Malaria remains a global health problem, despite over a century of efforts towards control and prevention. It is responsible for over 2 million deaths a year. Plasmodium falciparum, the protozoan parasite that causes malaria, presents quite an unexplored field of study, significant both for the purposes of understanding the complex life cycle of the parasite, and for identifying novel and unique targets for anti-malarial therapy. Cyclin-dependent kinases. (CDK.s) play a number of crucial roles in the progression of the cell cycle such as regulating the onset of DNA replication and entry into mitosis. Plasmodium falciparum protein kinase 5, PfPK5, manifests characteristics of eukaryotic CDKs. It is a serine/threonine kinase, has 60% amino acid identity to eukaryotic cyclin-dependent kinase cdc2, and shares the mechanism of activation with CDKs. To establish if PfPK5 indeed is the major cell cycle regulatory kinase, as well as to expand our knowledge about the signaling networks of the parasite, it is necessary to identify proteins that interact with the kinase, such as its putative substrates. Currently, only one Plasmodium falciparum protein is known to interact with PfPK5 - its cyclin partner, Pfcycl. Identifying substrates of PfPKS is a particularly important research endeavor since it would provide insight into the yet unknown downstream signaling pathways of PfPK5. It is likely that pathways unique to Plasmodium falciparum will be found, which may be specifically targeted for anti-malaria therapy. A potential substrate of Plasmodium falciparum cell cycle regulatory kinase PfPK5 has been identified. The new protein, which we call SPOK, was identified by screening a phage display cDNA library. Since SPOK is a large protein of approximately 140kDa, a domain containing a tandem CDK/cdc2 phosphorylation motif of SPEK (single amino acid code, S/TPXK/R) was expressed in E.coli. Our results show that this domain of SPOK is indeed phosphorylated in vitro by PfPK5. This raises the possibility that SPOK could be an in vivo substrate of PfPK5 and may play a role in regulating the cell cycle of the parasite.
| Identifer | oai:union.ndltd.org:ucf.edu/oai:stars.library.ucf.edu:honorstheses1990-2015-1329 |
| Date | 01 January 2003 |
| Creators | Kachirskaia, Ioulia |
| Publisher | STARS |
| Source Sets | University of Central Florida |
| Language | English |
| Detected Language | English |
| Type | text |
| Source | HIM 1990-2015 |
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