6g1e
BEAT Fc with improved heterodimerization (Q3A-D84.4Q)
Structural highlights
Disease[IGHG1_HUMAN] Defects in IGHG1 are a cause of multiple myeloma (MM) [MIM:254500]. MM is a malignant tumor of plasma cells usually arising in the bone marrow and characterized by diffuse involvement of the skeletal system, hyperglobulinemia, Bence-Jones proteinuria and anemia. Complications of multiple myeloma are bone pain, hypercalcemia, renal failure and spinal cord compression. The aberrant antibodies that are produced lead to impaired humoral immunity and patients have a high prevalence of infection. Amyloidosis may develop in some patients. Multiple myeloma is part of a spectrum of diseases ranging from monoclonal gammopathy of unknown significance (MGUS) to plasma cell leukemia. Note=A chromosomal aberration involving IGHG1 is found in multiple myeloma. Translocation t(11;14)(q13;q32) with the IgH locus. Translocation t(11;14)(q13;q32) with CCND1; translocation t(4;14)(p16.3;q32.3) with FGFR3; translocation t(6;14)(p25;q32) with IRF4. Function[IGG1_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 PubMedWe previously reported efficient heavy chain (Hc) assembly of heterodimeric bispecific antibodies (bsAbs) by exchanging the inter-domain protein interface of the human IgG1 CH3 dimer with the protein interface of the constant alpha (Ca) and beta (Cb) domains of the human T-cell receptor (TCR), a technology known as BEAT (Bispecific Engagement by Antibodies based on the T-cell receptor). Efficient heterodimerization in mammalian cell transient transfections was observed, but levels were influenced by the nature of the binding arms, particularly in the Fab-scFv-Fc format. In this study, we report a single amino acid change that significantly and consistently improved the heterodimerization rate of this format (>/=95%) by inducing partial disorder in one homodimer species without affecting the heterodimer. Correct folding and assembly of the heterodimer were confirmed by the high-resolution (1.88-1.98 A) crystal structure presented here. Thermal stability and 1-anilinonaphthalene-8-sulfonic acid (ANS)-binding experiments, comparing original BEAT, mutated BEAT and "knobs-into-holes" (KiH) interfaces, suggested a cooperative assembly process of Hcs in heterodimers. The observed gain in stability of the interfaces could be classified in the following rank order: mutated BEAT > original BEAT > KiH. We therefore propose that the superior cooperativity found in BEAT interfaces is the key driver of their greater performance. Furthermore, we show how the mutated BEAT interface can be exploited for the routine preparation of drug candidates, with minimal risk of homodimer contamination using a single Protein A chromatography step. A single mutation increases heavy chain heterodimer assembly of bispecific antibodies by inducing structural disorder in one homodimer species.,Stutz C, Blein S J Biol Chem. 2020 May 13. pii: RA119.012335. doi: 10.1074/jbc.RA119.012335. PMID:32404368[4] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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