Catalytic domain of the Protein Tyrosine Kinases, Tyrosine kinase expressed in hepatocellular carcinoma and Resting lymphocyte kinase
PTKs catalyze the transfer of the gamma-phosphoryl group from ATP to tyrosine (tyr) residues in protein substrates. Tec and Rlk (also named Txk) are members of the Tec-like subfamily of proteins, which are cytoplasmic (or nonreceptor) PTKs with similarity to Src kinases in that they contain Src homology protein interaction domains (SH3, SH2) N-terminal to the catalytic tyr kinase domain. Unlike Src kinases, most Tec subfamily members except Rlk also contain an N-terminal pleckstrin homology (PH) domain, which binds the products of PI3K and allows membrane recruitment and activation. Instead of PH, Rlk contains an N-terminal cysteine-rich region. In addition to PH, Tec also contains the Tec homology (TH) domain with proline-rich and zinc-binding regions. Tec kinases are expressed mainly by haematopoietic cells. Tec is more widely-expressed than other Tec-like subfamily kinases. It is found in endothelial cells, both B- and T-cells, and a variety of myeloid cells including mast cells, erythroid cells, platelets, macrophages and neutrophils. Rlk is expressed in T-cells and mast cell lines. Tec and Rlk are both key components of T-cell receptor (TCR) signaling. They are important in TCR-stimulated proliferation, IL-2 production and phopholipase C-gamma1 activation. The Tec/Rlk 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.
Comment:includes ATP binding and substrate binding sites
Comment:Based on the structures of other PTK family members bound to substrate peptides and ATP analogs, as well as the structures of human Itk and Btk bound with inhibitors.
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