

Measuring TCR-pMHC Binding In Situ using a FRET-based Microscopy Assay
Published on: October 30, 2015
The N-terminal region of tapasin is required to stabilize the MHC class I loading complex
N Bangia1, P J Lehner, E A Hughes
1Howard Hughes Medical Institute, Section of Immunobiology, Yale University School of Medicine, New Haven, CT 06520-8011, USA.
Abstract:
Tapasin mediates the binding of MHC class I molecules to the transporter associated with antigen processing (TAP). Deletion mutants of tapasin were used to examine the effect of tapasin on interactions within the MHC class I complex. Binding to TAP is mediated by the C-terminal region of tapasin. Michaelis-Menten analysis of peptide transport shows that this interaction is sufficient to increase TAP levels without significantly affecting the intrinsic translocation rate. Weak interactions exist between MHC class I molecules and TAP in the absence of tapasin, and between free heavy chains and TAP-tapasin complexes in the absence of beta2-microglobulin. The N-terminal 50 residues of tapasin constitute the key element which converts the sum of these weak interactions into a stable complex.
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