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Title: Mouse IgG2c Fc loop residues promote greater receptor-binding affinity than mouse IgG2b or human IgG1

Journal Article · · PLoS ONE
 [1]; ORCiD logo [1]
  1. Iowa State Univ., Ames, IA (United States)
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The structures of non-human antibodies are largely unstudied despite the potential for the identification of alternative structural motifs and physical properties that will benefit a basic understanding of protein and immune system evolution as well as highlight unexplored motifs to improve therapeutic monoclonal antibody. Here we probe the structure and receptor-binding properties of the mouse IgG2c crystallizable fragment (Fc) to compare to mouse IgG2b and human IgG1 Fcs. Models of mIgG2c Fc determined by x-ray crystallography with a complex-type biantennary (to 2.05 Å) or a truncated (1)GlcNAc asparagine-linked (N)-glycan attached (to 2.04 Å) show differences in key regions related to mouse Fc γ receptor IV (mFcγRIV) binding. Mouse IgG2c forms different non-bonded interactions between the BC, DE and FG loops than the highly-conserved mIgG2b and binds to FcγRIV with 4.7-fold greater affinity in the complex-type glycoform. Secondary structural elements surrounding the Asn297 site of glycosylation form longer beta strands in the truncated mIgG2c Fc glycoform when compared to mIgG2c with the complex-type N-glycan. Solution NMR spectroscopy of the N-linked (1)GlcNAc residues show differences between mIgG2b, 2c and hIgG1 Fc that correlate to receptor binding affinity. Mutations targeting differences in mIgG2 DE and FG loops decreased affinity of mIgG2c for FcγRIV and increased affinity of mIgG2b. Changes in NMR spectra of the mutant Fc proteins mirrored these changes in affinity. Our studies identified structural and functional differences in highly conserved molecules that were not predicted from primary sequence comparison.

Research Organization:
Argonne National Laboratory (ANL), Argonne, IL (United States). Advanced Photon Source (APS)
Sponsoring Organization:
National Institutes of Health (NIH); National Institute of General Medical Sciences (NIGMS); Roy J. Carver Department of Biochemistry, Biophysics & Molecular Biology at Iowa State University; USDOE
Grant/Contract Number:
R01 GM115489; GUP-48455
OSTI ID:
1433703
Journal Information:
PLoS ONE, Vol. 13, Issue 2; ISSN 1932-6203
Publisher:
Public Library of ScienceCopyright Statement
Country of Publication:
United States
Language:
ENGLISH
Citation Metrics:
Cited by: 7 works
Citation information provided by
Web of Science

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Cited By (3)

Utility of High Resolution NMR Methods to Probe the Impact of Chemical Modifications on Higher Order Structure of Monoclonal Antibodies in Relation to Antigen Binding journal July 2019
From Rhesus macaque to human: structural evolutionary pathways for immunoglobulin G subclasses journal April 2019
A synopsis of recent developments defining how N-glycosylation impacts immunoglobulin G structure and function journal September 2019

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Related Subjects

59 BASIC BIOLOGICAL SCIENCES
Mice
Crystals
NMR spectroscopy
Crystallization
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Crystal structure
Immune system
Protein structure