Related Experiment Video
Updated: Jun 3, 2026
14:44
Isolation of mRNAs Associated with Yeast Mitochondria to Study Mechanisms of Localized Translation
Published on: March 14, 2014
Mitochondrial tRNA import and its consequences for mitochondrial translation
1Department of Chemistry and Biochemistry, University of Bern, CH-3012 Bern, Switzerland. andre.schneider@ibc.unibe.ch
Annual Review of Biochemistry
|March 23, 2011
Summary
Eukaryotes import cytosolic transfer RNAs (tRNAs) into mitochondria to compensate for missing genes. These imported tRNAs, crucial for mitochondrial function, require unique evolutionary adaptations for integration.
Area of Science:
- Mitochondrial biology
- Molecular genetics
- Evolutionary biology
Background:
- Mitochondrial genomes often lack tRNA genes, necessitating tRNA import from the cytosol.
- Cytosolic tRNAs are essential for mitochondrial protein synthesis in many eukaryotes.
Purpose of the Study:
- To elucidate the mechanisms of tRNA import into mitochondria.
- To understand the functional integration of imported tRNAs into the mitochondrial translation system.
Main Methods:
- Comparative analysis of tRNA import mechanisms across different eukaryotic systems (yeast, plants, protozoa).
- Investigation of the role of protein import pathways in tRNA translocation.
- Examination of evolutionary adaptations for tRNA integration.
Main Results:
- Two primary tRNA import mechanisms exist: co-import with precursor proteins (e.g., yeast tRNA(Lys)) and direct import (plants, protozoa).
- Direct tRNA import in plants may still involve components of the protein import machinery.
- All imported tRNAs are of eukaryotic origin but must adapt to the bacterial-like mitochondrial translation system.
Conclusions:
- Mitochondrial tRNA import is a conserved yet adaptable process essential for eukaryotic life.
- Evolutionary solutions are required to ensure the functional compatibility of imported tRNAs with mitochondrial translation.
- Understanding these mechanisms provides insights into organelle biogenesis and evolution.
Related Concept Videos
01:39Mitochondrial 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...
Most of the mitochondrial precursors...
01:31Translation
Lesson: Translation
Translation is the process of synthesizing proteins from the genetic information carried by messenger RNA (mRNA). Following transcription, it constitutes the final step in the expression of genes. This process is carried out by ribosomes, complexes of protein and specialized RNA molecules. Ribosomes, transfer RNA (tRNA), and other proteins produce a chain of amino acids—the polypeptide—as the end product of translation.
Translation Produces the Building Blocks of Life
Translation is the process of synthesizing proteins from the genetic information carried by messenger RNA (mRNA). Following transcription, it constitutes the final step in the expression of genes. This process is carried out by ribosomes, complexes of protein and specialized RNA molecules. Ribosomes, transfer RNA (tRNA), and other proteins produce a chain of amino acids—the polypeptide—as the end product of translation.
Translation Produces the Building Blocks of Life
01:31Translation
Lesson: Translation
Translation is the process of synthesizing proteins from the genetic information carried by messenger RNA (mRNA). Following transcription, it constitutes the final step in the expression of genes. This process is carried out by ribosomes, complexes of protein and specialized RNA molecules. Ribosomes, transfer RNA (tRNA), and other proteins produce a chain of amino acids—the polypeptide—as the end product of translation.
Translation Produces the Building Blocks of Life
Translation is the process of synthesizing proteins from the genetic information carried by messenger RNA (mRNA). Following transcription, it constitutes the final step in the expression of genes. This process is carried out by ribosomes, complexes of protein and specialized RNA molecules. Ribosomes, transfer RNA (tRNA), and other proteins produce a chain of amino acids—the polypeptide—as the end product of translation.
Translation Produces the Building Blocks of Life
01:19Translocation 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,...
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,...
01:39Mitochondrial 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...
Most of these mitochondrial proteins are encoded by the nucleus and imported to the mitochondria as unfolded or loosely folded precursors. Mitochondrial precursors...
01:34Protein 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...
Transport of mitochondrial precursors across the TIM23 channel is driven by...