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Related Concept Videos

Post-translational Translocation of Proteins to the RER01:27

Post-translational Translocation of Proteins to the RER

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A sizable fraction of proteins destined for ER are first synthesized in the cell cytosol and then transported across the ER membrane–a process called post-translational translocation. Similar to cotranslationally translocated proteins, these proteins also use the Sec translocon complex to enter the ER lumen.
Targeting proteins to the ER
Hsp40 and Hsp70 chaperone molecules bind the translated proteins in the cytosol to prevent their folding. The chaperone binding helps to keep the signal...
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Mitochondrial Protein Sorting01:39

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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.
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Eukaryotic cells have different membrane-bound organelles with distinct protein requirements. The process by which proteins are targeted to a specific organelle is called protein sorting.
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Thylakoids are membrane-bound sac-like structures within the chloroplast that serve as sites for photosynthesis. Thylakoid lumen contains many electron transport proteins and is enclosed by a thylakoid membrane rich in the light-harvesting complex. Proteins targeted to the thylakoids are transported as precursors and are sorted by the general TOC/TIC import pathway. Once the precursor reaches the stroma, stromal processing peptidases remove their transit signal and expose thylakoid signal...
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Translocation of Proteins into the Mitochondria01:19

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Mitochondrial precursors are translocated to the internal subcompartments via independent mechanisms involving distinct protein machineries called translocases.
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Translocation of proteins across membranes is an ancient process that occurs even in bacteria and archaebacteria. In fact, the components of the translocation machinery are still conserved between prokaryotes and eukaryotes.
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Related Experiment Video

Updated: Jul 31, 2025

Isolation of Physiologically Active Thylakoids and Their Use in Energy-Dependent Protein Transport Assays
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Protein transport along the presequence pathway.

Abhijith Makki1, Peter Rehling1,2,3,4

  • 1Department of Cellular Biochemistry, University Medical Center Göttingen, D-37073 Göttingen, Germany.

Biological Chemistry
|May 8, 2023
PubMed
Summary
This summary is machine-generated.

This study details mitochondrial protein import in yeast, focusing on the TIM23 complex. It explains how nuclear-encoded proteins use targeting signals for import via the TOM and TIM23 translocase complexes.

Keywords:
PAMTIM23 complexTOM complexmitochondriapresequence translocaseprotein translocation

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Area of Science:

  • Mitochondrial biology
  • Molecular cell biology
  • Protein import mechanisms

Background:

  • Most mitochondrial proteins are encoded in the nucleus and require import into the organelle.
  • Protein import relies on specific targeting signals, such as amino-terminal presequences.
  • The translocase of the outer membrane (TOM) and the TIM23 complex are key components of the presequence import pathway.

Purpose of the Study:

  • To elucidate the mechanisms of mitochondrial matrix and inner membrane protein import in Saccharomyces cerevisiae.
  • To highlight the dynamics of the TIM23 complex in protein translocation.
  • To provide an updated overview of recent advancements in the field of mitochondrial protein import.

Main Methods:

  • Review of current literature on mitochondrial protein import pathways.
  • Focus on the presequence pathway involving TOM and TIM23 complexes.
  • Analysis of the dynamics and function of the TIM23 complex in Saccharomyces cerevisiae.

Main Results:

  • Detailed description of the presequence import pathway for mitochondrial proteins.
  • Emphasis on the role and dynamics of the TIM23 complex in protein translocation across mitochondrial membranes.
  • Summary of recent key findings that have advanced understanding of mitochondrial protein import.

Conclusions:

  • The presequence pathway, mediated by TOM and TIM23, is crucial for importing many mitochondrial proteins.
  • Understanding TIM23 complex dynamics is essential for comprehending mitochondrial protein import.
  • Recent research has significantly enhanced our knowledge of these fundamental cellular processes.