Serine-threonine protein kinase which may be involved in maintenance of cell integrity. Functionally complements SLT2 null mutant in S.cerevisiae. ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] Activated by threonine and tyrosine phosphorylation. Activated by oxidative stress. The TXY motif contains the threonine and tyrosine residues whose phosphorylation activates the MAP kinases. Dually phosphorylated on Thr-186 and Tyr-188, which activates the enzyme. Belongs to the protein kinase superfamily. CMGC Ser/Thr protein kinase family. MAP kinase subfamily.