Biophysical characterization of dynamic structures of immunoglobulin G

Abstract

Immunoglobulin G (IgG) is a major antibody and functions as a hub linking specific antigen binding and recruitment of effector molecules typified by Fcγ receptors (FcγRs). These activities are associated primarily with interactions involving its Fab and Fc sites, respectively. An IgG molecule is characterized by a multiple domain modular structure with conserved N-glycosylation in Fc. The molecule displays significant freedom in internal motion on various spatiotemporal scales. The consequent conformational flexibility and plasticity of IgG glycoproteins are functionally significant and potentially important factors for design and engineering of antibodies with enhanced functionality. In this article, experimental and computational approaches are outlined for characterizing the conformational dynamics of IgG molecules in solution. In particular, the importance of integration of these approaches is highlighted, as illustrated by dynamic intramolecular interactions between the pair of N-glycans and their proximal amino acid residues in Fc. These interactions can critically affect effector functions mediated by human IgG1 and FcγRIII. Further improvements in individual biophysical techniques and their integration will advance understanding of dynamic behaviors of antibodies in physiological and pathological conditions. Such understanding will provide opportunities for engineering antibodies through controlling allosteric networks in IgG molecules.

Antibodies Inhibiting the Type III Secretion System of Gram-Negative Pathogenic Bacteria

“…There are five main isotypes of Abs found in humans: IgA, IgD, IgE, IgM and IgG. IgA and IgG are the most commonly used in therapeutics [25,27,28]. IgA are found in the mucosal membranes and help to prevent the colonization of mucosal pathogens.…”

“…They are commonly found as dimers that take the shape of two Y's bound together at the stem [27]. IgG are considered memory Abs and provide the main Ab-based immunity against pathogens and comprise approximately 80% of total pooled Abs within humans [28]. Some antibodies, such as IgD, are membrane-bound and involved in cellular signaling.…”

“…To date, there have been approximately 85 mAbs approved by the FDA for use as immunotherapy and 80 that have been approved by countries within the European Union [49]. Abs used as therapeutics are often administered via intravenous (IV) injections, intramuscularly, or parenterally [28,47]. The route of administration can be very important for the effectiveness of therapeutic Abs.…”

Rigid monoclonal antibodies improve detection of SARS-CoV-2 nucleocapsid protein

“…In contrast, the resolution of small-angle X-ray scattering (SAXS) is sufficient, especially when atomic structures of individual components are available, to determine the conformational variability of the antigen-binding fragments (Fabs) in various antibodies, 30 including complexes with antigens or Fc-gamma receptors (FcγRs). 31 , 32 A previous study showed that the Fabs’ conformational flexibility is derived from the inherent plasticity of the Fc-hinge regions in solution. 33 Rigidity of the hinges inversely correlates with, and can modulate mAb agonistic potency, 34 , 35 and this highlights the importance of newer strategies to modulate antibody-agglutination.…”

Rigid monoclonal antibodies improve detection of SARS-CoV-2 nucleocapsid protein

“…Although there have been several attempts by cryo-electron tomography ( Bongini et al, 2005 ; Jay et al, 2018 ; Lei et al, 2019 ; Sandin, Ofverstedt, Wikstrom, Wrange, & Skoglund, 2004 ), and negative stain electron tomography ( X. Zhang et al, 2015 ), large scale flexibility measurements are often not amenable to single-particle techniques. In contrast, the resolution of SAXS is sufficient (especially when atomic structures of individual components are available) to determine the Fab regions’ conformational variability in various antibodies, including complexes with antigens or Fc-gamma receptors (FcγRs) ( Wright, Elliston, Hui, & Perkins, 2019 ; Yanaka, Yogo, & Kato, 2020 ). A previous study showed that Fab regions’ conformational flexibility is derived from the Fc regions’ inherent plasticity in solution ( Remesh, Armstrong, Mahan, Luo, & Hammel, 2018 ).…”