Catalytic domain of the Serine/Threonine Kinase, Mammalian Ste20-like protein kinase 4
STKs catalyze the transfer of the gamma-phosphoryl group from ATP to serine/threonine residues on protein substrates. MST4 is sometimes referred to as MASK (MST3 and SOK1-related kinase). It plays a role in mitogen-activated protein kinase (MAPK) signaling during cytoskeletal rearrangement, morphogenesis, and apoptosis. It influences cell growth and transformation by modulating the extracellular signal-regulated kinase (ERK) pathway. MST4 may also play a role in tumor formation and progression. It localizes in the Golgi apparatus by interacting with the Golgi matrix protein GM130 and may play a role in cell migration. The MST4 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.