Description_x000D_ Biochem/physiol Actions_x000D_ TOPK is a MAPK kinase that phosphorylates p38 MAPK and is activated in a cell-cycle-dependent manner in neuronal progenitor cells in vitro. Expression of TOPK is detected in male germ line progenitor cells, activated T-cells, and a variety of lymphomas and leukemias. In vitro studies have shown that activated TOPK phosphorylated p38MAPK but not JNK or ERK. TOPK activation requires phosphorylation by both the M-phase CDK1/CyclinB kinase complex and another unknown kinase, possibly RafC or RafA. TOPK may play an important role in linking extracellular signals to an intracellular state, possibly allowing extracellular influence on the cell-cycle-related processes of proliferation or differentiation._x000D_ Physical form_x000D_ Supplied in 50 mM Tris-HCl, pH 7.5, with 150 mM NaCl, 0.25 mM DTT, 0.1 mM EGTA, 0.1 mM EDTA, 0.1 mM PMSF, and 25% glycerol._x000D_ Legal Information_x000D_ PRECISIO is a registered trademark of Sigma-Aldrich Co. LLC