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Related Concept Videos

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

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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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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

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
Structure of Porins01:21

Structure of Porins

4.1K
Mitochondria, chloroplasts, and gram-negative bacteria have transmembrane, beta-barrel proteins called porins to mediate the free diffusion of ions and metabolites across the membrane. Mitochondrial porin precursors contain conserved amino acid sequences called beta signals at their C-terminal. Beta signals have a  motif of PoXGXXHyXHy (Po-Polar, X-Any amino acid, G-Glycine, Hy-LargeHydrophobic), which are crucial for precursor recognition to initiate precursor assembly. Beta-barrel...
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Related Experiment Video

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Measurement of Protein Import Capacity of Skeletal Muscle Mitochondria
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[Mitochondrial protein import complexes - a phylogenetic perspective].

Małgorzata Wojtkowska1, Hanna Kmita1

  • 1Laboratory of Bioenergetics, Institute of Molecular Biology and Biotechnology, Faculty of Biology, Adam Mickiewicz University in Poznan, 89 Umultowska St., 61-614 Poznan, Poland.

Postepy Biochemii
|January 30, 2017
PubMed
Summary

Mitochondrial protein import complexes are crucial for eukaryotic cell function. Their organization varies across eukaryotes, especially the TOM complex, offering insights into mitochondria evolution and applications.

Keywords:
eukaryotic lineagesimport complexesprotein import into mitochondria

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Area of Science:

  • Mitochondrial biology
  • Cellular and molecular biology
  • Evolutionary biology

Background:

  • Mitochondria are vital organelles in eukaryotic cells, requiring efficient protein import for proper function.
  • Protein import into mitochondria is mediated by sophisticated protein complexes located in all mitochondrial compartments.
  • Understanding the organization of these import complexes is key to comprehending mitochondrial biogenesis and evolution.

Purpose of the Study:

  • To compile and analyze data on the organization of mitochondrial protein import complexes across diverse eukaryotic lineages.
  • To investigate variations in the structure and composition of these complexes, particularly the TOM complex.
  • To explore the evolutionary implications of observed organizational differences and potential practical applications.

Main Methods:

  • Data collection and comparative analysis of mitochondrial import complex organization.
  • Focus on the Translocase of the Outer mitochondrial membrane (TOM) complex.
  • Literature review and synthesis of available data from various eukaryotic representatives.

Main Results:

  • Data on import complex organization is currently limited for many eukaryotic lineages.
  • Emerging evidence suggests significant differentiation in the organization of import complexes.
  • The TOM complex exhibits notable variations in its organization across different eukaryotes.

Conclusions:

  • The observed differentiation in import complex organization, especially the TOM complex, has significant implications for understanding mitochondria evolution.
  • Further research is needed to fully elucidate the diversity and evolution of these essential cellular machinery.
  • The findings may hold potential for future practical applications in biotechnology or medicine.