Figure 4.

Intramolecular interaction networks of the IgG1-Fc glycans. A pair of contact residues between the N-glycan and the polypeptide chain or between the two N-glycans found within 4 Å is connected by a line segment for the crystal structures of (a) Fc alone (3AVE) and (b) sFcγRIIIa-bound Fc (5XJE). The terminal galactose residues of α1-6Man branch in 3AVE were modeled as described in the Materials and Methods. The contact pairs involving either of these galactose residues are conserved in the crystal structure 5IW3, which gave electron densities of the terminal galactose residues. (c) Pairs of contact residues found within 4 Å in the ensemble model derived from the MD simulation are connected by different types of line segments (red for carbohydrate-protein contact and cyan for carbohydrate-carbohydrate contact) according to incidence as follows: More than 24,000 pairs (thick solid line), 24,000 to 16,000 pairs (thin solid line), and 16,000 to 8,000 pairs (dashed line).