Plasmodium falciparum is responsible for most dangerous and prevalent form of malaria. The emergence of multi drug resistant parasite hindered the prevention of malaria burden worldwide. Helicases are omnipresent enzymes, which play important role in nucleic acid metabolism and can be used as potential targets for development of novel therapeutics. The genome wide analysis of P. falciparum 3D7 strain revealed some novel parasite specific helicases, which are not present in human host. Here we report the detailed biochemical characterization of P. falciparum parasite specific helicase 3 (PfPSH3). The characteristic ATPase and helicase activities of PfPSH3 reside in its N-terminal region (PfPSH3N) as it contains all the conserved signature motifs whereas the C-terminal does not show any detectable biochemical activity. PfPSH3N also shows DNA helicase activity in the 3′–5′ direction. The immunofluorescence microscopy results show that PSH3 is localized in nucleus as well as in cytoplasm during different stages such as trophozoite and early schizont stages of intraerythrocytic development. This report sets the foundation for further study of parasite specific helicases and will be helpful in understanding the parasite biology.
Malaria a major parasitic infection globally particularly in tropical and sub-tropical regions of the world is responsible for about 198 million cases and estimated deaths due to this disease are about 0.6 million. The emergence of drug resistance in the malaria parasite is alarming and it is necessary to understand its underlying cause and molecular mechanisms. It has been established that drug resistant malaria parasites have defective mismatch repair (MMR) therefore it is essential to study this pathway and its components in detail. Recently a number of non-synonymous Single Nucleotide Polymorphisms have been reported in genes involved in MMR pathways. PfMLH is an endonuclease essential to restore the MMR in drug resistant strains of Plasmodium falciparum. Considering all these facts about the role of MMR in emergence of drug resistant parasite, in this manuscript we report a genome wide analysis of the components of the MMR pathway such as MLH, Pms1, MSH2-1, MSH2-2, MSH6, and UvrD using in silico bioinformatics based approaches. The phylogenetic analysis revealed evolutionary closeness with the MMR components of various organisms. It is noteworthy that P. falciparum contains two homologs of MSH2, which are located on different chromosomes. The structural modeling of these components showed their similarity with the human/yeast MMR components. The docking studies reveal that PfUvrD and PfMLH interact with each other. The in silico identification of interacting partners of the major MMR components identified numerous P. falciparum specific proteins. In line with our previous studies the present study will also contribute significantly to understand the MMR pathway of malaria parasite.
Human malaria infection is a major challenge across the globe and is responsible for millions of deaths annually. Rapidly emerging drug resistant strains against the new class of anti-malarial drugs are major threat to control the disease burden worldwide. Helicases are present in every organism and have important role in various nucleic acid metabolic processes. Previously we have reported the presence of three parasite specific helicases (PSH) in Plasmodium falciparum 3D7 strain. Here we present the detailed biochemical characterization of PfPSH2. PfPSH2 is DNA and RNA stimulated ATPase and is able to unwind partially duplex DNA and RNA substrates. It can translocate in both 3′ to 5′ and 5′ to 3′ directions. PfPSH2 is expressed in all the stages of intraerythrocytic development and it is localized in cytoplasm in P. falciparum 3D7 strain. The dsRNA mediated inhibition study suggests that PfPSH2 is important for the growth and survival of the parasite. This study presents the detailed characterization of PfPSH2 and lays the foundation for future development of PfPSH2 as drug target.
Malaria is one of the major global health concerns still prevailing in this 21st century. Even the effect of artemisinin combination therapies (ACT) have declined and causing more mortality across the globe. Therefore, it is important to understand the basic biology of malaria parasite in order to find novel drug targets. Helicases play important role in nucleic acid metabolism and are components of cellular machinery in various organisms. In this manuscript we have performed the biochemical characterization of homologue of DDX17 from Plasmodium falciparum (PfDDX17). Our results show that PfDDX17 is an active RNA helicase and uses mostly ATP for its function. The qRT-PCR experiment results suggest that PfDDX17 is highly expressed in the trophozoite stage and it is localised mainly in the cytoplasm and in infected RBC (iRBC) membrane mostly in the trophozoite stage. The dsRNA knockdown study suggests that PfDDX17 is important for cell cycle progression. These studies report the biochemical functions of PfDDX17 helicase and further augment the fundamental knowledge about helicase families of P. falciparum .
Malaria, a disease caused by infection with parasites of the genus Plasmodium, causes millions of deaths worldwide annually. Of the five Plasmodium species that can infect humans, Plasmodium falciparum causes the most serious parasitic infection. The emergence of drug resistance and the ineffectiveness of old therapeutic regimes against malaria mean there is an urgent need to better understand the basic biology of the malaria parasite. Previously, we have reported the presence of parasite‐specific helicases identified through genome‐wide analysis of the P. falciparum (3D7) strain. Helicases are involved in various biological pathways in addition to nucleic acid metabolism, making them an important target of study. Here, we report the detailed biochemical characterization of P. falciparum parasite‐specific helicase 1 (PfPSH1) and the effect of phosphorylation on its biochemical activities. The C‐terminal of PfPSH1 (PfPSH1C) containing all conserved domains was used for biochemical characterization. PfPSH1C exhibits DNA‐ or ribonucleic acid (RNA)‐stimulated ATPase activity, and it can unwind DNA and RNA duplex substrates. It shows bipolar directionality because it can translocate in both (3′–5′ and 5′–3′) directions. PfPSH1 is mainly localized to the cytoplasm during early stages (including ring and trophozoite stages of intraerythrocytic development), but at late stages, it is partially located in the cytoplasm. The biochemical activities of PfPSH1 are upregulated after phosphorylation with PKC. The detailed biochemical characterization of PfPSH1 will help us understand its functional role in the parasite and pave the way for future studies.
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