Tyrosine kinase Lyn
| Tyrosine kinase Lyn | ||
|---|---|---|
| Properties of human protein | ||
| Mass / length primary structure | 511 amino acids | |
| Isoforms | LYN A, LYN B | |
| Identifier | ||
| Gene name | LYN | |
| External IDs | ||
| Enzyme classification | ||
| EC, category | 2.7.10.2 , tyrosine kinase | |
| Response type | Phosphorylation of tyrosine residues | |
| Substrate | ATP + protein tyrosine | |
| Products | ADP + protein tyrosine phosphate | |
| Occurrence | ||
| Parent taxon | Vertebrates | |
| Orthologue | ||
| human | House mouse | |
| Entrez | 4067 | 17096 |
| Ensemble | ENSG00000254087 | ENSMUSG00000042228 |
| UniProt | P07948 | P25911 |
| Refseq (mRNA) | NM_001111097 | NM_001111096 |
| Refseq (protein) | NP_001104567 | NP_001104566 |
| Gene locus | Chr 8: 55.88 - 56.01 Mb | Chr 4: 3.68 - 3.79 Mb |
| PubMed search | 4067 |
17096
|
The tyrosine kinase Lyn is an enzyme in the cytosol of vertebrate cells , including the B cells of the immune system and several other cell types . Lyn catalyzes the phosphorylation of tyrosine , which is built into proteins. The proteins modified in this way change their state of activity or their function. These reactions are part of a large number of signal cascades that influence gene expression in the corresponding cells and thus their further behavior. Lyn is involved in the infection with the herpes virus saimiri in squirrel monkeys .
Function in B cells
It is a Src kinase that is present in B cells and mediates the signaling of the B cell receptor. Activated Lyn phosphorylates ITAMs in the intracellular domains of the B-cell receptor- associated chains Ig-alpha and Ig-beta. The kinase Syk , which is extremely important for the B-cell receptor signal, can then bind to these phosphorylated motifs .
Activation of Lyn
Lyn has several distinctive protein domains, including an SH3 domain, an SH2 domain and a kinase domain. Two tyrosines in Lyn can be phosphorylated, which regulates the activity of the kinase. Phosphorylation of a tyrosine (Tyr527) at the C-terminal end of the protein causes the protein to collapse and become inactive. Only when this tyrosine is unphosphorylated is the kinase in a functional conformation. This phosphorylation is mediated by phosphatases like CD45 and CD148 , which favor the active conformation, and kinases like Csk and Chk, which favor the inactive form. The phosphorylation of Tyr 527 is therefore important for the potential activation of Lyn. But it is only through the phosphorylation of another tyrosine (Tyr 416) in the kinase domain that Lyn becomes really active. This second tyrosine residue is phosphorylated by neighboring Src kinases such as Fyn , Blk or another Lyn molecule. This happens preferentially when B-cell receptors and thus the associated Src kinases aggregate through antigen binding. A cross-linking of the B-cell receptors triggers the activation of Src kinases such as Lyn.
Individual evidence
- ↑ Orthologist at OMA
- ↑ UniProt P07948
- ↑ Kurosaki T, Hikida M: Tyrosine kinases and their substrates in B lymphocytes . In: Immunol. Rev. . 228, No. 1, March 2009, pp. 132-48. doi : 10.1111 / j.1600-065X.2008.00748.x . PMID 19290925 .