Molecular cloning of Plasmodium vivax calcium-dependent protein kinase 4

A family of calcium-dependent protein kinases (CDPKs) is a unique enzyme which plays crucial roles in intra- cellular calcium signaling in plants, algae, and protozoa. CDPKs of malaria parasites are known to be key regulators for stage-specific cellular responses to calcium, a widespread secondary messenger that controls the progression of the pa- rasite. In our study, we identified a gene encoding Plasmodium vivax CDPK4 (PvCDPK4) and characterized its molecular property and cellular localization. PvCDPK4 was a typical CDPK which had well-conserved N-terminal kinase domain and C-terminal calmodulin-like structure with 4-EF hand motifs for calcium-binding. The recombinant protein of EF hand domain of PvCDPK4 was expressed in Echerichia coli and a 34 kDa product was obtained. Immunofluorescence assay by confocal laser microscopy revealed that the protein was expressed at the mature schizont of P. vivax. The expression of Pv- CDPK4-EF in schizont suggests that it may participate in the proliferation or egress process in the life cycle of this parasite.