Catalytic domain of Ste20-Like Kinase-like Serine/Threonine Kinases
STKs catalyze the transfer of the gamma-phosphoryl group from ATP to serine/threonine residues on protein substrates. Members of the subfamily include SLK, STK10 (also called LOK for Lymphocyte-Oriented Kinase), SmSLK (Schistosoma mansoni SLK), and related proteins. SLK promotes apoptosis through apoptosis signal-regulating kinase 1 (ASK1) and the mitogen-activated protein kinase (MAPK) p38. It also plays a role in mediating actin reorganization. STK10 is responsible in regulating the CD28 responsive element in T cells, as well as leukocyte function associated antigen (LFA-1)-mediated lymphocyte adhesion. SmSLK is capable of activating the MAPK Jun N-terminal kinase (JNK) pathway in human embryonic kidney cells as well as in Xenopus oocytes. It may participate in regulating MAPK cascades during host-parasite interactions. The SLK-like subfamily is part of a larger superfamily that includes the catalytic domains of other STKs, protein tyrosine kinases, RIO kinases, aminoglycoside phosphotransferase, choline kinase, and phosphoinositide 3-kinase.