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HUMAN FC GAMMA RECEPTOR IIB ECTODOMAIN (CD32)
Structural highlights
DiseaseFCG2B_HUMAN Note=A chromosomal aberration involving FCGR2B is found in a follicular lymphoma. Translocation t(1;22)(q22;q11). The translocation leads to the hyperexpression of the receptor. This may play a role in the tumor progression. Defects in FCGR2B are a cause of susceptibility to systemic lupus erythematosus (SLE) [MIM:152700. A chronic, relapsing, inflammatory, and often febrile multisystemic disorder of connective tissue, characterized principally by involvement of the skin, joints, kidneys and serosal membranes. It is of unknown etiology, but is thought to represent a failure of the regulatory mechanisms of the autoimmune system. The disease is marked by a wide range of system dysfunctions, an elevated erythrocyte sedimentation rate, and the formation of LE cells in the blood or bone marrow.[1] [2] FunctionFCG2B_HUMAN Receptor for the Fc region of complexed or aggregated immunoglobulins gamma. Low affinity receptor. Involved in a variety of effector and regulatory functions such as phagocytosis of immune complexes and modulation of antibody production by B-cells. Binding to this receptor results in down-modulation of previous state of cell activation triggered via antigen receptors on B-cells (BCR), T-cells (TCR) or via another Fc receptor. Isoform IIB1 fails to mediate endocytosis or phagocytosis. Isoform IIB2 does not trigger phagocytosis. Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedFcgamma-receptors (FcgammaRs) represent the link between the humoral and cellular immune responses. Via the binding to FcgammaR-positive cells, immunocomplexes trigger several functions such as endocytosis, antibody-dependent cell-mediated cytotoxity (ADCC) and the release of mediators, making them a valuable target for the modulation of the immune system. We solved the crystal structure of the soluble human Fcgamma-receptor IIb (sFcgammaRIIb) to 1.7 A resolution. The structure reveals two typical immunoglobulin (Ig)-like domains enclosing an angle of approximately 70 degrees, leading to a heart-shaped overall structure. In contrast to the observed flexible arrangement of the domains in other members of the Ig superfamily, the two domains are anchored by several hydrogen bonds. The structure reveals that the residues relevant for IgG binding, which were already partially characterized by mutagenesis studies, are located within the BC, C'E and FG loops between the beta-strands of the second domain. Moreover, we discuss a model for the sFcgammaRIIb:IgG complex. In this model, two FcgammaR molecules bind one IgG molecule with their second domains, while the first domain points away from the complex and is therefore available for binding other cell surface molecules, by which potential immunosuppressing functions could be mediated. Crystal structure of the soluble form of the human fcgamma-receptor IIb: a new member of the immunoglobulin superfamily at 1.7 A resolution.,Sondermann P, Huber R, Jacob U EMBO J. 1999 Mar 1;18(5):1095-103. PMID:10064577[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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