5o4e
From Proteopedia
Crystal structure of VEGF in complex with heterodimeric Fcab JanusCT6
Structural highlights
FunctionIGG1_HUMAN Immunoglobulins, also known as antibodies, are membrane-bound or secreted glycoproteins produced by B lymphocytes. In the recognition phase of humoral immunity, the membrane-bound immunoglobulins serve as receptors which, upon binding of a specific antigen, trigger the clonal expansion and differentiation of B lymphocytes into immunoglobulins-secreting plasma cells. Secreted immunoglobulins mediate the effector phase of humoral immunity, which results in the elimination of bound antigens (PubMed:22158414, PubMed:20176268). The antigen binding site is formed by the variable domain of one heavy chain, together with that of its associated light chain. Thus, each immunoglobulin has two antigen binding sites with remarkable affinity for a particular antigen. The variable domains are assembled by a process called V-(D)-J rearrangement and can then be subjected to somatic hypermutations which, after exposure to antigen and selection, allow affinity maturation for a particular antigen (PubMed:20176268, PubMed:17576170).[1] [2] [3] Publication Abstract from PubMedFcabs (Fc domain with antigen-binding sites) are promising novel therapeutics. By engineering of the C-terminal loops of the CH3 domains, two antigen binding sites can be inserted in close proximity. In order to elucidate the binding mode(s) between homodimeric Fcabs and small homodimeric antigens, the interaction between the Fcabs 448 and CT6 (having the AB, CD and EF loops and the C-termini engineered) with homodimeric VEGF was investigated. The crystal structures of these Fcabs, which form polymers with the antigen VEGF in solution, were determined. However, construction of heterodimeric Fcabs (JanusFcabs: one chain Fc-wt, one chain VEGF-binding) results in formation of distinct JanusFcab-VEGF complexes (2:1), which allowed elucidation of the crystal structure of the JanusCT6-VEGF complex at 2.15 A resolution. VEGF binding to Janus448 and JanusCT6 is shown to be entropically unfavorable, but enthalpically favorable. Structure-function relationships are discussed with respect to Fcab design and engineering strategies. Two-Faced Fcab Prevents Polymerization with VEGF and Reveals Thermodynamics and the 2.15 A Crystal Structure of the Complex.,Lobner E, Humm AS, Mlynek G, Kubinger K, Kitzmuller M, Traxlmayr MW, Djinovic-Carugo K, Obinger C MAbs. 2017 Aug 17:0. doi: 10.1080/19420862.2017.1364825. PMID:28816592[4] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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