ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] Ovotestis. Concentrated in meiotic and postmeiotic spermatogenic cells. Belongs to the protein kinase superfamily. AGC Ser/Thr protein kinase family. cAMP subfamily.