TTK (Dual specificity Thr/Tyr kinase; also PYT and hMps1) is a 97-105 kDa member of the Ser/Thr protein kinase family of enzymes. It is expressed in rapidly proliferating tissues and cell lines, and participates in cell cycle regulation. In particular, it directs chromosome alignment, centrosome duplication, and spindle assembly checkpoint formation. Via phosphorylation, TTK is known to regulate p53, CDCA8 and TACC2. Human TTK is 857 amino acids (aa) in length and contains one protein kinase domain (aa 525-791). Activation occurs following homodimerization and autophosphorylation on Thr675, Thr676 and Thr686.