title: Cyclin H activation and drug susceptibility of the Pfmrk cyclin dependent protein kinase from Plasmodium falciparum.
abstract: The eukaryotic cell cycle is regulated by a group of highly conserved cyclin dependent protein kinases (CDKs). Several CDKs have been identified in Plasmodium falciparum, however, their regulatory mechanisms as well as their role in parasite growth and differentiation are not understood fully. To further our understanding of Plasmodium CDK regulation, we have characterized Pfmrk kinase activity. Pfmrk was expressed and purified as a 6xHis tagged recombinant protein from Escherichia coli and assayed for histone H1 kinase activity. Pfmrk has significant histone H1 kinase activity and is autophosphorylated in vitro. Human cyclin H forms a stable complex with Pfmrk and stimulates kinase activity. This is the first indication that Plasmodial CDKs are partially regulated by cyclin subunits, as are human CDKs. CDKs are attractive drug targets due to their role in cellular proliferation. Specific CDK inhibitors were selected to evaluate Pfmrk as a potential drug target. Olomoucine and roscovitine failed to inhibit Pfmrk kinase activity which places Pfmrk with a class of CDKs that are insensitive to these compounds. A molecular model of Pfmrk provides a structural explanation for the failure of these compounds to inhibit Pfmrk.
authors.affiliation: Division of Experimental Therapeutics, Walter Reed Army Institute of Research, Washington, DC 20307-5100, USA. norman.waters@na.amedd.army.mil
authors.forename: N C
authors.initials: NC
authors.lastname: Waters
authors.forename: C L
authors.initials: CL
authors.lastname: Woodard
authors.forename: S T
authors.initials: ST
authors.lastname: Prigge
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D056748:Cyclin H; D018844:Cyclin-Dependent Kinases / Q000037:antagonists & inhibitors; D016213:Cyclins / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D007701:Kinetin; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010963:Plasmodium falciparum / Q000201:enzymology*; D011487:Protein Conformation; D011494:Protein Kinases / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D011687:Purines / Q000494:pharmacology; D000077546:Roscovitine; D000095043:Cyclin-Dependent Kinase-Activating Kinase
chemical_list: C534751:CCNH protein, human; D056748:Cyclin H; D016213:Cyclins; D004791:Enzyme Inhibitors; D011687:Purines; D000077546:Roscovitine; C090046:olomoucine; D011494:Protein Kinases; C102333:histone H1 kinase; D017346:Protein Serine-Threonine Kinases; D018844:Cyclin-Dependent Kinases; D007701:Kinetin; D000095043:Cyclin-Dependent Kinase-Activating Kinase