Sequence-To-Structure Dependence of Isolated and Bound Igg Fc Complex Biantennary N-Glycans: A Molecular Dynamics Study

PS1 Poster session 1 Odd numbers
Location (hall): 
Start/end time: 
Monday, July 1, 2019 - 15:45 to 17:15

Aoife Harbison1, Elisa Fadda1

1Maynooth University, Dublin, Ireland

Fc glycosylation of human immunoglobulins G (IgGs) is essential for their structural integrity and activity. Interestingly, the specific nature of the Fc glycoforms is known to modulate the IgG effector function. Indeed, while core-fucosylation of IgG Fc-glycans greatly affects the antibody-dependent cell-mediated cytotoxicity (ADCC) function, with obvious repercussions in the design of therapeutic antibodies, sialylation can reverse the antibody inflammatory response, and galactosylation levels have been linked to aging, to the onset of inflammation, and to the predisposition to rheumatoid arthritis. Within the framework of a structure-to-function relationship, we have studied the role of the N-glycan sequence on its intrinsic conformational propensity. We report the results of a systematic study, based on extensive molecular dynamics (MD) simulations in excess of 62 μs of cumulative simulation time, on the effect of sequence on the structure and dynamics of increasingly larger, complex biantennary N-glycoforms, i.e. from chitobiose to the larger N-glycan species commonly found in the Fc region of human IgGs. Our results show that while core fucosylation and sialylation do not affect the intrinsic dynamics of the isolated (unbound) N-glycans, galactosylation of the α(1-6) arm shifts dramatically its conformational equilibrium from an outstretched to a folded conformation. Following this, we used Replica Exchange Molecular Dynamics (REMD) to study the dynamics of the N-glycans linked to Asn297 of the Fc region of IgG1. From these intensive simulations, we gained a better insight into the conformational propensity of the bound N-glycans and the carbohydrate-carbohydrate/carbohydrate-protein interactions that are present.