Plasmodium falciparum calcium-dependent protein kinase phosphorylates proteins of the host erythrocytic membrane.
The unusual Ca(2+)-dependent protein kinase from Plasmodium falciparum (PfCPK) [1], whose gene structure and expression in bacteria have been reported [1], was purified to homogeneity. The purified recombinant kinase has a native molecular mass of 62,000, is activated by Ca2+ (K0.5 = 15 microM) in the presence of Mg2+ or Mn2+, and can associate with 45Ca2+. The activation by Ca2+ could be partially replaced by Mn2+, but not by Zn2+ or Mg2+. PfCPK preferentially phosphorylated casein and histone H1. The Km and Vmax for Mg2+ ATP were 26 microM and 70 nmol min-1 mg-1, respectively, with casein as substrate; and 34 microM and 143 nmol min-1 mg-1, respectively, with histone H1 as substrate. The kinase undergoes autophosphorylation on both serine and threonine residues. Calmodulin antagonists (calmidazolium, trifluoperazine, N-[6-aminohexyl]-5-chloro-1-napthalene-sulfonamide, and ophiobolin A) could inhibit the kinase activation, but much higher concentrations of the antagonists are needed than was required to inhibit calmodulin-mediated effects. PfCPK preferentially phosphorylates proteins of the host erythrocytic membrane in vitro but phosphorylates parasitic proteins only to a minor extent. The selectivity of the phosphorylation may be partially controlled by phosphatidylserine which is bound to some of the erythrocytic membrane proteins. Using a rabbit polyclonal antiserum against the recombinant protein, the kinase was found to be mainly expressed in the ring and schizont stages, and mainly localized in the parasitic membrane-organelle fraction and partially localized on the erythrocytic membrane.
Zhao
Y
Y
Department of Structural Biology, University of Basel, Switzerland.
Franklin
R M
RM
Kappes
B
B
D000818:Animals; D002147:Calmodulin / Q000037:antagonists & inhibitors; D004910:Erythrocyte Membrane / Q000378:metabolism*; D018507:Gene Expression Regulation, Developmental; D017125:Genes, Protozoan; D006651:Histocytochemistry; D066298:In Vitro Techniques; D008565:Membrane Proteins / Q000378:metabolism*; D008970:Molecular Weight; D010718:Phosphatidylserines / Q000494:pharmacology; D010766:Phosphorylation; D010963:Plasmodium falciparum / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development; D011494:Protein Kinases / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D015800:Protozoan Proteins / Q000378:metabolism; D013379:Substrate Specificity; D017871:Calcium-Calmodulin-Dependent Protein Kinases
D002147:Calmodulin; D008565:Membrane Proteins; D010718:Phosphatidylserines; D011494:Protein Kinases; D015800:Protozoan Proteins; D017871:Calcium-Calmodulin-Dependent Protein Kinases