Strategic mutations in the class I major histocompatibility complex HLA-A2 independently affect both peptide binding and T cell receptor recognition.
Mutational studies of T cell receptor (TCR) contact residues on the surface of the human class I major histocompatibility complex (MHC) molecule HLA-A2 have identified a "functional hot spot" that comprises Arg(65) and Lys(66) and is involved in recognition by most peptide-specific HLA-A2-restricted TCRs. Although there is a significant amount of functional data on the effects of mutations at these positions, there is comparatively little biochemical information that could illuminate their mode of action. Here, we have used a combination of fluorescence anisotropy, functional assays, and Biacore binding experiments to examine the effects of mutations at these positions on the peptide-MHC interaction and TCR recognition. The results indicate that mutations at both position 65 and position 66 influence peptide binding by HLA-A2 to various extents. In particular, mutations at position 66 result in significantly increased peptide dissociation rates. However, these effects are independent of their effects on TCR recognition, and the Arg(65)-Lys(66) region thus represents a true "hot spot" for TCR recognition. We also made the observation that in vitro T cell reactivity does not scale with the half-life of the peptide-MHC complex, as is often assumed. Finally, position 66 is implicated in the "dual recognition" of both peptide and TCR, emphasizing the multiple roles of the class I MHC peptide-binding domain.
Baxter
Tiffany K
TK
Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556, USA.
Gagnon
Susan J
SJ
Davis-Harrison
Rebecca L
RL
Beck
John C
JC
Binz
Anne-Kathrin
AK
Turner
Richard V
RV
Biddison
William E
WE
Baker
Brian M
BM
D000595:Amino Acid Sequence; D001120:Arginine / Q000378:metabolism; D018984:Epitopes, T-Lymphocyte; D005805:Genes, MHC Class I; D015789:HLA-A2 Antigen / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D008239:Lysine / Q000378:metabolism; D008285:Major Histocompatibility Complex; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation; D010455:Peptides / Q000378:metabolism*; D011485:Protein Binding; D011487:Protein Conformation; D011948:Receptors, Antigen, T-Cell / Q000235:genetics / Q000378:metabolism*; D013601:T-Lymphocytes / Q000166:cytology / Q000378:metabolism; D013816:Thermodynamics
D018984:Epitopes, T-Lymphocyte; D015789:HLA-A2 Antigen; D010455:Peptides; D011948:Receptors, Antigen, T-Cell; D001120:Arginine; D008239:Lysine