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Catalytic domain of the Protein Tyrosine Kinase, Zeta-chain-associated protein of 70kDa PTKs catalyze the transfer of the gamma-phosphoryl group from ATP to tyrosine (tyr) residues in protein substrates. Zap-70 is a cytoplasmic (or nonreceptor) PTK containing two Src homology 2 (SH2) domains N-terminal to the catalytic tyr kinase domain. Zap-70 is primarily expressed in T-cells and NK cells, and is a crucial component in T-cell receptor (TCR) signaling. Zap-70 binds the phosphorylated ITAM (immunoreceptor tyr activation motif) sequences of the activated TCR zeta-chain through its SH2 domains, leading to its phosphorylation and activation. It then phosphorylates target proteins, which propagate the signals to downstream pathways. Zap-70 is hardly detected in normal peripheral B-cells, but is present in some B-cell malignancies. It is used as a diagnostic marker for chronic lymphocytic leukemia (CLL) as it is associated with the more aggressive subtype of the disease. The Zap-70 subfamily is part of a larger superfamily that includes the catalytic domains of other kinases such as protein serine/threonine kinases, RIO kinases, aminoglycoside phosphotransferase, choline kinase, and phosphoinositide 3-kinase. |
Jiyao W et al.(2023). "The conserved domain database in 2023.",