Related Experiment Video

Updated: Aug 23, 2026

Genetic Manipulation in Δku80 Strains for Functional Genomic Analysis of Toxoplasma gondii
09:52

Genetic Manipulation in Δku80 Strains for Functional Genomic Analysis of Toxoplasma gondii

Published on: July 12, 2013

Mitochondrial tRNA import in Toxoplasma gondii

Anne Crausaz Esseiva1, Arunasalam Naguleswaran, Andrew Hemphill

  • 1Department of Biology/Zoology, University of Fribourg, Chemin du Musée 10, CH-1700 Fribourg, Switzerland.

The Journal of Biological Chemistry
|July 29, 2004
PubMed

Insights

Apicomplexan parasites, like Toxoplasma gondii, import all necessary transfer RNAs (tRNAs) for mitochondrial protein synthesis from the cell's cytosol. This study provides the first experimental proof of this essential tRNA import mechanism in these parasites.

Area of Science:

  • Molecular Biology
  • Parasitology
  • Cell Biology

Background:

  • Apicomplexan parasites possess the smallest known mitochondrial genomes, lacking tRNA genes.
  • This necessitates the import of all tRNAs for mitochondrial translation from the cytosol.
  • Previous studies postulated this import mechanism but lacked direct experimental evidence.

Purpose of the Study:

  • To provide direct experimental evidence for the import of tRNAs into apicomplexan mitochondria.
  • To investigate the specificity of tRNA import in apicomplexans, comparing it to related taxa.
  • To analyze the role of specific tRNAs and modifications in the import process.

Main Methods:

  • Development of a cell fractionation procedure to isolate organellar RNA from *Toxoplasma gondii*.
  • Northern hybridization analysis of total and organellar RNA fractions.
  • Expression of *Toxoplasma gondii* initiator tRNAMet in *Trypanosoma brucei*.

Main Results:

  • Nucleus-encoded tRNAs, except for the initiator tRNAMet, were detected in both the cytosol and mitochondria of *Toxoplasma gondii*.
  • This confirms the import of nuclear-encoded tRNAs into apicomplexan mitochondria.
  • The import specificity mirrors that of trypanosomatids, with the initiator tRNAMet being cytosol-specific.
  • Thio-modifications were absent in *T. gondii* tRNAGln, suggesting they are not involved in import regulation.

Conclusions:

  • This study provides the first experimental evidence for mitochondrial tRNA import in apicomplexans.
  • The import mechanism and specificity are conserved between apicomplexans and trypanosomatids.
  • The initiator tRNAMet plays a crucial role in directing its localization to the cytosol in both parasite groups.

More Related Videos

Determination of Chemical Inhibitor Efficiency against Intracellular Toxoplasma Gondii Growth Using a Luciferase-Based Growth Assay09:49

Determination of Chemical Inhibitor Efficiency against Intracellular Toxoplasma Gondii Growth Using a Luciferase-Based Growth Assay

Published on: April 29, 2020

Measurement of Protein Import Capacity of Skeletal Muscle Mitochondria09:01

Measurement of Protein Import Capacity of Skeletal Muscle Mitochondria

Published on: January 7, 2022

Related Concept Videos

Mitochondrial Precursor Proteins01:39

Mitochondrial Precursor Proteins

Mitochondrial precursors are partially unfolded or loosely folded polypeptide chains. Newly synthesized precursors are inhibited from spontaneously folding into their native conformation by the cytosolic chaperones, heat shock proteins 70 (Hsp70), and mitochondrial import stimulation factors (MSFs). Precursors bound to MSFs are guided to the TOM70-TOM37 receptors, while precursors bound to Hsp70  chaperones are targetted to TOM20-TOM22 receptor complexes.
Most of the mitochondrial precursors...
Mitochondrial Protein Sorting01:39

Mitochondrial Protein Sorting

Mitochondria are double-membrane organelles of the eukaryotes involved in cellular metabolism, signaling, ATP synthesis, and programmed cell death.  Each of these processes requires specific proteins and enzymes that must be correctly sorted to the right mitochondrial subcompartment for the proper functioning of the organelle.
Most of these mitochondrial proteins are encoded by the nucleus and imported to the mitochondria as unfolded or loosely folded precursors. Mitochondrial precursors...
Protein Transport into the Inner Mitochondrial Membrane01:34

Protein Transport into the Inner Mitochondrial Membrane

Nuclear encoded mitochondrial precursors are imported to the inner membrane in a multistep process involving two separate translocons, TIM22 and TIM23. TIM23 is a cation-selective pore that remains closed by the N terminal segment of the protein. Negative charges on the TIM23 act as a receptor for the incoming precursor, pulling the positively charged matrix-targeting sequence for peptide insertion and translocation.
Transport of mitochondrial precursors across the TIM23 channel is driven by...
Translocation of Proteins into the Mitochondria01:19

Translocation of Proteins into the Mitochondria

Mitochondrial precursors are translocated to the internal subcompartments via independent mechanisms involving distinct protein machineries called translocases.
Sorting of outer membrane proteins:
Mitochondrial outer membrane proteins are of two types: the transmembrane, beta-barrel porins, and the membrane-anchored, alpha-helical proteins. Beta-barrel porin precursors are translocated by the TOM complex and inserted into the outer mitochondrial membrane by the SAM complex. In contrast,...
Toxoplasmosis01:28

Toxoplasmosis

Toxoplasmosis, a zoonotic disease caused by the protozoan Toxoplasma gondii, poses significant public health challenges globally due to its high seroprevalence and varied clinical manifestations. As an obligate intracellular parasite, T. gondii can infect all warm-blooded vertebrates, but felids are its only definitive hosts, shedding unsporulated oocysts into the environment. Humans typically acquire the infection through ingestion of tissue cysts in undercooked meat or oocysts from...
Energy to Drive Translocation01:37

Energy to Drive Translocation

Mitochondrial protein import is powered by two distinct energy sources: ATP hydrolysis and electrochemical potential across the inner membrane. Newly synthesized precursors are bound by cytosolic chaperones of the Hsp70 family, which guide them to the import receptors on the mitochondrial surface. Utilizing the energy of ATP hydrolysis, Hsp70 chaperones transfer these precursors to the TOM receptors on the mitochondrial outer membrane.
Generally, polypeptides are unfolded by two distinct...