Figure 1.

Association of IgV domains in antibodies and ICR complexes: The arrangement of the CDR loops and CC′ loops of the V_H and V_L domains of antibodies is shown in panel a, where only CDR loops interact with the antigen. Panel b illustrates the positions of CC′ loop and FG loop of the IgV domain of ICR (PD-1:PD-L1) where the FG loop, front face and CC′ loop make key interactions with its cognate ligand. Panel c illustrates V_H and V_L domains of an antibody presented in cartoon representation (teal), where CC′ loop is coloured dark blue (in all panels of Fig. 1) and FG loop, red (in all panels of Fig. 1). Panel d illustrates the 2B4:CD48 complex (grey) where positions of CC′ loops (dark blue) and FG loop (red) are marked. The same is illustrated in PD-1:PD-L1 (forest green) shown in panel e and TIGIT:Nectin-2 (deep salmon) shown in panel f. The V_L domain (surface, teal, panel g) of the antibody was superposed with PD-1 of PD-1:PD-L1 complex, Nectin-2 of the TIGIT:Nectin-2 complex, 2B4 of the 2B4:CD48 complex. The position of CC′ loops and FG loops of V_H domain, PD-L1, TIGIT and CD48 are marked by ribbon representation, shown as thin rods connecting two central residues of the respective loops (Panel g).