cd05072: PTKc_Lyn (this model, PSSM-Id:173641 is obsolete and has been replaced by 270657)
Catalytic domain of the Protein Tyrosine Kinase, Lyn
Protein Tyrosine Kinase (PTK) family; Lyn kinase; catalytic (c) domain. The PTKc family is part of a larger superfamily that includes the catalytic domains of other kinases such as protein serine/threonine kinases, RIO kinases, and phosphoinositide 3-kinase (PI3K). PTKs catalyze the transfer of the gamma-phosphoryl group from ATP to tyrosine (tyr) residues in protein substrates. Lyn is a member of the Src subfamily of proteins, which are cytoplasmic (or non-receptor) tyr kinases. Src kinases contain an N-terminal SH4 domain with a myristoylation site, followed by SH3 and SH2 domains, a tyr kinase domain, and a regulatory C-terminal region containing a conserved tyr. They are activated by autophosphorylation at the tyr kinase domain, but are negatively regulated by phosphorylation at the C-terminal tyr by Csk (C-terminal Src Kinase). Src proteins are involved in signaling pathways that regulate cytokine and growth factor responses, cytoskeleton dynamics, cell proliferation, survival, and differentiation. Lyn is expressed in B lymphocytes and myeloid cells. It exhibits both positive and negative regulatory roles in B cell receptor (BCR) signaling. Lyn, as well as Fyn and Blk, promotes B cell activation by phosphorylating ITAMs (immunoreceptor tyr activation motifs) in CD19 and in Ig components of BCR. It negatively regulates signaling by its unique ability to phosphorylate ITIMs (immunoreceptor tyr inhibition motifs) in cell surface receptors like CD22 and CD5. Lyn also plays an important role in G-CSF receptor signaling by phosphorylating a variety of adaptor molecules.
Comment:Based on the structures of other PTK family members bound to substrate peptides and ATP analogs including, structures of human human Hck, Fyn and c-Src tyr kinases bound with inhibitors and ATP analogs.
Jiyao W et al.(2023). "The conserved domain database in 2023.",