The last two residues of the structure are omitted. Hydrogen bonds at the boundary between domains 1 and 2.
Open circles represent conserved loop structures.
The dimer interface and ligand-binding residues. Side chains are shown for residues that interact across the dimer interface in domain 1. Salt bridges between residues at the periphery of the interface are dashed lines. A model for the ICAM-1 dimer on the cell surface. Domains 1 and 2 and their orientation in the dimer are from the crystal structure.