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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,...
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...
Energy to Drive Translocation01:37

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...
The Inner Mitochondrial Membrane01:28

The Inner Mitochondrial Membrane

The inner mitochondrial membrane is the primary site of ATP synthesis. The inner membrane domain that forms a smooth layer adjacent to the outer membrane is called the inner boundary membrane. This domain contains membrane transporters that drive metabolites in and out of the mitochondria.  In contrast, the inner membrane network that invaginates into the matrix space is called the cristae membrane. This domain accounts for principle mitochondrial function as it accommodates the protein...
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...

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Related Experiment Video

Updated: Jun 1, 2026

Reconstitution of Msp1 Extraction Activity with Fully Purified Components
05:52

Reconstitution of Msp1 Extraction Activity with Fully Purified Components

Published on: August 10, 2021

High-mobility group box 1 is essential for mitochondrial quality control.

Daolin Tang1, Rui Kang, Kristen M Livesey

  • 1Department of Surgery, G.27A Hillman Cancer Center, University of Pittsburgh Cancer Institute, Pittsburgh, PA 15219, USA.

Cell Metabolism
|June 7, 2011
PubMed
Summary

High-mobility group box 1 (HMGB1) regulates mitochondrial function and morphology through heat shock protein beta-1 (HSPB1). HMGB1 and HSPB1 are crucial for cellular defense against mitochondrial stress and maintaining quality control via autophagy.

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An Improved Method to Isolate Mitochondrial Contact Sites
07:55

An Improved Method to Isolate Mitochondrial Contact Sites

Published on: June 16, 2023

Related Experiment Videos

Last Updated: Jun 1, 2026

Reconstitution of Msp1 Extraction Activity with Fully Purified Components
05:52

Reconstitution of Msp1 Extraction Activity with Fully Purified Components

Published on: August 10, 2021

An Improved Method to Isolate Mitochondrial Contact Sites
07:55

An Improved Method to Isolate Mitochondrial Contact Sites

Published on: June 16, 2023

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Biochemistry

Background:

  • Mitochondria are vital for cellular energy production and apoptosis.
  • High-mobility group box 1 (HMGB1) is a nuclear protein regulating homeostasis and mitochondrial function.
  • Heat shock protein beta-1 (HSPB1/HSP27) is implicated in cellular stress responses.

Purpose of the Study:

  • To elucidate the role of HMGB1 in mitochondrial regulation.
  • To identify downstream mediators of HMGB1's mitochondrial effects.
  • To investigate the connection between HMGB1, HSPB1, and cellular stress response.

Main Methods:

  • Gene disruption and forced expression in embryonic fibroblasts.
  • Analysis of mitochondrial morphology and function (respiration, ATP synthesis).
  • Assessment of autophagic processes and mitochondrial quality control.

Main Results:

  • Disruption of HSPB1 mimicked mitochondrial defects seen in HMGB1 knockout cells.
  • Forced HSPB1 expression rescued mitochondrial phenotypes in HMGB1-deficient cells.
  • HMGB1 regulates HSPB1 expression, impacting mitochondrial health during stress.

Conclusions:

  • HSPB1 is a key downstream mediator of HMGB1's mitochondrial effects.
  • HMGB1-mediated HSPB1 regulation is essential for mitochondrial quality control.
  • HMGB1 plays a critical role in autophagic surveillance of mitochondria under stress.