Monomeric and oligomeric complexes of the B cell antigen receptor.
The current structural model of the B cell antigen receptor (BCR) describes it as a symmetric protein complex in which one membrane-bound immunoglobulin molecule (mIg) is noncovalently bound on each side by an Ig-alpha/Ig-beta heterodimer. Using peptide-tagged Ig-alpha proteins, blue native polyacrylamide gel electrophoresis (BN-PAGE), and biosynthetical labeling of B cells, we find that the mIg:Ig-alpha/Ig-beta complex has a stoichiometry of 1:1 and not 1:2. An anti-Flag stimulation of B cells coexpressing Flag-tagged and wild-type Ig-alpha proteins results in the phosphorylation of both Ig-alpha proteins, suggesting that on the surface of living B cells, several BCR monomers are in contact with each other. A BN-PAGE analysis after limited detergent lysis provides further evidence for an oligomeric BCR structure.
Department of Molecular Immunology, University of Freiburg and Max Planck Institute for Immunobiology, Germany.
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D000818:Animals; D015703:Antigens, CD / Q000235:genetics / Q000276:immunology*; D051925:CD79 Antigens; D002460:Cell Line; D004072:Digitonin; D004591:Electrophoresis, Polyacrylamide Gel / Q000379:methods; D007072:Immunoglobulin D / Q000276:immunology; D007075:Immunoglobulin M / Q000276:immunology; D007202:Indicators and Reagents; D051379:Mice; D010766:Phosphorylation; D011947:Receptors, Antigen, B-Cell / Q000235:genetics / Q000276:immunology*; D012995:Solubility
D015703:Antigens, CD; D051925:CD79 Antigens; C497882:Cd79a protein, mouse; C497884:Cd79b protein, mouse; D007072:Immunoglobulin D; D007075:Immunoglobulin M; D007202:Indicators and Reagents; D011947:Receptors, Antigen, B-Cell; D004072:Digitonin