ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] Mg(2+). Mn(2+) is seen in the crystal structure; there are 2 Mn(2+) ions in the ATP-bound crystal and 1 Mn(2+) in the ADP-bound crystal. Monomer. Autophosphorylated. Belongs to the protein kinase superfamily. RIO-type Ser/Thr kinase family.