title: Human mb-1 gene: complete cDNA sequence and its expression in B cells bearing membrane Ig of various isotypes.
abstract: The transmembrane protein, IgM-alpha, a product of mb-1 gene, has been shown to be specifically associated with membrane-bound IgM on the plasma membrane of B lymphocytes. Recent studies have suggested that IgM-alpha may play a role in transducing signals from the Ag receptors during the activation of B cells. A large amount of information has been obtained in the mouse system regarding IgM-alpha and other components of the newly conceived B cell Ag receptor complex. Here we report the cloning and the nucleotide sequencing of cDNA clones of human mb-1, covering the entire length of the mRNA. At the amino acid sequence level, human and murine mb-1 share a high homology in their transmembrane and intracytoplasmic segments, suggesting an important biologic function for these regions of mb-1. A major difference, mainly in the 3' untranslated part, exists between our cDNA sequence and the published partial human mb-1 cDNA sequence. It has also been observed that human mb-1 is expressed not only by B cell lines expressing membrane-bound Ig of mu and delta isotypes but also those expressing membrane-bound Ig of alpha and gamma isotypes.
authors.affiliation: Tanox Biosystems, Inc., Houston, TX 77025.
authors.forename: L M
authors.initials: LM
authors.lastname: Yu
authors.forename: T W
authors.initials: TW
authors.lastname: Chang
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D015703:Antigens, CD; D001402:B-Lymphocytes / Q000276:immunology*; D001483:Base Sequence; D051925:CD79 Antigens; D003001:Cloning, Molecular; D004247:DNA / Q000737:chemistry* / Q000302:isolation & purification; D006801:Humans; D007132:Immunoglobulin Isotypes / Q000032:analysis*; D008562:Membrane Glycoproteins / Q000032:analysis / Q000235:genetics*; D051379:Mice; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction; D011947:Receptors, Antigen, B-Cell / Q000032:analysis*
chemical_list: D015703:Antigens, CD; D051925:CD79 Antigens; C497881:CD79A protein, human; C497882:Cd79a protein, mouse; D007132:Immunoglobulin Isotypes; D008562:Membrane Glycoproteins; D011947:Receptors, Antigen, B-Cell; D004247:DNA