Serine-threonine protein kinase which may be involved in pheromone signaling. Functionally complements the MAPK pheromone signaling pathway 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] Divalent cations including magnesium and manganese. Activated by tyrosine and threonine phosphorylation (By similarity). Inhibited by the MEK inhibitor U0126 but not by the p38 inhibitor SB203580. Cobalt abolishes kinase activity, while calcium, copper and nickel have little effect on kinase activity. Optimum pH is 6.5. Optimum temperature is 30-35 degrees Celsius. Activity is significantly higher in trophic forms than in cysts. The TXY motif contains the threonine and tyrosine residues whose phosphorylation activates the MAP kinases. Dually phosphorylated on Thr-176 and Tyr-178, which activates the enzyme. Belongs to the protein kinase superfamily. CMGC Ser/Thr protein kinase family. MAP kinase subfamily.