[HTML][HTML] Crystal structure of the HSV-1 Fc receptor bound to Fc reveals a mechanism for antibody bipolar bridging

ER Sprague, C Wang, D Baker, PJ Bjorkman - PLoS biology, 2006 - journals.plos.org
ER Sprague, C Wang, D Baker, PJ Bjorkman
PLoS biology, 2006journals.plos.org
Herpes simplex virus type-1 expresses a heterodimeric Fc receptor, gE-gI, on the surfaces of
virions and infected cells that binds the Fc region of host immunoglobulin G and is
implicated in the cell-to-cell spread of virus. gE-gI binds immunoglobulin G at the basic pH of
the cell surface and releases it at the acidic pH of lysosomes, consistent with a role in
facilitating the degradation of antiviral antibodies. Here we identify the C-terminal domain of
the gE ectodomain (CgE) as the minimal Fc-binding domain and present a 1.78-Å CgE …
Herpes simplex virus type-1 expresses a heterodimeric Fc receptor, gE-gI, on the surfaces of virions and infected cells that binds the Fc region of host immunoglobulin G and is implicated in the cell-to-cell spread of virus. gE-gI binds immunoglobulin G at the basic pH of the cell surface and releases it at the acidic pH of lysosomes, consistent with a role in facilitating the degradation of antiviral antibodies. Here we identify the C-terminal domain of the gE ectodomain (CgE) as the minimal Fc-binding domain and present a 1.78-Å CgE structure. A 5-Å gE-gI/Fc crystal structure, which was independently verified by a theoretical prediction method, reveals that CgE binds Fc at the CH2-CH3 interface, the binding site for several mammalian and bacterial Fc-binding proteins. The structure identifies interface histidines that may confer pH-dependent binding and regions of CgE implicated in cell-to-cell spread of virus. The ternary organization of the gE-gI/Fc complex is compatible with antibody bipolar bridging, which can interfere with the antiviral immune response.
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