Oxidant stress-activated serine/threonine kinase that may play a role in the response to environmental stress. Targets to the Golgi apparatus where it appears to regulate protein transport events, cell adhesion, and polarity complexes important for cell migration (By similarity). ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] Interaction with Golgi matrix protein GOLGA2 leads to autophosphorylation on Thr-174, possibly as a consequence of stabilization of dimer formation. The C-terminal non-catalytic region inhibits the kinase activity (By similarity). Homodimer. Interacts with CTTNBP2NL. Localizes to the Golgi apparatus. Belongs to the protein kinase superfamily. STE Ser/Thr protein kinase family. STE20 subfamily.