Effects of N-Glycan Composition on Structure and Dynamics of IgG1 Fc and Their Implications for Antibody Engineering

• Published in: Scientific reports 2017-10, Vol.7 (1), p.12659-10, Article 12659
• Main Authors: Lee, Hui Sun, Im, Wonpil
• Format: Article
• Language: English
• Subjects: 631/45/221; 631/57/2266; Affinity; Antibodies; Antigens; Asparagine; Carbohydrates; Cytotoxicity; Fc receptors; Humanities and Social Sciences; Immunoglobulin G; Immunoglobulins; Mannose; Monoclonal antibodies; multidisciplinary; Polypeptides; Polysaccharides; Proteins; Science; Science (multidisciplinary); Signal transduction; Simulation
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/s41598-017-12830-5

Immunoglobulin G1 (IgG1), a subclass of human serum antibodies, is the most widely used scaffold for developing monoclonal antibodies to treat human diseases. The composition of asparagine(N)297-linked glycans can modulate the binding affinity of IgG1 Fc to Fc γ receptors, but it is unclear how the structural modifications of N-glycan termini, which are distal from the binding interface, contribute to the affinity. Through atomistic molecular dynamics simulations of a series of sequentially truncated high-mannose IgG1 Fc glycoforms, we found that the C′E loop and the Cγ2-Cγ3 orientation are highly dynamic, and changes in N-glycan composition alter their conformational ensembles. High-mannose glycoform preferentially samples conformations that are more competent to FcγRIIIa binding, compared to the truncated glycoforms, suggesting a role of IgG1 Fc N-glycan in optimizing the interface with the Fc receptor for efficient binding. The trajectory analyses also reveal that the N-glycan has large amplitude motions and the carbohydrate moiety interconverts between Fc-bound and unbound forms, enabling enzymatic modification of the glycan termini.