Crystal Structure of a Homogeneous IgG-Fc Glycoform with the N-Glycan Designed to Maximize the Antibody Dependent Cellular Cytotoxicity.
N-glycosylation on IgG modulates Fc conformation and effector functions. An IgG-Fc contains a human sialo-complex type (hSCT) glycan of biantennary structure with two α2,6-sialylations and without core-fucosylation is an optimized glycoform developed to enhance the antibody dependent cellular cytotoxicity (ADCC). hSCT modification not only enhances the binding affinity to Fc receptors in the presence of antigen but also in some cases provides gain-of-function effector activity. We used enzymatic glyco-engineering to prepare an IgG-Fc with homogeneous hSCT attached to each CH2 domain and solved its crystal structure. A compact form and an open form were observed in an asymmetric unit in the crystal. In the compact structure, the double glycan latches from the two hSCT chains stabilize the CH2 domains in a closed conformation. In the open structure, the terminal sialic acid (N-acetylneuraminic acid or NeuNAc) residue interacts through water-mediated hydrogen bonds with the D249-L251 helix, to modulate the pivot region of the CH2-CH3 interface. The double glycan latches and the sialic acid modulation may be mutually exclusive. This is the first crystal structure of glyco-engineered Fc with enhanced effector activities. This work provides insights into the relationship between the structural stability and effector functions affected by hSCT modification and the development of better antibodies for therapeutic applications.
Genomics Research Center, Academia Sinica , Taipei, Taiwan.|Chemical Biology and Molecular Biophysics program, Taiwan International Graduate Program, Academia Sinica , Taipei, Taiwan.|Institute of Biochemical Sciences, National Taiwan University , Taipei, Taiwan.
Chia-Lin
0000-0001-9490-6492
CL
Chen
Genomics Research Center, Academia Sinica , Taipei, Taiwan.
Jen-Chi
JC
Hsu
Genomics Research Center, Academia Sinica , Taipei, Taiwan.|Chemical Biology and Molecular Biophysics program, Taiwan International Graduate Program, Academia Sinica , Taipei, Taiwan.|Department of Chemistry, National Taiwan University , Taipei, Taiwan.
Chin-Wei
CW
Lin
CHO Pharma Inc. , Taipei, Taiwan.
Chia-Hung
CH
Wang
CHO Pharma Inc. , Taipei, Taiwan.
Ming-Hung
MH
Tsai
Genomics Research Center, Academia Sinica , Taipei, Taiwan.|Chemical Biology and Molecular Biophysics program, Taiwan International Graduate Program, Academia Sinica , Taipei, Taiwan.
Chung-Yi
CY
Wu
Genomics Research Center, Academia Sinica , Taipei, Taiwan.|Chemical Biology and Molecular Biophysics program, Taiwan International Graduate Program, Academia Sinica , Taipei, Taiwan.|Institute of Biochemical Sciences, National Taiwan University , Taipei, Taiwan.|Department of Chemistry, National Taiwan University , Taipei, Taiwan.
Chi-Huey
0000-0002-9961-7865
CH
Wong
Genomics Research Center, Academia Sinica , Taipei, Taiwan.|Chemical Biology and Molecular Biophysics program, Taiwan International Graduate Program, Academia Sinica , Taipei, Taiwan.
Che
C
Ma
D000920:Antibody-Dependent Cell Cytotoxicity; D018360:Crystallography, X-Ray; D015195:Drug Design; D006031:Glycosylation; D006801:Humans; D007141:Immunoglobulin Fc Fragments / Q000737:chemistry*; D007074:Immunoglobulin G / Q000737:chemistry*; D015394:Molecular Structure; D019158:N-Acetylneuraminic Acid / Q000737:chemistry; D011134:Polysaccharides / Q000737:chemistry*; D015202:Protein Engineering / Q000379:methods*
D007141:Immunoglobulin Fc Fragments; D007074:Immunoglobulin G; D011134:Polysaccharides; D019158:N-Acetylneuraminic Acid