SAM domain-dependent activity of PfTKL3, an essential tyrosine kinase-like kinase of the human malaria parasite Plasmodiumfalciparum

Over the last decade, several protein kinases inhibitors have reached the market for cancer chemotherapy. The kinomes of pathogens represent potentially attractive targets in infectious diseases. The functions of the majority of protein kinases of Plasmodium falciparum, the parasitic protist responsible for the most virulent form of human malaria, remain unknown. Here we present a thorough characterisation of PfTKL3 (PF13_0258), an enzyme that belongs to the tyrosine kinase-like kinase (TKL) group. We demonstrate by reverse genetics that PfTKL3 is essential for asexual parasite proliferation in human erythrocytes. PfTKL3 is expressed in both asexual and gametocytes stages, and in the latter the protein co-localises with cytoskeleton microtubules. Recombinant PfTKL3 displays in vitro autophosphorylation activity and is able to phosphorylate exogenous substrates, and both activities are dramatically dependent on the presence of an N-terminal “sterile α-motif” domain. This study identifies PfTKL3 as a validated drug target amenable to high-throughput screening

Protein kinases of the human malaria parasite Plasmodium falciparum: the kinome of a divergent eukaryote

<p>Abstract</p> <p>Background</p> <p>Malaria, caused by the parasitic protist <it>Plasmodium falciparum</it>, represents a major public health problem in the developing world. The <it>P. falciparum </it>genome has been sequenced, which provides new opportunities for the identification of novel drug targets. Eukaryotic protein kinases (ePKs) form a large family of enzymes with crucial roles in most cellular processes; hence malarial ePKS represent potential drug targets. We report an exhaustive analysis of the <it>P. falciparum </it>genomic database (PlasmoDB) aimed at identifying and classifying all ePKs in this organism.</p> <p>Results</p> <p>Using a variety of bioinformatics tools, we identified 65 malarial ePK sequences and constructed a phylogenetic tree to position these sequences relative to the seven established ePK groups. Predominant features of the tree were: (i) that several malarial sequences did not cluster within any of the known ePK groups; (ii) that the CMGC group, whose members are usually involved in the control of cell proliferation, had the highest number of malarial ePKs; and (iii) that no malarial ePK clustered with the tyrosine kinase (TyrK) or STE groups, pointing to the absence of three-component MAPK modules in the parasite. A novel family of 20 ePK-related sequences was identified and called FIKK, on the basis of a conserved amino acid motif. The FIKK family seems restricted to Apicomplexa, with 20 members in <it>P. falciparum </it>and just one member in some other <it>Apicomplexan </it>species.</p> <p>Conclusion</p> <p>The considerable phylogenetic distance between Apicomplexa and other Eukaryotes is reflected by profound divergences between the kinome of malaria parasites and that of yeast or mammalian cells.</p

Regulation of Plasmodium falciparum Pfnek3 relies on phosphorylation at its activation loop and at threonine 82

10.1007/s00018-009-0101-8Cellular and Molecular Life Sciences66183081-309