Related Experiment Video
Updated: Jul 8, 2026
08:57
Simultaneous Measurement of Superoxide/Hydrogen Peroxide and NADH Production by Flavin-containing Mitochondrial Dehydrogenases
Published on: February 24, 2018
DNA oxidation by charge transport in mitochondria
Edward J Merino1, Jacqueline K Barton
1Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, USA.
Biochemistry
|January 15, 2008
Summary
Researchers used a rhodium probe to detect oxidative DNA damage in mitochondria. This method reveals how DNA damage affects mitochondrial protein packaging and sensing, highlighting cancer-associated mutational hotspots.
Area of Science:
- Mitochondrial biology
- DNA damage and repair
- Biophysical chemistry
Background:
- Mitochondria are crucial for cellular energy and are susceptible to oxidative stress.
- Identifying oxidative DNA damage sites within intact mitochondria is challenging.
- Previous methods relied on external probes, limiting direct observation in functioning mitochondria.
Purpose of the Study:
- To develop a method for directly monitoring oxidative DNA damage in functioning mitochondria.
- To investigate the relationship between DNA damage, protein association, and DNA packaging within mitochondria.
- To identify specific sites of oxidative damage and their potential link to cancer mutations.
Main Methods:
- Utilized a rhodium intercalator, [Rh(phi)2bpy]Cl3, to bind mitochondrial DNA.
- Irradiated mitochondria to induce oxidative DNA damage via the rhodium complex.
- Employed primer extension assays after piperidine treatment to map DNA damage sites.
- Analyzed DNA-mediated charge transport mechanisms for long-range oxidation.
Main Results:
- Successfully monitored oxidative DNA damage directly within functioning mitochondria.
- Identified protein-dependent primer extension stops every ~20 base pairs, indicating dense DNA packaging.
- Pinpointed oxidative damage at specific mitochondrial DNA positions (260 and 298), known cancer mutational hotspots.
- Demonstrated DNA-mediated, long-range oxidative damage via charge transport, even with protein association.
- Observed changes in protein-DNA contacts in response to mitochondrial DNA damage.
Conclusions:
- The rhodium probe method allows direct assessment of oxidative DNA damage in mitochondria.
- Mitochondrial DNA is densely packaged and associated with proteins, influencing damage propagation.
- Specific oxidative lesions in mitochondrial DNA are linked to cancer-associated mutations and alter protein-DNA interactions.
- Mitochondrial DNA damage is sensed by the mitochondrial protein machinery, impacting cellular processes.
Related Concept Videos
01:15Pyruvate Oxidation
After glycolysis, the charged pyruvate molecules enter the mitochondria via active transport and undergo three enzymatic reactions. These reactions ensure that pyruvate can enter the next metabolic pathway so that energy stored in the pyruvate molecules can be harnessed by the cells.
First, the enzyme pyruvate dehydrogenase removes the carboxyl group from pyruvate and releases it as carbon dioxide. The stripped molecule is then oxidized and releases electrons, which are then picked up by NAD+...
First, the enzyme pyruvate dehydrogenase removes the carboxyl group from pyruvate and releases it as carbon dioxide. The stripped molecule is then oxidized and releases electrons, which are then picked up by NAD+...
01:28Electron Transport Chains
The final stage of cellular respiration is oxidative phosphorylation that consists of two steps: the electron transport chain and chemiosmosis. The electron transport chain is a set of proteins found in the inner mitochondrial membrane in eukaryotic cells. Its primary function is to establish a proton gradient that can be used during chemiosmosis to produce ATP and generate electron carriers, such as NAD+ and FAD, that are used in glycolysis and the citric acid cycle.
The ETC is comprised of...
The ETC is comprised of...
01:43Electron Transport Chain: Complex III and IV
During the electron transport chain, electrons from NADH and FADH2 are first transferred to complexes I and II, respectively. These two complexes then transfer the electrons to ubiquinol, which carries them further to complex III. Complex III passes the electrons across the intermembrane space to Cyt c, which carries them further to complex IV. Complex IV donates electrons to oxygen and reduces it to water. As electrons pass through complexes I, III, and IV, the energy released aids the pumping...
01:19Oxidation and Reduction of Organic Molecules
Energy production within a cell involves many coordinated chemical pathways. Most of these pathways are combinations of oxidation and reduction reactions, which occur at the same time. An oxidation reaction strips an electron from an atom in a compound, and the addition of this electron to another compound is a reduction reaction. Because oxidation and reduction usually occur together, these pairs of reactions are called redox reactions.
The removal of an electron from a molecule, results in a...
The removal of an electron from a molecule, results in a...
01:29Role of Reduced Coenzymes NADH and FADH₂
The energy released from the breakdown of the chemical bonds within nutrients can be stored either through the reduction of electron carriers or in the bonds of adenosine triphosphate (ATP). In living systems, a small class of compounds functions as mobile electron carriers, molecules that bind to and shuttle high-energy electrons between compounds in pathways. The principal electron carriers that will be considered originate from the B vitamin group and are derivatives of nucleotides; they are...
01:22Chemiosmosis and ATP Synthesis
The electron transport chain is a critical component of cellular respiration, occurring in the inner mitochondrial membrane. It facilitates the transfer of high-energy electrons from reduced cofactors NADH and FADH₂ to molecular oxygen, the final electron acceptor. This transfer of electrons through a series of protein complexes is tightly coupled to the translocation of protons across the membrane, generating a proton gradient essential for ATP synthesis.Electron Flow and Proton...