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Related Concept Videos

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,...
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...
Structure of Porins01:21

Structure of Porins

Mitochondria, chloroplasts, and gram-negative bacteria have transmembrane, beta-barrel proteins called porins to mediate the free diffusion of ions and metabolites across the membrane. Mitochondrial porin precursors contain conserved amino acid sequences called beta signals at their C-terminal. Beta signals have a  motif of PoXGXXHyXHy (Po-Polar, X-Any amino acid, G-Glycine, Hy-LargeHydrophobic), which are crucial for precursor recognition to initiate precursor assembly. Beta-barrel precursors...
Animal Mitochondrial Genetics02:59

Animal Mitochondrial Genetics

Among all the organelles in an animal cell, only mitochondria have their own independent genomes. Animal mitochondrial DNA is a double-stranded, closed-circular molecule with around 20,000 base pairs. Mitochondrial DNA is unique in that one of its two strands, the heavy, or H, -strand is guanine rich, whereas the complementary strand is cytosine rich and called the light, or L, -strand. Compared to nuclear DNA, mitochondrial DNA has a very low percentage of non-coding regions and is marked by...
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...

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Related Experiment Video

Updated: Jul 10, 2026

Measurement of Protein Import Capacity of Skeletal Muscle Mitochondria
09:01

Measurement of Protein Import Capacity of Skeletal Muscle Mitochondria

Published on: January 7, 2022

How do mammalian mitochondria synthesize proteins?

J Rorbach1, R Soleimanpour-Lichaei, R N Lightowlers

  • 1Mitochondria Research Group, Department of Neurology, Newcastle University, Medical School, Framlington Place, Newcastle upon Tyne NE2 4HH, U.K. joanna.rorbach@ncl.ac.uk

Biochemical Society Transactions
|October 25, 2007
PubMed
Summary

Human mitochondria use their own genome, with nuclear factors aiding protein translation. This review details the complex mechanisms and key players in mitochondrial protein synthesis.

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Last Updated: Jul 10, 2026

Measurement of Protein Import Capacity of Skeletal Muscle Mitochondria
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Isolation and Functional Analysis of Mitochondria from Cultured Cells and Mouse Tissue
09:27

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Rapid Isolation of the Mitoribosome from HEK Cells

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Area of Science:

  • Cell Biology
  • Molecular Biology
  • Genetics

Background:

  • Mitochondria possess a unique genome distinct from the nuclear genome.
  • Mitochondrial gene expression relies on imported nuclear-encoded proteins.
  • Understanding mitochondrial protein synthesis is crucial for cellular function.

Purpose of the Study:

  • To review the current understanding of protein translation in human mitochondria.
  • To identify and describe the factors involved in this organellar process.

Main Methods:

  • Literature review of existing research on mitochondrial translation.
  • Synthesis of current knowledge on the molecular machinery and regulation.

Main Results:

  • Detailed overview of the mitochondrial ribosome and its components.
  • Identification of key protein factors essential for initiation, elongation, and termination.
  • Discussion of the unique aspects of mitochondrial translation compared to cytoplasmic systems.

Conclusions:

  • Mitochondrial protein translation is a complex, tightly regulated process.
  • Nuclear-encoded factors play indispensable roles in organellar protein synthesis.
  • Further research into mitochondrial translation mechanisms can reveal insights into diseases.