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Related Concept Videos

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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Mitochondrial Protein Sorting01:39

Mitochondrial Protein Sorting

5.9K
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...
5.9K
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,...
13.6K
Mitochondrial Precursor Proteins01:39

Mitochondrial Precursor Proteins

3.9K
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...
3.9K
Energy to Drive Translocation01:37

Energy to Drive Translocation

2.9K
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...
2.9K
Porin Insertion in the Outer Mitochondrial Membrane01:12

Porin Insertion in the Outer Mitochondrial Membrane

5.1K
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...
5.1K

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Related Experiment Video

Updated: Mar 15, 2026

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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The TIM23 mitochondrial protein import complex: function and dysfunction.

Keren Demishtein-Zohary1, Abdussalam Azem2

  • 1Department of Biochemistry and Molecular Biology, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, 69978, Israel.

Cell and Tissue Research
|September 4, 2016
PubMed
Summary
This summary is machine-generated.

The TIM23 complex is crucial for mitochondrial protein import, acting as a channel and motor for matrix proteins. Recent research illuminates its mammalian function and role in disease.

Keywords:
Import motorMitochondrial protein importPam complexTIM23 complexTOM complex

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Area of Science:

  • Mitochondrial Biology
  • Molecular Cell Biology

Background:

  • Mitochondria import most proteins from the cytosol via complex machinery.
  • The TIM23 complex is a key translocase for mitochondrial matrix proteins.

Purpose of the Study:

  • To review the components and functions of the TIM23 complex.
  • To highlight recent insights into mammalian TIM23 complex function and its role in pathology.

Main Methods:

  • Literature review of studies on yeast and mammalian TIM23 complex.
  • Analysis of protein components and their functional categorization.

Main Results:

  • TIM23 complex components are categorized into receptors, channel formers, motor elements, and regulators.
  • Recent studies offer new perspectives on mammalian TIM23 complex function.

Conclusions:

  • The TIM23 complex is essential for mitochondrial protein import, with diverse functional subunits.
  • Understanding the mammalian TIM23 complex is vital for comprehending its role in disease states.