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Updated: May 6, 2026
Methods to Investigate the Regulatory Role of Small RNAs and Ribosomal Occupancy of Plasmodium falciparum
Published on: December 4, 2015
The effect of fusidic acid on Plasmodium falciparum elongation factor G (EF-G)
Ankit Gupta1, Snober S Mir1, Uzma Saqib1
1Division of Molecular and Structural Biology, CSIR-Central Drug Research Institute, Lucknow, India.
Abstract:
Inhibition of growth of the malaria parasite Plasmodium falciparum by known translation-inhibitory antibiotics has generated interest in understanding their action on the translation apparatus of the two genome containing organelles of the malaria parasite: the mitochondrion and the relic plastid (apicoplast). We report GTPase activity of recombinant EF-G proteins that are targeted to the organelles and further use these to test the effect of the EF-G inhibitor fusidic acid (FA) on the factor-ribosome interface. Our results monitoring locking of EF-G·GDP onto surrogate Escherichia coli ribosomes as well as multi-turnover GTP hydrolysis by the factor indicate that FA has a greater effect on apicoplast EF-G compared to the mitochondrial counterpart. Deletion of a three amino acid (GVG) sequence in the switch I loop that is conserved in proteins of the mitochondrial EF-G1 family and the Plasmodium mitochondrial factor, but is absent in apicoplast EF-G, demonstrated that this motif contributes to differential inhibition of the two EF-Gs by FA. Additionally, the drug thiostrepton, that is known to target the apicoplast and proteasome, enhanced retention of only mitochondrial EF-G on ribosomes providing support for the reported effect of the drug on parasite mitochondrial translation.
Insights
Antibiotics targeting malaria parasite growth were studied. Fusidic acid more strongly inhibits apicoplast EF-G than mitochondrial EF-G, revealing differences in organelle translation machinery.
Area of Science:
- Molecular Parasitology
- Antimicrobial Drug Action
- Organelle Biology
Background:
- The malaria parasite Plasmodium falciparum possesses two organelles, the mitochondrion and apicoplast, each with its own translation system.
- Translation-inhibitory antibiotics are known to affect parasite growth, prompting investigation into their specific targets within these organelles.
Purpose of the Study:
- To investigate the differential effects of antibiotics on the elongation factor G (EF-G) proteins in the malaria parasite's mitochondrion and apicoplast.
- To elucidate the molecular basis for the differential inhibition of organellar EF-G proteins by fusidic acid.
Main Methods:
- Recombinant EF-G proteins from Plasmodium falciparum's mitochondrion and apicoplast were expressed and their GTPase activity was measured.
- The effect of fusidic acid (FA) on EF-G-ribosome interactions was assessed using surrogate Escherichia coli ribosomes.
- Mutational analysis involving deletion of a conserved GVG motif in the switch I loop of EF-G was performed.
Main Results:
- Fusidic acid exhibited a greater inhibitory effect on apicoplast EF-G compared to mitochondrial EF-G.
- Deletion of the GVG motif in the switch I loop of EF-G abolished the differential inhibition by fusidic acid.
- Thiostrepton enhanced the retention of mitochondrial EF-G on ribosomes, supporting its known effect on parasite mitochondrial translation.
Conclusions:
- The GVG motif in the switch I loop of EF-G contributes to the differential sensitivity of mitochondrial and apicoplast EF-G to fusidic acid.
- These findings highlight distinct features of the translation apparatus in Plasmodium falciparum's organelles and offer insights into targeted drug development.
