Characterization of domains of herpes simplex virus type 1 glycoprotein E involved in Fc binding activity for immunoglobulin G aggregates.
Herpes simplex virus type 1 glycoproteins gE and gI form receptors for the Fc domain of immunoglobulin G (IgG) which are expressed on the surface of infected cells and on the virion envelope and which protect the virus from immune attack. Glycoprotein gE-1 is a low-affinity Fc receptor (FcR) that binds IgG aggregates, while gE-1 and gI-1 form a complex which serves as a higher-affinity FcR capable of binding IgG monomers. In this study, we describe two approaches used to map an Fc binding domain on gE-1 for IgG aggregates. First, we constructed nine plasmids encoding gE-1/gD-1 fusions proteins, each containing a large gE-1 peptide inserted into the ectodomain of gD-1. Fusion proteins were tested for FcR activity with IgG-sensitized erythrocytes in a rosetting assay. Three of the fusion proteins containing overlapping gE-1 peptides demonstrated FcR activity; the smallest peptide that retained Fc binding activity includes gE-1 amino acids 183 to 402. These results indicate that an Fc binding domain is located between gE-1 amino acids 183 and 402. To more precisely map the Fc binding domain, we tested a panel of 21 gE-1 linker insertion mutants. Ten mutants with insertions between gE-1 amino acids 235 and 380 failed to bind IgG-sensitized erythrocytes, while each of the remaining mutants demonstrated wild-type Fc binding activity. Taken together, these results indicate that the region of gE-1 between amino acids 235 and 380 forms an FcR domain. A computer-assisted analysis of the amino acid sequence of gE-1 demonstrates an immunoglobulin-like domain contained within this region (residues 322 to 359) which shares homology with mammalian FcRs.
Dubin
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Department of Medicine, School of Medicine, University of Pennsylvania, Philadelphia 19104-6073.
Basu
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Mallory
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Basu
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Tal-Singer
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Friedman
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D000595:Amino Acid Sequence; D000911:Antibodies, Monoclonal; D000914:Antibodies, Viral; D001483:Base Sequence; D002462:Cell Membrane / Q000378:metabolism; D004252:DNA Mutational Analysis; D000939:Epitopes; D018259:Herpesvirus 1, Human / Q000235:genetics / Q000276:immunology*; D007141:Immunoglobulin Fc Fragments / Q000378:metabolism*; D007074:Immunoglobulin G / Q000378:metabolism*; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D011485:Protein Binding; D011961:Receptors, Fc / Q000235:genetics / Q000378:metabolism; D011971:Receptors, Immunologic; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012635:Secretory Component / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D014759:Viral Envelope Proteins / Q000235:genetics / Q000378:metabolism*
D000911:Antibodies, Monoclonal; D000914:Antibodies, Viral; D000939:Epitopes; D007141:Immunoglobulin Fc Fragments; D007074:Immunoglobulin G; D011961:Receptors, Fc; D011971:Receptors, Immunologic; D011993:Recombinant Fusion Proteins; D012635:Secretory Component; D014759:Viral Envelope Proteins; C039447:glycoprotein D, Human herpesvirus 1; C044768:glycoprotein E, herpes simplex virus type 1; C044411:polymeric IgG