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Related Concept Videos

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...
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...
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...
Mitochondrial Membranes01:45

Mitochondrial Membranes

A single mitochondrion is a bean-shaped organelle enclosed by a double-membrane system. The outer membrane of mitochondria is smooth and contains many porins - the integral membrane transporters. Porins enable free diffusion of ions and small uncharged molecules through the outer mitochondrial membrane but limit the transport of molecules larger than 5000 Daltons. Further, the outer mitochondrial membrane forms a unique structure called membrane contact sites with other subcellular organelles,...
Mitochondrial Membranes01:45

Mitochondrial Membranes

A single mitochondrion is a bean-shaped organelle enclosed by a double-membrane system. The outer membrane of mitochondria is smooth and contains many porins - the integral membrane transporters. Porins enable free diffusion of ions and small uncharged molecules through the outer mitochondrial membrane but limit the transport of molecules larger than 5000 Daltons. Further, the outer mitochondrial membrane forms a unique structure called membrane contact sites with other subcellular organelles,...

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Mitochondrial uncoupling proteins in unicellular eukaryotes.

Wieslawa Jarmuszkiewicz1, Andrzej Woyda-Ploszczyca, Nina Antos-Krzeminska

  • 1Laboratory of Bioenergetics, Faculty of Biology, Adam Mickiewicz University, Umultowska 89, 61-614 Poznan, Poland. wiesiaj@amu.edu.pl

Biochimica Et Biophysica Acta
|December 23, 2009
PubMed
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Uncoupling proteins (UCPs) regulate energy balance in unicellular eukaryotes by uncoupling proton flow from ATP synthesis. Reduced ubiquinone (Q) may control UCP activity, impacting cellular energy and reactive oxygen species production.

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Area of Science:

  • Mitochondrial physiology
  • Cellular respiration
  • Biochemistry

Background:

  • Uncoupling proteins (UCPs) are mitochondrial inner membrane proteins.
  • UCPs facilitate FFA-activated, PN-inhibited proton conductance.
  • UCPs are found in unicellular eukaryotes like protists, yeast, and fungi.

Purpose of the Study:

  • To investigate the role of UCPs in unicellular eukaryotes.
  • To explore the regulatory mechanism of UCP activity by ubiquinone (Q).
  • To discuss the functional connection between UCPs and alternative oxidase in energy dissipation.

Main Methods:

  • Analysis of mitochondrial respiration and membrane potential.
  • Assessment of ubiquinone reduction levels.
  • Comparative study across different UCPs (unicellular, plant, mammalian).

Main Results:

  • UCP activity in unicellular eukaryotes diverts energy from oxidative phosphorylation.
  • Membranous ubiquinone (Q) acts as a metabolic sensor.
  • Reduced ubiquinone (QH2) may release purine nucleotide (PN) inhibition of UCPs.
  • This regulation is conserved across various UCPs.

Conclusions:

  • UCPs and alternative oxidase are key energy-dissipating systems in unicellular eukaryotes.
  • UCP regulation by Q impacts cellular energy balance.
  • This mechanism may prevent reactive oxygen species production.