Solution structure of deglycosylated human IgG1 shows the role of C H 2 glycans in its conformation.

Autor: Spiteri VA; Department of Structural and Molecular Biology, Division of Biosciences, University College London, London, United Kingdom., Doutch J; ISIS Facility, STFC Rutherford Appleton Laboratory, Harwell Campus, Didcot, Oxfordshire, United Kingdom., Rambo RP; Diamond Light Source, Harwell Science and Innovation Campus, Didcot, Oxfordshire, United Kingdom., Gor J; Department of Structural and Molecular Biology, Division of Biosciences, University College London, London, United Kingdom., Dalby PA; Department of Biochemical Engineering, University College London, London, United Kingdom., Perkins SJ; Department of Structural and Molecular Biology, Division of Biosciences, University College London, London, United Kingdom. Electronic address: s.perkins@ucl.ac.uk.
Jazyk: angličtina
Zdroj: Biophysical journal [Biophys J] 2021 May 04; Vol. 120 (9), pp. 1814-1834. Date of Electronic Publication: 2021 Mar 04.
DOI: 10.1016/j.bpj.2021.02.038
Abstrakt: The human immunoglobulin G (IgG) class is the most prevalent antibody in serum, with the IgG1 subclass being the most abundant. IgG1 is composed of two Fab regions connected to a Fc region through a 15-residue hinge peptide. Two glycan chains are conserved in the Fc region in IgG; however, their importance for the structure of intact IgG1 has remained unclear. Here, we subjected glycosylated and deglycosylated monoclonal human IgG1 (designated as A33) to a comparative multidisciplinary structural study of both forms. After deglycosylation using peptide:N-glycosidase F, analytical ultracentrifugation showed that IgG1 remained monomeric and the sedimentation coefficients s 0 20,w of IgG1 decreased from 6.45 S by 0.16-0.27 S. This change was attributed to the reduction in mass after glycan removal. X-ray and neutron scattering revealed changes in the Guinier structural parameters after deglycosylation. Although the radius of gyration (R G ) was unchanged, the cross-sectional radius of gyration (R XS-1 ) increased by 0.1 nm, and the commonly occurring distance peak M2 of the distance distribution curve P(r) increased by 0.4 nm. These changes revealed that the Fab-Fc separation in IgG1 was perturbed after deglycosylation. To explain these changes, atomistic scattering modeling based on Monte Carlo simulations resulted in 123,284 and 119,191 trial structures for glycosylated and deglycosylated IgG1 respectively. From these, 100 x-ray and neutron best-fit models were determined. For these, principal component analyses identified five groups of structural conformations that were different for glycosylated and deglycosylated IgG1. The Fc region in glycosylated IgG1 showed a restricted range of conformations relative to the Fab regions, whereas the Fc region in deglycosylated IgG1 showed a broader conformational spectrum. These more variable Fc conformations account for the loss of binding to the Fcγ receptor in deglycosylated IgG1.
(Copyright © 2021 Biophysical Society. Published by Elsevier Inc. All rights reserved.)
Databáze: MEDLINE
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