Bruton's tyrosine kinase
| Bruton's tyrosine kinase | ||
|---|---|---|
|
||
| Belt model from BTK | ||
| Properties of human protein | ||
| Mass / length primary structure | 658 amino acids | |
| Cofactor | Zn 2+ | |
| Identifier | ||
| Gene name | BTK | |
| External IDs | ||
| Enzyme classification | ||
| EC, category | 2.7.10.2 , tyrosine kinase | |
| Response type | Phosphorylation | |
| Substrate | GTF2I, SH3BP5, IBTK | |
| Occurrence | ||
| Parent taxon | Vertebrates | |
Bruton's tyrosine kinase (BTK) is an enzyme found in vertebrates that catalyzes the phosphorylation of certain proteins . It is therefore a kinase . It belongs to the tyrosine kinases of the Tec family , which is mainly expressed in B cells . BTK takes on important functions in conveying the B-cell receptor signal to the inside of the cell. A mutation in the BTK gene in humans is the cause of the so-called Bruton's syndrome ( XLA ).
construction
The Bruton tyrosine kinase consists of a PH domain at the N-terminus, followed by a TH ( Tec homology ) domain, an SH3 domain, an SH2 domain and a C-terminal kinase domain. The TH domain in turn consists of a BH domain ( Btk homology ) and one or two proline-rich regions.
activation
The first step in activating Btk is recruitment to the plasma membrane through the PH domain, which binds to phosphatidylinostiol-3,4,5-trisphosphate (PIP 3 ). PIP 3 is a product of the PI3 kinase . At the same time, the adapter protein BLNK is important for the recruitment of Btk to the membrane and thus to the B cell receptor. The activity of Btk in B cells presumably depends on the kinases Syk and Lyn .
function
An important function of Btk is the activation of the PLCγ2. Btk phosphorylates the tyrosines 753 and 759 in PLCγ2, which activates them. In addition, Btk recruits phosphatidylinositol-4-phosphate 5 kinase (PIP5K) to the plasma membrane. PIP5K in turn synthesizes the important PLCγ2 substrate phosphatitylinsitol-4,5-bisphosphate (PIP 2 ) from PIP.
A point mutation in Btk in mice means that the kinase is not directed to the plasma membrane. These mice are called Xid ( X-linked immunodeficient ) mice .
Individual evidence
- ↑ Orhologist at OMA
- ↑ a b 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 .