Antigen-bearing MHC Class II: TCR with phosphorylated ITAMs:CD4 Antigen-bearing MHC Class II :TCR complex:CD4: Lck phosphorylated at Tyr394 Phosphorylation of ITAM motifs in CD3 complexes Authored: Rudd, C.E., de Bono, B, Garapati, P V, 2008-01-24 15:53:10 EC Number: 2.7.10 Pubmed15084594 Pubmed16364187 Reactome Database ID Release 43202165 Reactome, http://www.reactome.org ReactomeREACT_12633 Reviewed: Trowsdale, J, 2008-02-26 12:02:59 The autophosphorylated, active Lck is now proximally positioned to phosphorylate specific tyrosine residues within ITAMs (immunoreceptor tyrosine-based activation motifs) located within the CD3 and the TCR zeta signaling chains of the TCR. ITAMs consist of evolutionarily conserved amino-acid sequence motifs of D/ExYxxLx(6-8)YxxL. Both the tyrosine residues in the motif are phosphorylated by Lck and the TCR complex include 10 ITAMs with one ITAM in each of the CD3 chains including the three tandem ITAMs in each zeta chains. has a Stoichiometric coefficient of 20