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The Fab conformations in the solution structure of human IgG4 restricts access to its Fc region: implications for functional activity.

Rayner, LE; Hui, GK; Gor, J; Heenan, RK; Dalby, PA; Perkins, SJ; (2014) The Fab conformations in the solution structure of human IgG4 restricts access to its Fc region: implications for functional activity. J Biol Chem , 289 (30) pp. 20740-20756. 10.1074/jbc.M114.572404. Green open access

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Abstract

Human IgG4 antibody shows therapeutically-useful properties compared to the IgG1, IgG2 and IgG3 subclasses. Thus IgG4 does not activate complement, and shows conformational variability. These properties are attributable to its hinge region, which is the shortest of the four IgG subclasses. Using high throughput scattering methods, we have studied the solution structure of wild-type IgG4(Ser222) and a hinge mutant IgG4(Pro222) in different buffers and temperatures, where the proline substitution suppresses the formation of half-antibody. Analytical ultracentrifugation showed that both IgG4 forms were principally monomeric with sedimentation coefficients s020,w of 6.6-6.8 S. A monomer-dimer equilibrium was observed in heavy water buffer at low temperature. Scattering showed that the X-ray radius of gyration RG was unchanged with concentration in 50-250 mM NaCl buffers, while the neutron RG values showed a concentration-dependent increase as the temperature decreased in heavy water buffers. The distance distribution curves P(r) revealed two peaks, M1 and M2 that shifted below 2 mg/ml to indicate concentration-dependent IgG4 structures, in addition to IgG4 dimer formation at high concentration in heavy water. Constrained X-ray and neutron scattering modelling revealed asymmetric solution structures for IgG4(Ser222) with extended hinge structures. The IgG4(Pro222) structure was similar. Both IgG4 structures showed that their Fab regions were positioned close enough to the Fc region to restrict C1q binding. Our new molecular models for IgG4 explain its inability to activate complement, and clarifies aspects of its stability and function for therapeutic applications.

Type: Article
Title: The Fab conformations in the solution structure of human IgG4 restricts access to its Fc region: implications for functional activity.
Open access status: An open access version is available from UCL Discovery
DOI: 10.1074/jbc.M114.572404
Publisher version: http://dx.doi.org/10.1074/jbc.M114.572404
Additional information: © 2014 by The American Society for Biochemistry and Molecular Biology, Inc. Author's Choice—Final version full access. Creative Commons Attribution Unported License applies to Author Choice Articles
Keywords: X ray scattering, analytical ultracentrifugation, antibody, complement, constrained modelling, human IgG4, neutron scattering, protein structure
UCL classification: UCL
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Life Sciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Life Sciences > Div of Biosciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Life Sciences > Div of Biosciences > Structural and Molecular Biology
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science > Dept of Biochemical Engineering
URI: https://discovery.ucl.ac.uk/id/eprint/1431162
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