In ZAP-70 there are multiple phosphorylation sites (Y292, Y315, Y319, Y492, Y493) which have both positive and negative regulatory effect on its catalytic activity. Tyrosine 493 is a conserved regulatory site found within the activation loop of the kinase domain. This site has shown to be a positive regulatory site required for ZAP-70 kinase activity and is phosphorylated by Lck. This phosphorylation contribute to the active conformation of the catalytic domain.
|Antigen-bearing MHC Class II :TCR complex:CD4: Lck phosphorylated at Tyr394||protein tyrosine kinase activity (0004713)|
|8520027||The Syk/ZAP-70 protein tyrosine kinase connection to antigen receptor signalling processes||Semin Immunol||1995|
|9850860||The Syk family of protein tyrosine kinases in T-cell activation and development||Immunol Rev||1998|