ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] Up-regulated by Ca(2+)/CaM. Interacts with calmodulin (CaM) in a Ca(2+)-dependent manner. By cold, salt, abscisic acid (ABA) and hydrogen peroxide. Autophosphorylated. Belongs to the protein kinase superfamily. Ser/Thr protein kinase family.