Related Experiment Video
Updated: Jun 30, 2026
05:27
Inner Mitochondrial Membrane Sensitivity to Na+ Reveals Partially Segmented Functional CoQ Pools
Published on: July 20, 2022
Nitrite reductase activity of cytochrome c
Swati Basu1, Natalia A Azarova, Michael D Font
1Department of Physics, Wake Forest University, Winston-Salem, North Carolina 27109, USA.
The Journal of Biological Chemistry
|September 30, 2008
Summary
Nitrite, once thought inert, is a key signaling molecule. Researchers discovered that cytochrome c, a mitochondrial protein, can reduce nitrite to nitric oxide (NO), impacting cellular respiration and signaling.
Area of Science:
- Biochemistry
- Cellular Biology
- Physiology
Background:
- Nitrite (NO2-) is increasingly recognized as a vital signaling molecule, mediating responses like hypoxic vasodilation and cytoprotection.
- Previously considered biologically inert, nitrite is now understood to be a crucial regulator of gene and protein expression.
- Nitrite's signaling function is primarily through its reduction to nitric oxide (NO) by heme-containing proteins.
Purpose of the Study:
- To investigate the potential of mitochondrial proteins to reduce nitrite to nitric oxide (NO).
- To identify novel nitrite reductase activities within cellular respiration pathways.
- To explore the physiological implications of nitrite reduction by mitochondrial components.
Main Methods:
- Investigated the interaction between nitrite and purified cytochrome c under varying conditions.
- Utilized spectroscopic methods to detect NO production.
- Assessed the impact of NO generated by cytochrome c on mitochondrial respiration.
Main Results:
- Demonstrated that cytochrome c effectively reduces nitrite to NO under anoxic and acidic conditions.
- Showed that this nitrite reductase activity is dependent on the pentacoordination of heme iron in cytochrome c.
- Confirmed that NO generated by pentacoordinate cytochrome c inhibits mitochondrial respiration.
Conclusions:
- Cytochrome c possesses a novel nitrite reductase activity, contributing to cellular NO signaling.
- This function is regulated by specific heme iron coordination and cellular conditions (anoxia, acidity).
- The findings suggest a new role for cytochrome c in regulating mitochondrial function and cellular signaling pathways, including hypoxic, redox, and apoptotic signaling.
More Related Videos
08:03Unveiling Xenobiotic Transport and Effects in Isolated Mitochondria: Insights from Respirometric and Enzymatic Assays
Published on: March 7, 2025
08:25Measuring Nitrite and Nitrate, Metabolites in the Nitric Oxide Pathway, in Biological Materials using the Chemiluminescence Method
Published on: December 25, 2016
Related Concept Videos
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...
01:46Electron 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...
01:27Redox Reactions
Redox reactions are vital biochemical processes that underpin energy metabolism in cells. These reactions involve the transfer of electrons between molecules, occurring in tandem as oxidation and reduction. Oxidation refers to the loss of electrons, while reduction denotes their gain. This coupling ensures the seamless flow of electrons through metabolic pathways. For example, in bacterial metabolism, glucose undergoes oxidation to carbon dioxide, while oxygen is simultaneously reduced to...
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...
01:22Inorganic Nitrogen Assimilation
Nitrogen is an essential element in biological systems, forming a crucial component of proteins, nucleic acids, and other cellular constituents. Many bacteria and archaea acquire nitrogen in the form of nitrate (NO₃⁻) or ammonia (NH₃), which are then assimilated into biomolecules through specific enzymatic pathways.Assimilatory Nitrate ReductionWhen nitrate enters the cell, it undergoes a two-step reduction process known as assimilatory nitrate reduction. Initially, the enzyme nitrate reductase...
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...