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Related Concept Videos

Initiation of Translation02:33

Initiation of Translation

Initiating translation is complex because it involves multiple molecules. Initiator tRNA, ribosomal subunits, and eukaryotic initiation factors (eIFs) are all required to assemble on the initiation codon of mRNA. This process consists of several steps that are mediated by different eIFs.
First, the initiator tRNA must be selected from the pool of elongator tRNAs by eukaryotic initiation factor 2 (eIF2). The initiator tRNA (Met-tRNAi) has conserved sequence elements including modified bases at...
Initiation of Translation02:33

Initiation of Translation

Initiating translation is complex because it involves multiple molecules. Initiator tRNA, ribosomal subunits, and eukaryotic initiation factors (eIFs) are all required to assemble on the initiation codon of mRNA. This process consists of several steps that are mediated by different eIFs.
First, the initiator tRNA must be selected from the pool of elongator tRNAs by eukaryotic initiation factor 2 (eIF2). The initiator tRNA (Met-tRNAi) has conserved sequence elements including modified bases at...
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...
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,...
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...
Porin Insertion in the Outer Mitochondrial Membrane01:12

Porin Insertion in the Outer Mitochondrial Membrane

Porins are beta-barrel proteins translocated to the mitochondrial outer membrane through the TOM complex into the intermembrane space. Porin precursors bind TIM chaperones within the intermembrane space and are guided to the Sorting and Assembly Machinery complex or SAM complex on the outer mitochondrial membrane.
Three models describe the assembly of porins by the SAM complex and their insertion into the outer membrane. Model 1 suggests that porins are assembled outside the SAM channel as the...

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Related Experiment Video

Updated: May 8, 2026

Mitochondrial Transformation in Baker's Yeast to Study Translation and Respiratory Complex Assembly
09:53

Mitochondrial Transformation in Baker's Yeast to Study Translation and Respiratory Complex Assembly

Published on: June 7, 2024

Mitochondrial translation initiation machinery: conservation and diversification.

Anton Kuzmenko1, Gemma C Atkinson2, Sergey Levitskii3

  • 1University of Tartu, Institute of Technology, Nooruse 1, Tartu, Estonia; Molecular Biology Department, Faculty of Biology, M.V. Lomonosov Moscow State University, 1/12 Leninskie Gory, 119991 Moscow, Russia.

Biochimie
|August 20, 2013
PubMed
Summary

Mitochondria use unique proteins to initiate translation, differing from bacterial ancestors. This review details these factors, highlighting diverse mechanisms across eukaryotes for respiratory chain assembly.

Keywords:
IF2IF3MitochondriaRibosomeTranslational activators

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Last Updated: May 8, 2026

Mitochondrial Transformation in Baker's Yeast to Study Translation and Respiratory Complex Assembly
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Area of Science:

  • Mitochondrial biology
  • Molecular genetics
  • Protein synthesis

Background:

  • Mitochondrial genomes encode essential respiratory chain components.
  • Correct assembly requires precise stoichiometry and membrane insertion of these proteins.
  • The mitochondrial translational system faces unique challenges in producing these components.

Purpose of the Study:

  • To review the proteins involved in mitochondrial translation initiation.
  • To describe both general and specific initiation factors.
  • To explore the evolutionary divergence and diversity of mitochondrial translation initiation.

Main Methods:

  • Literature review of mitochondrial translation initiation.
  • Analysis of bacterial-like and mitochondria-specific initiation factors.
  • Comparative study of eukaryotic mitochondrial translation systems.

Main Results:

  • Mitochondrial translation initiation involves bacterial-like factors (mIF2, mIF3) and mitochondria-specific activators and accessory factors.
  • These factors ensure the correct production and membrane insertion of respiratory chain components.
  • Significant evolutionary divergence from bacterial systems and high diversity among eukaryotes are observed.

Conclusions:

  • Mitochondrial translation initiation is orchestrated by a complex set of proteins.
  • Evolutionary pressures have led to lineage-specific mechanisms in eukaryotes.
  • Understanding these mechanisms is crucial for comprehending mitochondrial function and biogenesis.