Serine/threonine protein kinase involved in a signal transduction pathway that plays a role in yeast cell morphogenesis and cell growth. This pathway seems to start by SMP3; then involve the kinase PKC1 that may act the BCK1 kinase that then phosphorylates MKK1 and MKK2 which themselves phosphorylate the SLT2/MPK1 kinase which itself then phosphorylates and activates the transcription factor RLM1. Directly phosphorylates BCY1 upon TOR complex 1 (TORC1) inhibition. ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] Activated by tyrosine and threonine phosphorylation by MKK1 and MKK2. Interacts with RLM1. The TXY motif contains the threonine and tyrosine residues whose phosphorylation activates the MAP kinases. Dually phosphorylated on Thr-190 and Tyr-192, which activates the enzyme. Present with 3230 molecules/cell in log phase SD medium. Belongs to the protein kinase superfamily. CMGC Ser/Thr protein kinase family. MAP kinase subfamily.