ITK: Proteins and Enzymes

Emtk/Itk/Tsk is a member of the Tec family of Protein Tyrosine Kinase (PTK) expressed in T, NK, and mast cells (1). Structurally, Emtk/Itk/Tsk possesses a tyrosine kinase (TK), a pleckstrin homology (PH) and a TEC homology domain. It also contains both SRC homology 2 (SH2) and a SRC homology 3 (SH3) domains (2). It lacks as well the amino-terminal myristylation signal and the negative autoregulatory phosphorylation site present in all members of the Src family of PTKs (3). Additionally, the Src tyrosine kinase LCK is required for Emtk/Itk/Tsk activation and recruitment by CD28 (4).