The gene and cDNA for the human high affinity immunoglobulin E receptor β chain and expression of the complete human receptor

The high affinity IgE receptor (FcεRI) is a tetrameric hetero-oligomer composed of an α chain, a β chain, and two disulfide-linked γ chains. The β chain contains four transmembrane (TM) segments and long cytoplasmic domains that are thought to play an important role in intracellular signaling. We now report the structural characterization and the sequence of the complete human β gene and cDNA. The gene spans ~10 kilobases and contains seven exons. There is a single transcription initiation site preceded by a TATA box. The first exon codes for the 5'-untranslated region and a portion of the N-terminal cytoplasmic tail. TM-1 is encoded in exons 2 and 3, TM-2 in exons 3 and 4, TM-3 in exon 5, and TM-4 in exon 6. The seventh and final exon encodes the end of the C-terminal cytoplasmic tail and the 3'- untranslated sequence. The human β gene appears to be a single copy gene. Two corresponding transcripts, detected as a doublet around 3.9 kilobases, are present in cells of mast cell and basophil lineage from different individuals, but not in the other hematopoietic cells tested here. The human β protein is homologous to rodent β. The consensus amino acid sequences of human, mouse, and rat β show 69% identical residues. Analysis of the surface expression of transfected receptors indicates that human αγ and αβγ complexes are expressed with comparable efficiency. Human β interacts with human α more efficiently than does rat β, and both rat and mouse β interact with their corresponding α more efficiently than does human β, demonstrating a species specificity of the α/β interaction.