%0 Journal Article %A Hui, G. K. %A Wright, D. W. %A Vennard, Owen L. %A Rayner, L. E. %A Pang, M. %A Yeo, See Cheng %A Gor, J. %A Molyneux, Karen %A Barratt, Jonathan %A Perkins, S. J. %D 2016 %T The solution structures of native and patient monomeric human IgA1 reveal asymmetric extended structures: implications for function and IgAN disease. %U https://figshare.le.ac.uk/articles/journal_contribution/The_solution_structures_of_native_and_patient_monomeric_human_IgA1_reveal_asymmetric_extended_structures_implications_for_function_and_IgAN_disease_/10129061 %2 https://figshare.le.ac.uk/ndownloader/files/18254663 %K X-ray scattering %K analytical ultracentrifugation %K antibody %K constrained modelling %K human immunoglobulin A1 (IgA1) %K immunoglobulin A (IgA) nephropathy %K neutron scattering %K Crystallography, X-Ray %K Female %K Glomerulonephritis, IGA %K Humans %K Immunoglobulin A %K Immunoglobulin Fab Fragments %K Immunoglobulin Fc Fragments %K Male %K Models, Molecular %K Protein Aggregation, Pathological %K Protein Structure, Quaternary %X Native IgA1, for which no crystal structure is known, contains an O-galactosylated 23-residue hinge region that joins its Fab and Fc regions. IgA nephropathy (IgAN) is a leading cause of chronic kidney disease in developed countries. Because IgA1 in IgAN often has a poorly O-galactosylated hinge region, the solution structures of monomeric IgA1 from a healthy subject and three IgAN patients with four different O-galactosylation levels were studied. Analytical ultracentrifugation showed that all four IgA1 samples were monomeric with similar sedimentation coefficients, s(0)20,w. X-ray scattering showed that the radius of gyration (Rg) slightly increased with IgA1 concentration, indicating self-association, although their distance distribution curves, P(r), were unchanged with concentration. Neutron scattering indicated similar Rg values and P(r) curves, although IgA1 showed a propensity to aggregate in heavy water buffer. A new atomistic modelling procedure based on comparisons with 177000 conformationally-randomized IgA1 structures with the individual experimental scattering curves revealed similar extended Y-shaped solution structures for all four differentially-glycosylated IgA1 molecules. The final models indicated that the N-glycans at Asn(263) were folded back against the Fc surface, the C-terminal tailpiece conformations were undefined and hinge O-galactosylation had little effect on the solution structure. The solution structures for full-length IgA1 showed extended hinges and the Fab and Fc regions were positioned asymmetrically to provide ample space for the functionally-important binding of two FcαR receptors to its Fc region. Whereas no link between O-galactosylation and the IgA1 solution structure was detected, an increase in IgA1 aggregation with reduced O-galactosylation may relate to IgAN. %I University of Leicester