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Related Concept Videos

Translocation of Proteins into the Mitochondria01:19

Translocation of Proteins into the Mitochondria

9.2K
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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Energy to Drive Translocation01:37

Energy to Drive Translocation

2.3K
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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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...
4.9K
Protein Transport into the Inner Mitochondrial Membrane01:34

Protein Transport into the Inner Mitochondrial Membrane

4.3K
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...
4.3K
Mitochondrial Precursor Proteins01:39

Mitochondrial Precursor Proteins

3.0K
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...
3.0K
Porin Insertion in the Outer Mitochondrial Membrane01:12

Porin Insertion in the Outer Mitochondrial Membrane

3.7K
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...
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Related Experiment Video

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Measurement of Protein Import Capacity of Skeletal Muscle Mitochondria
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Accessing Mitochondrial Protein Import in Living Cells by Protein Microinjection.

Andrey Bogorodskiy1, Ivan Okhrimenko1, Ivan Maslov1

  • 1Research Center for Molecular Mechanisms of Aging and Age-Related Diseases, Moscow Institute of Physics and Technology, Dolgoprudny, Russia.

Frontiers in Cell and Developmental Biology
|July 26, 2021
PubMed
Summary

Researchers developed a gentle microinjection method to study mitochondrial protein import in living cells. This technique revealed that co-translational import is significant for mitochondrial protein biogenesis.

Keywords:
GFPSNAP-tagfluorescence microscopymicroinjectionmitochondriamitochondrial protein import

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Area of Science:

  • Cell Biology
  • Molecular Biology
  • Mitochondrial Biology

Background:

  • Mitochondrial protein biogenesis primarily relies on nuclear-encoded proteins synthesized in the cytoplasm.
  • Current understanding of mitochondrial protein import is limited by the lack of real-time experimental methods in native cellular environments.

Purpose of the Study:

  • To develop a non-invasive, real-time method for studying protein transport into mitochondria within living cells.
  • To investigate the dynamics of protein import into mitochondria and its relationship with protein synthesis.

Main Methods:

  • Developed a gentle microinjection technique for fluorescent reporter proteins into living cells.
  • Utilized puromycin to induce the release of nascent polypeptide chains from ribosomes.
  • Observed and validated mitochondrial morphology and protein translocation machinery integrity.

Main Results:

  • Successfully visualized potential-dependent protein import into mitochondria in real-time in intact cells.
  • Demonstrated that releasing nascent polypeptide chains significantly increased the import rate of microinjected pre-proteins.
  • Provided evidence for the involvement of mitochondrial translocase complexes in co-translational import.

Conclusions:

  • The microinjection method allows for direct, non-invasive study of mitochondrial protein import in living cells.
  • Co-translational import appears to be a substantial pathway for mitochondrial protein biogenesis.
  • This approach offers new avenues for studying mitochondrial protein import in disease and aging models.