| Abstract: |
The Ig superfamily members TCR and B cell receptor (BCR) share high structural and amino acid homology, yet interact with Ags in a distinct manner. The overall shape of the TCR ligand is rather constant, with the variation coming from the MHC polymorphism and the peptide heterogeneity. Consequently, the TCR α- and β-chains form a relatively flat ligand-binding site that interacts with the peptide:MHC (pep:MHC) ligand in a fixed diagonal orientation relative to the MHC α-helices, with the α- and β-chains of the TCR contacting the N and C termini of the pep:MHC complex, respectively. By contrast, the shape of BCR ligands varies dramatically, and the BCR exhibits much greater variability of the Ag-binding site. The mAbs 25-D1.16 (D1) and 22-C5.9 (C5), specific for the OVA-8:H-2Kb complex, allowed us to directly compare how TCR and BCR approach the same ligand. To that effect, we mapped D1 and C5 footprints over the OVA-8:H-2Kb complex. Using peptide variants and mutant MHC molecules, we show that the D1 and C5 contacts with the OVA- 8:Kb complex C terminus overlap with the TCR β-chain footprint, but that this footprint also extends to the regions of the molecule not contacted by the TCR. These studies suggest that D1 and C5 exhibit a hybrid mode of pep:MHC recognition, in part similar to that of the TCR β-chain and in part similar to the conventional anti-MHC Ab. |
| Keywords: |
nonhuman; protein conformation; animal cell; mouse; animals; mice; amino acid substitution; cell line; mice, transgenic; monoclonal antibody; antibodies, monoclonal; amino acid sequence; conserved sequence; immunoglobulin heavy chains; molecular sequence data; molecular recognition; antigen recognition; peptide fragments; ligands; binding site; antibody specificity; major histocompatibility complex; epitopes, t-lymphocyte; ligand binding; arginine; receptors, antigen, t-cell, alpha-beta; major histocompatibility antigen class 1; solvents; peptide analysis; egg proteins; ovalbumin; cytofluorometry; h-2 antigens; priority journal; article
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