Antigen:BCR Antigen:p-BCR Phosphorylation of ITAMs of Ig-alpha (CD79A) and Ig-beta (CD79B) Authored: May, B, 2010-09-28 EC Number: 2.7.10 Edited: May, B, 2010-09-28 Pubmed12453414 Pubmed1702903 Pubmed7524079 Pubmed7592958 Pubmed7688784 Pubmed7927516 Pubmed8306975 Reactome Database ID Release 43983709 Reactome, http://www.reactome.org ReactomeREACT_118716 Reviewed: Wienands, J, 2012-02-11 The B cell receptor (BCR) comprises an immunoglobulin complexed with a heterodimer of Ig-alpha (CD79A, MB-1) and Ig-beta (CD79B, B29). After immunoglobulin IgM or IgD binds antigen the associated Ig-alpha and Ig-beta are each observed to be phosphorylated at two tyrosine residues in the cytoplasmic immunoreceptor tyrosine-activated motif (ITAM) (Sanchez et al. 1993, Hata et al. 1994, Saouaf et al. 1994, Saouaf et al. 1995). Saouaf et al. (1995) showed that the kinase Blk could phosphorylate both tyrosines of each ITAM and that the kinase SYK specifically bound phosphorylated but not unphosphorylated ITAMs. In mouse the kinase Lyn and other kinases phosphorylate one tyrosine and Syk is believed to phosphorylate the other (Yamanashi et al. 1991, Flaswinkel and Reth 1994, Rolli et al. 2002). has a Stoichiometric coefficient of 4