Impact of the N-glycosylation on full-length IgG2 and IgG4 antibodies: a comparative study using molecular dynamics simulations.

Monoclonal antibodies are among the most important biomolecules in the pharmaceutic field. They could undergo several post-translational modifications, most notably N-glycosylation, yet the effect of these glycans remains poorly understood at the atomistic level, and the few existing studies focus on the prevalent immunoglobulin G1. We compared N-glycosylation in two structurally divergent monoclonal antibodies, Mab231, a murine IgG2a, and pembrolizumab, a human IgG4, which differ in species, sequence, architecture, and in the location and composition of their glycans. Using molecular dynamics simulations, we studied both antibodies with and without their glycans. In both, the glycan interactions extend beyond the Fc to reach Fab residues, more so for the more mobile Fc glycan and differently in the two antibodies. Allosteric network calculations reveal a potential impact of the glycan that can affect the Fab framework regions, which could in turn affect antigen binding. The glycans do not drastically alter the conformational landscape, and neither the inter-domain correlated motions nor the orientation of the Fab arms relative to the Fc can be resolved as glycan effects at three replicates per system. We also find that the effect of the Fc glycans on CH2 opening depends on the geometric criterion used, which underscores the need to consider full-length structures and the diversity of IgG scaffolds in glyco-engineering.