ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] In the N-terminal section; belongs to the GDT family. In the C-terminal section; belongs to the protein kinase superfamily. TKL Ser/Thr protein kinase family.