TXK is a member of the Tec family, which is a group of nonreceptor tyrosine kinases containing Src homology protein interaction domains (SH3, SH2) N-terminal to the catalytic tyr kinase domain. It also contains an N-terminal cysteine-rich region. TXK forms a complex with EF-1alpha and PARP1 that regulates interferon-gamma gene transcription in Th1 cells []. This entry represents the SH3 domain of TXK.
Txk is a member of the Tec protein tyrosine kinase family. It plays a role in TCR signal transduction, T cell development, and selection which is analogous to the function of Itk. Txk has been shown to interact with IFN-gamma [, ]. Unlike most of the Tec family members Txk lacks a PH domain. Instead Txk has a unique region containing a palmitoylated cysteine string which has a similar membrane tethering function as the PH domain []. This entry includes the SH2 domain of Txk.The Tec protein tyrosine kinase family includes Tec,Btk, Itk, Bmx, and Txk. They contain an NH2-terminal pleckstrin homology (PH) domain (absent in Txk), a proline-rich region, Src-homology 3 (SH3) and SH2 domains, and a COOH-terminal PTK domain. The TH domain consists of a Zn2+-binding Btk motif and a proline-rich region. The Btk motif is found in Tec kinases, Ras GAP, and IGBP and crucial to the function of the PH domain. It is not present in Txk which is not surprising since it lacks a PH domain. The type 1 splice form of the Drosophila homologue also lacks both the PH domain and the Btk motif. The proline-rich regions are highly conserved for the most part with the exception of Bmx whose residues surrounding the PXXP motif are not conserved (TH-like) and Btk29A which is entirely unique with large numbers of glycine residues (TH-extended). Tec family members all lack a C-terminal tyrosine having an autoinhibitory function in its phosphorylated state [, ].
