Schematic representation of the functional domains of BTK. Kinase: this domain is responsible for activation of the BTK protein. This region hosts the binding sites for BTK inhibitors as depicted in this graphic.⁸⁹ PH, pleckstrin homology domain. This domain binds to phosphatidylinositol lipids which aids recruitment of proteins to the cellular membrane; SH, SRC homology domains. SH2 and SH3 are involved in protein-protein interactions and bind to phosphorylated tyrosines and proline regions, respectively. TH, TEC homology domain. This domain contains a proline rich region and is involved in protein-protein interactions.