Critical residues of ICAM-4 involved in interaction with β2 integrins and location of ICAM-4 peptides that mediate adhesion to CD11c/CD18 integrin. (A) Three-dimensional representation of an ICAM-4 model constructed on the basis of ICAM-2 structure. Amino acids are designated by 3-letter codes and residue numbers. The solvent-accessible surfaces of ICAM-4 residues that when mutated cause a decrease in adhesion to CD11a/CD18 (left), CD11b/CD18 (middle), and CD11c/CD18 (right) are colored (Trp, orange; Arg, cyan; Leu, green; Thr, magenta; Glu, red). (B) A ribbon diagram of ICAM-4 displayed in 3 orientations 120 degrees to one another. The strands of the antiparallel β sheets are labeled by capital letters. The locations of the ICAM-4 peptides are colored: P-D1 (PQPQNSSLRTPLR), residues 44 to 56 (cyan); P-D2 (VTLTYEFAAGPRD), residues 161 to 173 (red). Side chains of the 2 peptide residues found to be involved in CD11c/CD18 binding by mutagenesis studies are shown as ball and stick.
