FIGURE 1.

a, superposition of CH2 domain structures extracted from the high resolution (≤2.5 Å) crystal structures of Fc and antibody deposited in the PDB. Although the β-strand region superimposes well, the loop comprising the Asn²⁹⁷ position (shown in blue) shows high structural variability. b, Ramachandran φ,ψ plot showing the backbone dihedral angle distribution of Asn²⁹⁷. Consistent with a, the Asn²⁹⁷ backbone has high structural variability and adapts φ positive conformation, which is an unique feature of Gly (38), in some of the crystal structures.