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Related Concept Videos

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...
Export of Mitochondrial and Chloroplast Genes02:19

Export of Mitochondrial and Chloroplast Genes

A eukaryotic cell can have up to three different types of genetic systems: nuclear, mitochondrial, and chloroplast. During evolution, organelles have exported many genes to the nucleus; this transfer is still ongoing in some plant species. Approximately 18% of the Arabidopsis thaliana nuclear genome is thought to be derived from the chloroplast’s cyanobacterial ancestor, and around 75% of the yeast genome derived from the mitochondria’s bacterial ancestor. This export has occurred irrespective...
ATP Synthase: Mechanism01:48

ATP Synthase: Mechanism

In animals, the mitochondrial F1F0 ATP synthase is the key protein that synthesizes ATP molecules through a complex catalytic mechanism. While the nuclear genome encodes the majority of ATP synthase subunits, the mitochondrial genome encodes some of the enzyme's most critical components. The formation of this multi-subunit enzyme is a complex multi-step process regulated at the level of transcription, translation, and assembly. Defects in one or more of these steps can result in decreased ATP...
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...
Electron Transport Chain: Complex I and II01:46

Electron Transport Chain: Complex I and II

The mitochondrial electron transport chain (ETC) is the main energy generation system in the eukaryotic cells. However, mitochondria also produce cytotoxic reactive oxygen species (ROS) due to the large electron flow during oxidative phosphorylation. While Complex I is one of the primary sources of superoxide radicals, ROS production by Complex II is uncommon and may only be observed in cancer cells with mutated complexes.
ROS generation is regulated and maintained at moderate levels necessary...
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...

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An In Vitro Approach to Study Mitochondrial Dysfunction: A Cybrid Model
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Functional complementation of mitochondrial DNAs: mobilizing mitochondrial genetics against dysfunction.

Eric A Schon1, Robert W Gilkerson

  • 1Department of Neurology, College of Physicians and Surgeons, Columbia University, Russ Berrie Pavilion 307, 1150 St. Nicholas Ave., New York, NY 10032, USA.

Biochimica Et Biophysica Acta
|July 21, 2009
PubMed
Summary
This summary is machine-generated.

Mitochondrial DNA (mtDNA) heteroplasmy, where cells contain both wildtype (WT) and mutant mtDNA, can be functionally restored. Mutant and WT mtDNA populations transcomplement each other within nucleoids, maintaining mitochondrial function.

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Area of Science:

  • Cell Biology
  • Genetics
  • Molecular Biology

Background:

  • Human cells contain thousands of mitochondrial DNA (mtDNA) copies.
  • Heteroplasmy occurs when cells harbor both wildtype (WT) and mutant mtDNA variants.
  • The functional interactions between different mtDNA populations within a cell remain poorly understood.

Purpose of the Study:

  • To investigate the submitochondrial organization and functional interactions of mtDNA heteroplasmy within nucleoids.
  • To elucidate how different mtDNA populations cooperate to maintain cellular function.

Main Methods:

  • Utilized sequence-specific microscopic techniques for high-resolution mtDNA examination.
  • Analyzed the organization of mtDNA heteroplasmy within nucleoids (mtDNA-protein complexes).

Main Results:

  • Heterologous mtDNA variants were found to be stably maintained in separate nucleoid populations.
  • Despite separation, different mtDNA types transcomplement each other to restore WT-like mitochondrial function and morphology.
  • Diffusion of mtDNA transcripts facilitates this transcomplementation across the mitochondrial network.

Conclusions:

  • Nucleoids maintain genetic autonomy, but mtDNA populations functionally interact via transcript diffusion.
  • mtDNA transcomplementation offers a potential therapeutic strategy for heteroplasmic conditions.
  • Mitochondrial fission/fusion dynamics and nucleoid organization are linked to mtDNA heteroplasmy management.