Interleukin-2 tyrosine kinase (Itk) is a non-receptor tyrosine kinase of the Tec family that is activated upon antigen binding to the T cell receptor (Schwartzberg et al. 2005; Berg 2007). Itk is comprised of four regulatory domains: PH (Pleckstrin homology), TH (Tec homology), SH3, SH2 and the catalytic kinase domain. SH3 domains share a common fold consisting of five anti-parallel β strands that form a β barrel and bind canonical proline rich ligands as well as a variety of noncanonical ligands (Agrawal and Kishan 2002).