title: Characterization of Plasmodium falciparum calcium-dependent protein kinase 4.
abstract: In Plasmodium berghei, the orthologous gene of P. falciparum calcium-dependent protein kinase 4 (PfCDPK4) was reported to be essential for the exflagellation of male gametocytes. To elucidate the role of PfCDPK4 in P. falciparum gametogenesis, we characterized the biological function of PfCDPK4 in vitro. PfCDPK4 was purified as a fusion protein that was labeled with [gamma-(32)P]ATP; this labeling was then eliminated by phosphatase. Phosphorylation activity of PfCDPK4 was eliminated when its putative catalytic lysine residue was replaced with alanine. In biochemical analyses, PfCDPK4 was found to have characteristics that were similar to those of homologous proteins from plants. PfCDPK4 phosphorylation was activated when experimental conditions were changed from those characteristic of human blood (37 degrees C, pH 7.4) to those of the mosquito bloodmeal (at least 5 degrees C below 37 degrees C, pH 7.6, with xanthurenic acid (XA)). PfCDPK4 was overexpressed in day 15 gametocytes exposed to XA or human serum. Thus, PfCDPK4 phosphorylation is activated by an increase in Ca(2+) concentration or pH and by a decrease in temperature, and is associated with the Ca(2+) signals that facilitate P. falciparum gametogenesis.
authors: Department of Veterinary Microbiology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo, Japan. akkato@mail.ecc.u-tokyo.ac.jp
authors: Kentaro
authors: K
authors: Kato
authors: Atsushi
authors: A
authors: Sudo
authors: Kyousuke
authors: K
authors: Kobayashi
authors: Tatsuki
authors: T
authors: Sugi
authors: Yukinobu
authors: Y
authors: Tohya
authors: Hiroomi
authors: H
authors: Akashi
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling; D029966:Centaurium / Q000469:parasitology; D009033:Culicidae / Q000469:parasitology; D006790:Host-Parasite Interactions; D006801:Humans; D006863:Hydrogen-Ion Concentration; D010766:Phosphorylation; D010963:Plasmodium falciparum / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics / Q000502:physiology*; D011494:Protein Kinases / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D013696:Temperature; D014977:Xanthurenates / Q000494:pharmacology; D017871:Calcium-Calmodulin-Dependent Protein Kinases
chemical_list: D002118:Calcium; D011494:Protein Kinases; D011993:Recombinant Fusion Proteins; D014977:Xanthurenates; D017871:Calcium-Calmodulin-Dependent Protein Kinases; C028330:xanthurenic acid