ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] Is highly expressed during the young trophozoite stage but gradually decreases in amount with further growth. No protein can be detected during the ring stage, only small amount is expressed during the schizont stage. Belongs to the protein kinase superfamily. Ser/Thr protein kinase family.