Serine/threonine-protein kinase involved in a signal transduction pathway that is activated by changes in the osmolarity of the extracellular environment. ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] Activated by Ser-520 phosphorylation by HOG1. Autophosphorylated. Phosphorylated by HOG1 at Ser-520 after osmotic stress. Present with 1790 molecules/cell in log phase SD medium. Belongs to the protein kinase superfamily. CAMK Ser/Thr protein kinase family. CaMK subfamily.