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

The high affinity IgE receptor (Fc epsilon RI) is a tetrameric hetero-oligomer composed of an alpha chain, a beta chain, and two disulfide-linked gamma chains. The beta 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 beta gene and cDNA. The gene spans approximately 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 beta 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 beta protein is homologous to rodent beta. The consensus amino acid sequences of human, mouse, and rat beta show 69% identical residues. Analysis of the surface expression of transfected receptors indicates that human alpha gamma and alpha beta gamma complexes are expressed with comparable efficiency. Human beta interacts with human alpha more efficiently than does rat beta, and both rat and mouse beta interact with their corresponding alpha more efficiently than does human beta, demonstrating a species specificity of the alpha/beta interaction.