Activation of a Plasmodium falciparum cdc2-related kinase by heterologous p25 and cyclin H. Functional characterization of a P. falciparum cyclin homologue.
Several Plasmodium falciparum genes encoding cdc2-related protein kinases have been identified, but the modalities of their regulation remains largely unexplored. In the present study, we investigated the regulation in vitro of PfPK5, a putative homologue of Cdk1 (cdc2) in P. falciparum. We show that (i) PfPK5 is efficiently activated by heterologous (human) cyclin H and p25, a cyclin-like molecule that specifically activates human Cdk5; (ii) the activated enzyme can be inhibited by chemical Cdk inhibitors; (iii) Pfmrk, a putative P. falciparum homologue of the Cdk-activating kinase, does neither activate nor phosphorylate PfPK5; and (iv) PfPK5 is able to autophosphorylate in the presence of a cyclin. Taken together, these results suggest that the regulation of Plasmodium Cdks may differ in important aspects from that of their human counterparts. Furthermore, we cloned an open reading frame encoding a novel P. falciparum protein possessing maximal homology to cyclin H from various organisms, and we show that this protein, called Pfcyc-1, is able to activate recombinant PfPK5 in vitro with an efficiency similar to that of human cyclin H and p25. This work opens the way to the development of screening procedures aimed at identifying compounds that specifically target the parasite Cdks.
Le Roch
K
K
INSERM, Unité 511, 91 Bd. de l'Hôpital, 75013 Paris, France.
Sestier
C
C
Dorin
D
D
Waters
N
N
Kappes
B
B
Chakrabarti
D
D
Meijer
L
L
Doerig
C
C
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D016203:CDC2 Protein Kinase; D056748:Cyclin H; D016213:Cyclins / Q000235:genetics / Q000378:metabolism*; D004789:Enzyme Activation; D006657:Histones / Q000378:metabolism; D008969:Molecular Sequence Data; D010766:Phosphorylation; D010963:Plasmodium falciparum / Q000201:enzymology* / Q000235:genetics; D011485:Protein Binding; D015800:Protozoan Proteins; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity
C534751:CCNH protein, human; D056748:Cyclin H; D016213:Cyclins; D006657:Histones; C406811:PfPK5 protein, Plasmodium falciparum; D015800:Protozoan Proteins; D016203:CDC2 Protein Kinase