Related Experiment Video
Updated: Jul 11, 2026
07:35
Assessment of Open Probability of the Mitochondrial Permeability Transition Pore in the Setting of Coenzyme Q Excess
Published on: June 1, 2022
Mrs2p forms a high conductance Mg2+ selective channel in mitochondria
Rainer Schindl1, Julian Weghuber, Christoph Romanin
1Institute for Biophysics, University of Linz, Linz, Austria.
Biophysical Journal
|September 11, 2007
Summary
The mitochondrial Mrs2 protein forms a high-conductance, magnesium-selective channel. This channel controls magnesium ion (Mg2+) influx into mitochondria via a negative feedback mechanism.
Area of Science:
- Biochemistry
- Molecular Biology
- Cell Biology
Background:
- Magnesium transporters (CorA-Mrs2-Alr1 superfamily) are essential in all life forms.
- The transport mechanism of this Mg2+ transporter family remained unclear despite structural data.
- Mitochondria play a crucial role in cellular Mg2+ homeostasis.
Purpose of the Study:
- To elucidate the ion transport mechanism of the mitochondrial Mrs2 protein.
- To characterize the ion selectivity and conductance of the Mrs2 channel.
- To investigate the regulatory mechanisms of mitochondrial Mg2+ influx.
Main Methods:
- Single channel patch-clamp electrophysiology was employed to record ion channel activity.
- Site-directed mutagenesis was used to probe the function of specific Mrs2 domains.
- Permeability assays were conducted using various divalent cations (Ni2+, Ca2+, Mn2+, Co2+).
Main Results:
- Mrs2 forms a high-conductance (155 pS) Mg2+-selective channel.
- Channel open probability is regulated by Mg2+ concentration, decreasing in its presence.
- Mrs2 exhibits lower conductance (45 pS) and permeability to Ni2+, but not Ca2+, Mn2+, or Co2+.
- Mutations disrupt Mg2+ transport or lead to deregulated channel states.
Conclusions:
- Mrs2 functions as a Mg2+-selective channel controlling mitochondrial Mg2+ uptake.
- An intrinsic negative feedback mechanism regulates Mrs2 channel activity based on Mg2+ levels.
- These findings provide critical insights into mitochondrial Mg2+ transport and cellular Mg2+ regulation.
Related Concept Videos
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,...
01:21Structure of Porins
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 precursors...
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...
01:46Electron Transport Chain: Complex I and II
The mitochondrial electron transport chain (ETC) is the main energy generation system in the eukaryotic cells. However, mitochondria also produce cytotoxic reactive oxygen species (ROS) due to the large electron flow during oxidative phosphorylation. While Complex I is one of the primary sources of superoxide radicals, ROS production by Complex II is uncommon and may only be observed in cancer cells with mutated complexes.
ROS generation is regulated and maintained at moderate levels necessary...
ROS generation is regulated and maintained at moderate levels necessary...
01:32Chemiosmosis
Oxidative phosphorylation is a highly efficient process that generates large amounts of adenosine triphosphate (ATP), the basic unit of energy that drives many cellular processes. Oxidative phosphorylation involves two processes— the electron transport chain and chemiosmosis.
Electron Transport Chain
The electron transport chain involves a series of protein complexes on the inner mitochondrial membrane that undergo a series of redox reactions. At the end of this chain, the electrons reduce...
Electron Transport Chain
The electron transport chain involves a series of protein complexes on the inner mitochondrial membrane that undergo a series of redox reactions. At the end of this chain, the electrons reduce...
01:28The 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...