Related Experiment Video
Updated: Aug 7, 2026
10:31
A Model Membrane Platform for Reconstituting Mitochondrial Membrane Dynamics
Published on: September 2, 2020
How membrane proteins travel across the mitochondrial intermembrane space
C M Koehler1, S Merchant, G Schatz
1Dept of Biochemistry, Biozentrum, University of Basel, CH-4056 Basel, Switzerland.
Trends in Biochemical Sciences
|November 5, 1999
Summary
Researchers found new small proteins in yeast mitochondria that help import proteins. Losing a similar protein in humans causes deafness, muscle weakness, and blindness.
Area of Science:
- Mitochondrial biology
- Protein import
- Human genetics
Background:
- Mitochondria are vital organelles with complex protein import systems.
- The mitochondrial intermembrane space (IMS) plays a role in protein transport.
- Dysfunctional mitochondrial protein import is linked to various human diseases.
Purpose of the Study:
- To identify and characterize novel proteins involved in mitochondrial protein import in yeast.
- To investigate the function of these proteins in the import of hydrophobic proteins into the inner mitochondrial membrane.
- To explore the link between these proteins and human mitochondrial diseases.
Main Methods:
- Yeast genetics and molecular biology techniques were employed.
- Protein import assays were performed using hydrophobic substrates.
- Human mitochondrial genetics and patient data were analyzed.
Main Results:
- A new family of small proteins in the yeast IMS was discovered.
- These proteins were shown to mediate the import of hydrophobic proteins into the inner mitochondrial membrane.
- Loss of a homologous protein in human mitochondria leads to a disease characterized by deafness, muscle weakness, and blindness.
Conclusions:
- This newly identified protein family is crucial for mitochondrial protein import in yeast.
- These findings highlight a conserved mechanism for mitochondrial protein targeting.
- Defects in these proteins represent a potential cause of inherited human mitochondrial disorders.
Related Concept Videos
01:45Mitochondrial Membranes
A single mitochondrion is a bean-shaped organelle enclosed by a double-membrane system. The outer membrane of mitochondria is smooth and contains many porins - the integral membrane transporters. Porins enable free diffusion of ions and small uncharged molecules through the outer mitochondrial membrane but limit the transport of molecules larger than 5000 Daltons. Further, the outer mitochondrial membrane forms a unique structure called membrane contact sites with other subcellular organelles,...
01:39Mitochondrial 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...
Most of these mitochondrial proteins are encoded by the nucleus and imported to the mitochondria as unfolded or loosely folded precursors. Mitochondrial precursors...
01:19Translocation 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,...
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,...
01:37Energy 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...
Generally, polypeptides are unfolded by two distinct...
01:34Protein 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...
Transport of mitochondrial precursors across the TIM23 channel is driven by...
01:45Mitochondrial Membranes
A single mitochondrion is a bean-shaped organelle enclosed by a double-membrane system. The outer membrane of mitochondria is smooth and contains many porins - the integral membrane transporters. Porins enable free diffusion of ions and small uncharged molecules through the outer mitochondrial membrane but limit the transport of molecules larger than 5000 Daltons. Further, the outer mitochondrial membrane forms a unique structure called membrane contact sites with other subcellular organelles,...