Serine/threonine-protein kinase (By similarity). Involved in the control of the cell cycle. Required for entry into S-phase and mitosis (By similarity). Probable component of the kinase complex that phosphorylates the repetitive C-terminus of RNA polymerase II (By similarity). ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] [DNA-directed RNA polymerase] + ATP = ADP + H(+) + phospho-[DNA-directed RNA polymerase] Phosphorylation at Thr-14 or Tyr-15 inactivates the enzyme, while phosphorylation at Thr-158 activates it. May form a complex composed of at least the catalytic subunit CRK2 and a cyclin. Expressed at a low level during the asexual cell-cycle within the host erythrocytes. Also expressed in gametocytes and in stages during development in the mosquito. Normal asexual development in host erythrocytes, normal ookinete and oocyte development in the mosquito vector, normal number of oocyte and salivary gland sporozoites (PubMed:20951971). Normal transmission into the mouse host (PubMed:20951971). Belongs to the protein kinase superfamily. CMGC Ser/Thr protein kinase family. CDC2/CDKX subfamily.