Figure 3.

Allosteric sites in the TCR constant domains. Three allosteric sites identified by NMR (16, 17) in the Cα and Cβ domains of TCR A6 (PDB code 1QRN) (49) are boxed. Inset 1 shows the Cα AB loop and its surroundings in the TCR–CD3 structure (PDB code 6JXR) (23). The side chains of contacting residues are drawn in stick representation. The Cα AB loop contacts the CD3ϵ subunit of CD3ϵδ. Inset 2 shows the Cβ FG loop and its surroundings in the TCR–CD3 complex. The Cβ FG loop is situated immediately above the CD3ϵγ dimer but makes no direct contacts. Inset 3 shows the Cβ αA helix and its surroundings in the TCR–CD3 structure. The Cβ αA helix contacts the CP of the TCR α chain.