Calcium-dependent protein kinase which acts as a sensor and effector of intracellular Ca(2+) levels probably in part downstream of cGMP-activated PKG kinase (PubMed:7808482). By phosphorylating various proteins, required for microneme secretion and thus merozoite egress from and invasion of host erythrocytes (By similarity). During gametogenesis, essential for the development of both male and female gametes (By similarity). Phosphorylates SERA5 p50 which enhances SERA5 p50 protease activity; however, SERA5 p50 protease activity has been shown in other studies to be controversial. Probably by phosphorylating SERA5 p50, plays a role in merozoite egress from host erythrocytes. Probably prior or during merozoite invasion of host erythrocytes, phosphorylates rhoptry protein RhopH3 which is required for RhopH3 localization to rhoptries and for its secretion. Probably in late schizonts, phosphorylates myosin A tail domain-interacting protein MTIP and glideosome-associated protein 45 GAP45, both of which are components of the motor complex that generates the force required by the parasite to invade host cells. In late schizonts, phosphorylates inner membrane complex protein IMC1g. In late schizonts, phosphorylates PKA regulatory subunit PKAr in a calcium-dependent manner, which may contribute to the dissociation of regulatory PKAr and catalytic PKAc subunits and promote the activation of PKAc. May phosphorylate raf kinase inhibitory protein RKIP which in turn may regulate CDPK1 catalytic activity (By similarity). May phosphorylate proteins of the host erythrocyte membranes (PubMed:7808482). ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] Can use both Mg(2+) and Mn(2+) in vitro and shows higher activity with Mn(2+) but Mg(2+) is likely to be the in vivo cofactor. Activated by calcium (PubMed:8440720, PubMed:8142371, PubMed:7808482). Upon calcium binding to the EF-hand domains, the C-terminus of the junction domain (J domain) undergoes a conformational change which results in the dissociation of the pseudo-substrate inhibitory motif from the catalytic domain (By similarity). This, in turn may facilitate the autophosphorylation of the activation loop at Thr-231, which leads to the kinase activation (By similarity). Inhibited by calmodulin antagonists such as calmidazolium, trifluoperazine, N-[6-aminohexyl]-5-chloro-1-naphthalene-sulfonamide, and ophiobolin A (PubMed:7808482). Monomer. Forms a high molecular weight (250 and 400 kDa) complex. Forms a complex composed of CDPK1, PKA regulatory subunit PKAr and 14-3-3I; the complex is formed in merozoites in response to low extracellular level of K(+) and may play a role in microneme secretion. Interacts (when phosphorylated) with 14-3-3I in a Ca(2+)-independent manner; the interaction does not regulate CDPK1 catalytic activity but is required for merozoite invasion of host erythrocytes. Interacts with PKA regulatory subunit PKAr; in a Ca(2+)-dependent manner. Interacts with SERA5 p50 in the late schizont stage. Interacts with inner membrane complex protein IMC1g in late schizonts. Interacts with rhoptry protein RhopH3 in merozoites. Localizes to the host erythrocytic membrane at low level (PubMed:7808482). Localizes to the cell membrane in the nascent merozoites contained within the late-stage schizonts and in free merozoites. Colocalizes with MTIP around developing merozoites in segmented schizonts, also localizes in membranes around the mature food vacuole/residual body of the schizonts. Ser-64 phosphorylated form localizes at the apical pole in punctate structures in merozoites within late schizonts in free merozoites. In trophozoites and schizonts, localizes to the parasitophorous vacuole (PV) and in membranous systems derived from the PV including intraparasitic vacuoles and the tubovesicular system, an extension of the parasitophorous vacuole membrane into the host cell cytoplasm. Localization to the cytoplasm in trophozoite or schizonts is minimal (By similarity). In female stage V gametocytes and gametes, localizes to the cell membrane. In stage V male gametocytes, localizes to the cell membrane and in the cytoplasm. In male gametes, localizes to the residual body, cell membrane and in the flagella (By similarity). Calcium and/or autophosphorylation does not affect membrane localization (By similarity). Expressed in ring and schizont stages and to a lesser extent in early and late trophozoite stages. The junction domain (J domain) is composed of 2 motifs that maintain the kinase inactive. The N-terminal autoinhibitory motif acts as a pseudosubstrate inhibiting the catalytic domain while the C-terminal motif binds the EF-hand domains. Myristoylated. Myristoylation, palmitoylation and the basic cluster motif are required for the localization to the parasitophorous vacuole membrane. Palmitoylated. Palmitoylation increases in merozoites in response to low level of extracellular K(+) in the host blood. Myristoylation, palmitoylation and the basic cluster motif are required for the localization to the parasitophorous vacuole membrane. Phosphorylation at Ser-64 occurs at late schizont stage and regulates CDPK1 protein-protein interaction. Phosphorylated at Ser-28, Ser-34 and Ser-64 in merozoites in response to low extracellular level of K(+). Phosphorylation at Thr-231 may regulate CDPK1 kinase activity. Phosphorylation increases in response to an increase in intracellular Ca(2+) levels (By similarity). Autophosphorylated in vitro (PubMed:7808482). Autophosphorylation does not affect membrane localization in vitro (By similarity). Belongs to the protein kinase superfamily. Ser/Thr protein kinase family. CDPK subfamily.