Identification of multiple isoforms of the low-affinity human IgG Fc receptor.
Two varieties of similar, but structurally distinct, cDNA clones for the human low-affinity receptors for the Fc portion of immunoglobulin G (Fc gamma RII) have been isolated. One type of clone was obtained from human B lymphocytes, and the other from PHA-activated peripheral T cells and monocytes. Transfection of both prototype clones into Cos-7 cells and subsequent specific staining with monoclonal antibodies of the CDw32 group confirmed the identification of the gene products. The nucleotide sequence of the cDNA clone from B lymphocytes contains an open reading frame that encodes a protein of relative mass (Mr) 27,000 with an extracellular domain of 179 amino acids containing three potential N-glycosylation sites, a 26 amino acid transmembrane domain, and a 44 amino acid cytoplasmic domain. The clones from peripheral T cells and monocytes both encoded a protein of Mr 31,000 with a 179 amino acid extracellular domain containing two potential N-glycosylation sites and a 26 amino acid transmembrane domain. The two types of clones had similar sequences in their immunoglobulin-like extracellular and transmembrane domain, but differed in their leader sequences and 3'untranslated regions. The most notable difference between the clones was the presence of a distinctive 76 amino acid cytoplasmic domain in those isolated from T cells and monocytes.
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Hospital for Joint Diseases, New York University Medical Center, NY 10003.
D000595:Amino Acid Sequence; D000818:Animals; D000943:Antigens, Differentiation / Q000235:genetics*; D001402:B-Lymphocytes / Q000502:physiology*; D001483:Base Sequence; D004247:DNA / Q000032:analysis*; D006801:Humans; D007074:Immunoglobulin G / Q000235:genetics; D051379:Mice; D008969:Molecular Sequence Data; D009000:Monocytes / Q000502:physiology*; D011961:Receptors, Fc / Q000235:genetics*; D017452:Receptors, IgG; D012689:Sequence Homology, Nucleic Acid; D013601:T-Lymphocytes / Q000502:physiology*
D000943:Antigens, Differentiation; D007074:Immunoglobulin G; D011961:Receptors, Fc; D017452:Receptors, IgG; D004247:DNA