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Related Concept Videos

Translocation of Proteins into the Mitochondria01:19

Translocation of Proteins into the Mitochondria

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,...
Protein Transport into the Inner Mitochondrial Membrane01:34

Protein Transport into the Inner Mitochondrial Membrane

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...
Mitochondrial Protein Sorting01:39

Mitochondrial Protein Sorting

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...
Mitochondrial Precursor Proteins01:39

Mitochondrial Precursor Proteins

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 precursors...
Porin Insertion in the Outer Mitochondrial Membrane01:12

Porin Insertion in the Outer Mitochondrial Membrane

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...
Protein Transport to the Inner Chloroplast Membrane01:18

Protein Transport to the Inner Chloroplast Membrane

Proteins targeted to the inner chloroplast membrane, or plastid proteins, are transported by two general pathways: the stop-transfer and the re-insertion or post-import pathways. Most plastid proteins carry N-terminal transit sequences and internal import sequences targeting it to the specific chloroplast subcompartment. Proteins targeted by the stop-transfer pathway have internal hydrophobic sequences that inhibit their translocation into the stroma. As a result, these precursors are arrested...

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Related Experiment Video

Updated: Jul 14, 2026

Measurement of Protein Import Capacity of Skeletal Muscle Mitochondria
09:01

Measurement of Protein Import Capacity of Skeletal Muscle Mitochondria

Published on: January 7, 2022

[Directed import of macromolecules into mitochondria].

P A Kamenskiĭ, E N Vinogradova, I A Krasheninnikov

    Molekuliarnaia Biologiia
    |May 23, 2007
    PubMed
    Summary

    Mitochondria import proteins and small RNAs from the cytoplasm. While protein import mechanisms are conserved, RNA import pathways vary across eukaryotic organisms, requiring further investigation.

    Area of Science:

    • Cell Biology
    • Molecular Biology
    • Organelle Biology

    Background:

    • Mitochondria are vital eukaryotic organelles involved in energy production, apoptosis, and metabolic processes.
    • They possess their own genome but rely on cytoplasmic import for most functional macromolecules.
    • Key imported macromolecules include proteins and various small RNAs.

    Purpose of the Study:

    • To review and summarize the current knowledge on macromolecule import into mitochondria.
    • To highlight the differences and similarities between protein and RNA import mechanisms.
    • To discuss the non-universal nature of RNA import pathways in eukaryotes.

    Main Methods:

    • Literature review of existing studies on mitochondrial import.
    • Comparative analysis of protein and RNA import mechanisms.

    More Related Videos

    Studying Protein Import into Chloroplasts Using Protoplasts
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    Studying Protein Import into Chloroplasts Using Protoplasts

    Published on: December 10, 2018

    Experimental Approaches to Study Mitochondrial Localization and Function of a Nuclear Cell Cycle Kinase, Cdk1
    13:15

    Experimental Approaches to Study Mitochondrial Localization and Function of a Nuclear Cell Cycle Kinase, Cdk1

    Published on: February 25, 2016

    Related Experiment Videos

    Last Updated: Jul 14, 2026

    Measurement of Protein Import Capacity of Skeletal Muscle Mitochondria
    09:01

    Measurement of Protein Import Capacity of Skeletal Muscle Mitochondria

    Published on: January 7, 2022

    Studying Protein Import into Chloroplasts Using Protoplasts
    06:29

    Studying Protein Import into Chloroplasts Using Protoplasts

    Published on: December 10, 2018

    Experimental Approaches to Study Mitochondrial Localization and Function of a Nuclear Cell Cycle Kinase, Cdk1
    13:15

    Experimental Approaches to Study Mitochondrial Localization and Function of a Nuclear Cell Cycle Kinase, Cdk1

    Published on: February 25, 2016

  • Synthesis of data on the diversity of imported RNA molecules and their import pathways.

    • Main Results:

    • Protein import into mitochondria is a universal and well-understood process.
    • RNA import occurs in diverse eukaryotic groups, with varying pools of imported RNAs.
    • Mechanisms for RNA import are not conserved across all species that exhibit this process.

    Conclusions:

    • Mitochondrial import of macromolecules is essential for cellular function.
    • Understanding RNA import mechanisms is crucial due to their variability and importance.
    • Further research is needed to elucidate the specific, non-universal pathways of RNA import into mitochondria.