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Related Concept Videos

Translocation of Proteins into the Mitochondria01:19

Translocation of Proteins into the Mitochondria

13.6K
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,...
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Mitochondrial Protein Sorting01:39

Mitochondrial Protein Sorting

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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...
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Mitochondrial Precursor Proteins01:39

Mitochondrial Precursor Proteins

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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...
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Protein Transport into the Inner Mitochondrial Membrane01:34

Protein Transport into the Inner Mitochondrial Membrane

5.1K
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...
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Porin Insertion in the Outer Mitochondrial Membrane01:12

Porin Insertion in the Outer Mitochondrial Membrane

5.0K
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...
5.0K
Export of Misfolded Proteins out of the ER01:32

Export of Misfolded Proteins out of the ER

5.4K
After folding, the ER assesses the quality of secretory and membrane proteins. The correctly folded proteins are cleared by the calnexin cycle for transport to their final destination, while misfolded proteins are held back in the ER lumen. The ER chaperones attempt to unfold and refold the misfolded proteins but sometimes fail to achieve the correct native conformation. Such terminally misfolded proteins are then exported to the cytosol by ER-associated degradation or ERAD pathway for...
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Related Experiment Video

Updated: Mar 8, 2026

Measurement of Protein Import Capacity of Skeletal Muscle Mitochondria
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Measurement of Protein Import Capacity of Skeletal Muscle Mitochondria

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[Mitochondrial proteins - import, export, degradation].

Michał Wasilewski1, Katarzyna Chojnacka1, Agnieszka Chacińska1

  • 1Laboratory of Mitochondrial Biogenesis, International Institute of Molecular and Cell Biology in Warsaw, 4 Trojdena St., 02-109 Warsaw, Poland.

Postepy Biochemii
|January 30, 2017
PubMed
Summary
This summary is machine-generated.

Mitochondria rely on nuclear DNA for over a thousand proteins essential for cellular functions. This review details how these mitochondrial proteins are synthesized, imported, and assembled, ensuring cell health.

Keywords:
mitochondriaprotein assemblyprotein degradationprotein importprotein processing

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Area of Science:

  • Cell Biology
  • Biochemistry
  • Molecular Biology

Background:

  • Mitochondria are crucial for cellular energy production, biochemical pathways, and signaling.
  • Mitochondrial proteome comprises over a thousand proteins, mostly encoded by nuclear DNA.

Purpose of the Study:

  • To review the key aspects of mitochondrial protein biogenesis.
  • To elucidate the mechanisms of mitochondrial protein synthesis, targeting, and assembly.

Main Methods:

  • Literature review of mitochondrial protein biogenesis.
  • Synthesis of information on protein targeting and translocation.
  • Analysis of protein maturation and complex assembly processes.

Main Results:

  • Mitochondrial precursor proteins are synthesized in the cytosol and imported into mitochondria.
  • Specialized translocase machineries facilitate protein targeting and sorting.
  • Protein maturation and assembly are critical for functional mitochondria.

Conclusions:

  • Mitochondrial protein biogenesis is a complex, multi-step process.
  • Efficient biogenesis and degradation are essential for maintaining mitochondrial homeostasis.
  • Understanding these processes is key to comprehending cellular function and dysfunction.