NMR assignments of the N-glycans of the Fc fragment of mouse immunoglobulin G2b glycoprotein.

Saeko Yanaka, Yoshiki Yamaguchi, Takeshi Takizawa, Yohei Miyanoiri, Rina Yogo, Ichio Shimada, Koichi Kato

Biomolecular NMR assignments 2021 Apr

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The Fc portion of immunoglobulin G (IgG) promotes defensive effector functions in the immune system by interacting with Fcγ receptors and complement component C1q. These interactions critically depend on N-glycosylation at Asn297 of each CH2 domain, where biantennary complex-type oligosaccharides contain microheterogeneities resulting primarily from the presence or absence of non-reducing terminal galactose residues. Crystal structures of Fc have shown that a pair of N-glycans is located between the two CH2 domains. Here we applied our metabolic isotope labeling technique using mammalian cells for in-solution structural characterization of mouse IgG2b-Fc glycoforms with a molecular mass of 54 kDa. Based on spectral assignments of the N-glycans as well as polypeptide backbones of Fc, we probed conformational perturbations of Fc induced by N-glycan trimming, especially enzymatic degalactosylation. The results indicated that degalactosylation structurally perturbed the Fc region through rearrangement of glycan-protein interactions. The spectral assignments of IgG2b-Fc glycoprotein will provide the basis for NMR investigation of its dynamic conformations and interactions with effector molecules in solution.

Citation

Saeko Yanaka, Yoshiki Yamaguchi, Takeshi Takizawa, Yohei Miyanoiri, Rina Yogo, Ichio Shimada, Koichi Kato. NMR assignments of the N-glycans of the Fc fragment of mouse immunoglobulin G2b glycoprotein. Biomolecular NMR assignments. 2021 Apr;15(1):187-192