Developing chemical biological tools to probe phosphorylation in P. falciparum

In 2010 there were an estimated 219 million cases of malaria worldwide, accounting for approximately 0.66 million deaths. With growing resistance to current antimalarial agents a challenge is placed on the scientific community to provide efficacious and cost effective methods for the diagnosis and treatment of malaria. As protein phosphorylation regulates most aspects of cell life, understanding the function of protein kinases in malaria parasites has the potential to uncover novel drug targets. To this end, this work focused on the study of three essential Plasmodium falciparum kinases using two different chemical genetic approaches: γ-modified ATP analogues for the investigation of PfCK2; and covalent complementarity for the study of PfCLK1 and PfCLK3. The work presented here highlights the instability of the P-N bond of ATP phosphoramidates during the acidic conditions required for analysis by MALDI-TOF MS and seeks to overcome this through the development of alternative linkers to the γ-phosphate of ATP. Apparent IC[subscript 50] values recorded provide evidence of PfCK2α tolerating modification of the γ-phosphoryl group of ATP; however, no evidence was found to support GTP serving as an alternative co-substrate of PfCK2α. The gatekeeper mutant kinases PfCLK1F630C and PfCLK3F444C were successfully produced. It was found that this mutation rendered PfCLK3 inactive and was detrimental to the activity of PfCLK1. Under the conditions used PfCLK1F630C was not inhibited by a panel of 23 electrophilic inhibitors.