Serine/threonine protein kinase which acts as a downstream effector of the second messenger cGMP (PubMed:11897122, PubMed:12455981). Plays an essential role in tachyzoite invasion of and egress from host cells (PubMed:28465425, PubMed:30753127, PubMed:31235476). During invasion of host cells, regulates the apico-basal flux of F-actin probably via Ca(2+)-mediated activation of CDPK1 (PubMed:30753127). In tachyzoites, required for microneme secretion (PubMed:26933037, PubMed:28465425). Required for tachyzoite gliding motility (PubMed:31235476). Plays an essential role in parasite invasion of and egress from host cells, and microneme secretion. Dispensable for parasite invasion of and egress from host cells, and microneme secretion. ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] Activated by cGMP (PubMed:11897122, PubMed:12455981). The cGMP-binding domains acts cooperatively to activate PKG (PubMed:11897122, PubMed:12455981). Inhibited by the antiparasitic small molecule 4-[2-(4-fluorophenyl)-5-(1-methylpiperidine-4-yl)-1Hpyrrol- 3-yl]pyridine (compound 1) (PubMed:11897122, PubMed:12455981). Membrane localization is essential to regulate parasite invasion, egress and microneme secretion. Expressed in tachyzoites (at protein level). Knockout in tachyzoites is lethal (PubMed:12455981). Conditional knockout in tachyzoites impairs lytic growth in host cells (PubMed:28465425, PubMed:31235476). However, parasite intracellular replication is only slightly affected (PubMed:31235476). Impaired microneme secretion, motility and, invasion of and egress from host cells (PubMed:28465425, PubMed:31235476). Impaired growth in host cells (PubMed:28465425). Impaired microneme secretion and, invasion of and egress from host cells (PubMed:28465425). Normal growth in host cells (PubMed:28465425). Microneme secretion and, invasion of and egress from host cells are partially impaired (PubMed:28465425). Belongs to the protein kinase superfamily. AGC Ser/Thr protein kinase family. cGMP subfamily.