Comprehensive analysis of structural and sequencing data reveals almost unconstrained chain pairing in TCRαβ complex
Fig 7
Characteristic residue contacts of MAIT TCRs.
a. Scatter-plot of amino acid pair enrichment at contacting residues for the Jα gene choice of MAIT T-cells versus overall enrichment observed for given contact residues in the PairSEQ dataset. Y axis shows the log ratio of amino acid pair probabilities for VαJαVβ combinations corresponding to MAIT T-cells and those with a free choice for the Jα gene. X axis shows observed to expected amino acid pair count ratio at contacting residues in the PairSEQ dataset. Residue pairs with enriched amino acid pairs coming from MAIT Jα gene choice (y > 0.25, corresponding to ~19% increase in frequency) are colored in red and labeled. Not that overall enrichment for corresponding amino acid pairs in the PairSEQ dataset is relatively moderate (x < 0.125, corresponding to ~9% increase in frequency). b.-d. Structural data showing Glutamine (GLN, Q) at α108 and Tyrosine (TYR, Y) at β55 interacting with an Arginine (ARG) of MHC alpha-1 helix domain in the MAIT:MR1 complex. MR1 complex structures are shown in b (4pj7) and c (5u1r), d shows an non-MAIT TCR (having the same amino acids at α108 and β55) in complex with MHCI (4jry). Polar contacts between GLN:ARG and TYR:ARG are shown with dotted lines in b and c, but are absent in d. PDB structure chain coloring: green for MHC, yellow for TCRα and pink for TCRβ; antigen peptide in d is shown with purple.