Phosphorylation of the ITAMs by Lck is followed by the recruitment of the ZAP-70 a member of Syk family PTK, to the receptor complex. ZAP-70 is exclusively expressed in T cells and NK cells. The dually phosphorylated ITAMs provide a high-affinity docking site for the tandem SH2-domains of the ZAP-70. Once recruited, ZAP-70 is activated by phosphorylation and will be responsible for the phosphorylation of further downstream molecules. Due to the presence of 10 ITAMs in the TCR complex, up to 10 ZAP-70 molecules may cluster on the fully phosphorylated receptors.
Chu, DH, Morita, CT, Weiss, A
van Oers, NS, Weiss, A
Tasken, K, Mustelin, T
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