title: Direct identification of the putative surface IgM receptor-associated molecule encoded by murine B cell-specific mb-1 gene.
abstract: The B cell-specific mb-1 gene was recently reported to encode a putative surface glycoprotein with CD3-like structural properties. Hombach et al. suggested and presented evidence to show that this mb-1 gene encodes the 34-kDa membrane glycoprotein (B34 or IgM-alpha) associated with IgMR molecule. To identify the mb-1 gene product directly in B cells, affinity-purified MB-1-specific antibody was prepared by immunization of rabbits with synthetic MB-1 oligopeptide. Immunoprecipitation in combination with two-dimensional diagonal gel electrophoresis analysis revealed that this antibody detected a B cell-specific surface glycoprotein that is very similar to the IgM-alpha (B34) protein described by Hombach et al. However, MB-1 protein exists usually as the monomeric form on the surface of B cells, in contrast to IgM-alpha, which was detected as the dimeric (IgM-alpha/IgM-alpha or IgM-alpha/Ig-beta) protein. We also found that MB-1 protein is already expressed on the sIgM- pre-B cell lymphoma, which might suggest an alternative functional role of this B cell-specific MB-1 protein in B cell differentiation. The molecular identity of MB-1 protein and IgM-alpha (B34) is discussed.
authors.affiliation: Department of Immunology, Saga Medical School, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Matsuo
authors.forename: M
authors.initials: M
authors.lastname: Kimoto
authors.forename: N
authors.initials: N
authors.lastname: Sakaguchi
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000918:Antibody Specificity; D015703:Antigens, CD; D001402:B-Lymphocytes / Q000166:cytology / Q000276:immunology*; D051925:CD79 Antigens; D002454:Cell Differentiation / Q000276:immunology; D002846:Chromatography, Affinity; D016393:Lymphoma, B-Cell; D008562:Membrane Glycoproteins / Q000032:analysis* / Q000235:genetics; D051379:Mice; D008969:Molecular Sequence Data; D008970:Molecular Weight; D011233:Precipitin Tests; D011947:Receptors, Antigen, B-Cell; D011961:Receptors, Fc / Q000378:metabolism*; D014407:Tumor Cells, Cultured
chemical_list: D015703:Antigens, CD; D051925:CD79 Antigens; C497882:Cd79a protein, mouse; D008562:Membrane Glycoproteins; D011947:Receptors, Antigen, B-Cell; D011961:Receptors, Fc; C035311:immunoglobulin M receptor