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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...
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 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...
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...
Mismatch Repair01:20

Mismatch Repair

Organisms are capable of detecting and fixing nucleotide mismatches that occur during DNA replication. This sophisticated process requires identifying the new strand and replacing the erroneous bases with correct nucleotides. Mismatch repair is coordinated by many proteins in both prokaryotes and eukaryotes.
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The human genome has more than 3 billion base pairs of DNA per cell. Prior to cell division, that vast amount of genetic...

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High-Throughput Image-Based Quantification of Mitochondrial DNA Synthesis and Distribution
10:47

High-Throughput Image-Based Quantification of Mitochondrial DNA Synthesis and Distribution

Published on: May 5, 2023

mtDNA makes a U-turn for the mitochondrial nucleoid.

Christian Kukat1, Nils-Göran Larsson

  • 1Department of Mitochondrial Biology, Max Planck Institute for Biology of Ageing, Joseph-Stelzmann-Strasse 9b, 50931 Cologne, Germany.

Trends in Cell Biology
|June 1, 2013
PubMed
Summary

Mitochondrial transcription factor A (TFAM) packages mitochondrial DNA (mtDNA) into nucleoids, essential for cellular energy production. TFAM

Keywords:
TFAMmitochondrial nucleoidmtDNA

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Last Updated: May 11, 2026

High-Throughput Image-Based Quantification of Mitochondrial DNA Synthesis and Distribution
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Published on: May 5, 2023

Specific Labeling of Mitochondrial Nucleoids for Time-lapse Structured Illumination Microscopy
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Methodology for Accurate Detection of Mitochondrial DNA Methylation

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Area of Science:

  • Mitochondrial biology
  • Molecular genetics
  • Cellular energy metabolism

Background:

  • Mitochondria generate cellular energy (ATP) via oxidative phosphorylation, utilizing proteins encoded by mitochondrial DNA (mtDNA).
  • mtDNA is compacted into mitochondrial nucleoids, crucial for its organization and function within mitochondria.
  • Mitochondrial transcription factor A (TFAM) is key to mtDNA packaging and transcription initiation.

Purpose of the Study:

  • To review the structure of mitochondrial nucleoids.
  • To discuss the regulatory roles of nucleoid structure in mtDNA expression.
  • To explore the dual functions of TFAM in mtDNA packaging and transcription.

Main Methods:

  • Analysis of crystal structure of TFAM.
  • Review of super-resolution imaging studies on nucleoid structure.
  • Discussion of TFAM's role in mtDNA bending and packaging.

Main Results:

  • TFAM bends mtDNA into a sharp U-turn, explaining its dual functions.
  • Mitochondrial nucleoids average ~100nm in diameter and often contain a single mtDNA copy.
  • TFAM is essential for both mtDNA packaging into nucleoids and transcription initiation.

Conclusions:

  • The structure of TFAM, particularly its U-turn capability, underpins its role in mtDNA organization and expression.
  • Mitochondrial nucleoid structure is critical for regulating gene expression from mtDNA.
  • Further research into nucleoid structure can illuminate mechanisms of mtDNA regulation and cellular energy production.