Characterization of Two Malaria Parasite Organelle Translation Elongation Factor G Proteins: The Likely Targets of the Anti-Malarial Fusidic Acid

Abstract

Malaria parasites harbour two organelles with bacteria-like metabolic processes that are the targets of many anti-bacterial drugs. One such drug is fusidic acid, which inhibits the translation component elongation factor G. The response of P. falciparum to fusidic acid was characterised using extended SYBR-Green based drug trials. This revealed that fusidic acid kills in vitro cultured P. falciparum parasites by immediately blocking parasite development. Two bacterial-type protein translation elongation factor G genes are identified as likely targets of fusidic acid. Sequence analysis suggests that these proteins function in the mitochondria and apicoplast and both should be sensitive to fusidic acid. Microscopic examination of protein-reporter fusions confirm the prediction that one elongation factor G is a component of parasite mitochondria whereas the second is a component of the relict plastid or apicoplast. The presence of two putative targets for a single inhibitory compound emphasizes the potential of elongation factor G as a drug target in malaria.

Arabidopsis thaliana mitochondrial EF-G1 functions in two different translation steps

“…To date, however, such an uncharacterized factor has not yet been discovered in these organisms. Our results and other recent findings (11,12,37) strongly indicate that AtEF-G1mt and P. falciparum EF-G1mt may play dual roles in their mitochondrial translation systems without requiring dual functional plastid EF-Gs. Metazoan EF-G1mt homologues are classified into one monophyletic group [group (e)] with Fungi, Heterolobosea and Amoebozoa.…”

“…Proteomic analysis by mass spectrometry suggests that A. thaliana chloroplast EF-G presents not only in chloroplasts but also in mitochondria (13), even though this EF-G is observed only in chloroplasts by fluorescence microscopy analysis (12). As another example, P. falciparum plastid EF-G and EF-G1mt [group (a)] are localized to apicoplast and mitochondrion, respectively (11). Additionally, it has been recently shown that both P. falciparum apicoplast EF-G and EF-G1mt possess ribosomal dissociation activity with apicoplast RRF (PfRRF1) and RRFmt (PfRRF2), respectively.…”

“…In the case of some Alveolata and Viridiplantae, there is no gene for EF-G2mt. Although fluorescence microscopy analyses suggest that two EF-G paralogues (EF-G1mt homologue and plastid EF-G) in Plasmodium falciparum are separately localized to the mitochondria and apicoplasts (apicomplexan plastid) (11) and one of two EF-G paralogues homologous to plastid EF-G in Arabidopsis thaliana (A. thaliana chloroplast EF-G) is localized to chloroplasts (12), more sensitive proteomic analyses by mass spectrometry have suggested that A. thaliana chloroplast EF-G presents not only in chloroplasts but also in mitochondria (13). Therefore, two possibilities are that: (i) uncharacterized factor(s), including chloroplast (plastid) EF-G, might cooperate with RRF for ribosome disassembly in their mitochondria or (ii) their mitochondrial EF-G1 homologues might possess dual functions contrary to the phylogenetic association with mammalian EF-G1mt, an exclusive translocase.…”

Inhibition of Protein Synthesis and Malaria Parasite Development by Drug Targeting of Methionyl-tRNA Synthetases

“…Almost 60% of encoded proteins appear to be unique to the parasite, reflecting great evolutionary distance between the parasite and the genomes of known eukaryotes (3). The malaria parasite (and the related apicomplexan Toxoplasma gondii) has three translationally active compartments, i.e., cytoplasm, apicoplasts, and mitochondria (4)(5)(6)(7)(8). All malaria parasite proteins involved in the protein synthesis machinery are encoded by the nuclear genome.…”

“…All malaria parasite proteins involved in the protein synthesis machinery are encoded by the nuclear genome. Either these proteins are transported to target organelles or their modified/activated substrates are transported across the organelles to perform required functions (4)(5)(6)(7)(8)(9). The primary enzymes responsible for translating genetic code into polypeptide chains are aminoacyl-tRNA synthetases (aaRSs).…”