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Translocation of Proteins into the Mitochondria

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,...

Mitochondrial Precursor Proteins

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...

Mitochondrial Protein Sorting

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...

Protein Transport into the Inner Mitochondrial Membrane

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...

Energy to Drive Translocation

Energy to Drive Translocation

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...

Porin Insertion in the Outer Mitochondrial Membrane

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...

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Related Experiment Video

Updated: Jul 5, 2026

Subcellular Fractionation for ERK Activation Upon Mitochondrial-derived Peptide Treatment

Subcellular Fractionation for ERK Activation Upon Mitochondrial-derived Peptide Treatment

Published on: September 25, 2017

Mitochondria-penetrating peptides.

Kristin L Horton¹, Kelly M Stewart, Sonali B Fonseca

¹Department of Biochemistry, Faculty of Medicine, University of Toronto, Toronto, ON M5S 3M2, Canada.

Chemistry & Biology

|April 19, 2008

Summary

This summary is machine-generated.

Scientists developed synthetic cell-permeable peptides, called mitochondria-penetrating peptides (MPPs), to deliver drugs into mitochondria. These cationic and lipophilic MPPs efficiently enter various cells, enabling targeted organelle therapies.

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Area of Science:

Biochemistry
Cell Biology
Drug Delivery

Background:

Mitochondria are key targets for cancer chemotherapy and other disease treatments.
The mitochondrial inner membrane presents a significant barrier to drug delivery.
Developing organelle-specific therapeutics requires efficient mitochondrial targeting strategies.

Purpose of the Study:

To engineer synthetic cell-permeable peptides capable of penetrating the mitochondrial membrane.
To establish a method for rationally controlling mitochondrial localization of therapeutic agents.

Main Methods:

Design and synthesis of a panel of mitochondria-penetrating peptides (MPPs).
Evaluation of MPP uptake efficiency across various cell types.
Characterization of the chemical properties (charge and lipophilicity) influencing mitochondrial entry.

Main Results:

MPPs demonstrate efficient uptake in diverse cell types.
A combination of cationic and lipophilic properties is crucial for MPP mitochondrial permeation.
Mitochondrial localization can be precisely controlled by modulating MPP lipophilicity and charge.

Conclusions:

Mitochondria-penetrating peptides (MPPs) represent a promising advancement for organelle-specific drug delivery.
The rational design of MPPs based on charge and lipophilicity enables targeted mitochondrial therapeutics.
This approach facilitates the development of novel therapeutic strategies for mitochondrial-related diseases.