The superposition is based on the MHC molecules’ peptide-binding groove. For clarity, only TCR V modules and one MHC groove are depicted. Left panel: Selected class I TCR molecules are 2CKB in blue-grey, 1QSE in purple, 3SJV in dark blue, 1QGA in pink, 1BD2 in yellow, 2VLJ in silver, 2AK4 in gold, 3FFC in light blue and 1MT5 in red. Right panel: Selected class II TCR molecules are 1D9K in yellow, 1FYT in cyan, 1U3H in pale-green, 1YYM in dark blue, 3C5Z in sand, 3RDT in bluewhite, and 2IAM in smudge.