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Related Concept Videos

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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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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Translocation of Proteins into the Mitochondria01:19

Translocation of Proteins into the Mitochondria

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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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Porin Insertion in the Outer Mitochondrial Membrane01:12

Porin Insertion in the Outer Mitochondrial Membrane

4.1K
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...
4.1K
Protein Transport into the Inner Mitochondrial Membrane01:34

Protein Transport into the Inner Mitochondrial Membrane

4.5K
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...
4.5K
Energy to Drive Translocation01:37

Energy to Drive Translocation

2.5K
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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Related Experiment Video

Updated: Nov 29, 2025

Assessment of Submitochondrial Protein Localization in Budding Yeast Saccharomyces cerevisiae
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Assessment of Submitochondrial Protein Localization in Budding Yeast Saccharomyces cerevisiae

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Identification of Putative Mitochondrial Protease Substrates.

Eduard Hofsetz1,2, Pitter F Huesgen3, Aleksandra Trifunovic4,5

  • 1Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, Cologne, Germany.

Methods in Molecular Biology (Clifton, N.J.)
|November 24, 2020
PubMed
Summary

Mitochondrial proteases remove damaged proteins. New methods identify substrates and products of complete or partial proteolysis, improving protein quality control understanding.

Keywords:
ImmunoprecipitationsMitochondriaN Termini profilingProteasesProteolysisSubstrate-trappingSubstratesTAILS

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Area of Science:

  • Mitochondrial biology
  • Proteomics
  • Protein quality control

Background:

  • Mitochondrial proteases are crucial for removing damaged proteins within organelles.
  • Current methods primarily identify substrates that are fully degraded, overlooking partial processing.
  • Proteolytic processing can alter protein function, impacting cellular activities.

Purpose of the Study:

  • To adapt existing methods for comprehensive analysis of mitochondrial protease substrates.
  • To identify proteins undergoing both complete degradation and partial processing by mitochondrial proteases.
  • To enhance the understanding of mitochondrial protein quality control mechanisms.

Main Methods:

  • Adaptation of the substrate-trapping technique.
  • Application of N-terminal profiling using Terminal Amine Isotope Labeling of Substrates (TAILS).
  • Combined approaches for identifying bona fide substrates and proteolytic products.

Main Results:

  • Successfully identified bona fide substrates of mitochondrial proteases.
  • Detected mitochondrial proteins that are partially proteolyzed, yielding shortened forms.
  • The adapted methods provide a broader view of protease activity beyond complete degradation.

Conclusions:

  • The developed methods offer a more comprehensive analysis of mitochondrial protease functions.
  • Partial proteolysis is a significant aspect of mitochondrial protein processing.
  • This research advances the study of mitochondrial protein homeostasis and quality control.