GO:0047726 iron-cytochrome-c reductase activity

Iron-cytochrome-c reductase activity (GO:0047726) is a molecular function that catalyzes the reversible redox reaction between ferric iron (Fe3+) and ferrous cytochrome c (Fe(II)-[cytochrome c]), yielding ferrous iron (Fe2+) and ferric cytochrome c (Fe(III)-[cytochrome c]). This activity sits at the intersection of iron metabolism and mitochondrial electron transport, influencing both cellular iron homeostasis and the redox state of cytochrome c. Because iron is essential for numerous biological processes, including oxygen transport, DNA synthesis, and oxidative phosphorylation, the enzyme responsible for this interconversion is of broad physiological relevance. In iron-deficiency states, tissue cytochrome c levels and iron-dependent enzyme activities are altered, underscoring the importance of iron-cytochrome-c reductase activity in maintaining normal cellular function. In acidophilic bacteria, a homologous activity participates in iron oxidation and energy generation, and its inhibition by tungsten disrupts growth, demonstrating its role in microbial bioenergetics. Researchers studying iron metabolism, mitochondrial function, and redox signaling therefore require reliable tools to manipulate and measure this activity in model systems [1,2].

According to the Gene Ontology, iron-cytochrome-c reductase activity (GO:0047726) is defined as the catalysis of the reaction: Fe3+ + Fe(II)-[cytochrome c] = Fe2+ + Fe(III)-[cytochrome c]. In other words, it is an oxidoreductase that transfers an electron from ferrous cytochrome c to ferric iron, or vice versa, thereby interconverting the oxidation states of iron and cytochrome c. This activity is synonymous with ferrocytochrome-c:Fe3+ oxidoreductase activity and iron-cytochrome c reductase activity.

Iron-cytochrome-c reductase activity is important because it directly links iron redox chemistry to cytochrome c, a key electron carrier in mitochondrial respiration and apoptosis. By interconverting Fe3+ and Fe2+, this activity helps regulate the labile iron pool, which influences oxidative stress through Fenton chemistry. In iron deficiency, changes in tissue cytochrome c and iron-dependent enzymes can impair energy metabolism and cellular function. In bacteria, the corresponding activity supports iron oxidation and growth, and its inhibition by tungsten disrupts cellular energetics. Thus, understanding this activity is relevant to iron biology, mitochondrial physiology, and microbial bioenergetics.

The following genes and proteins are associated with iron-cytochrome-c reductase activity or related iron-cytochrome redox processes, based on published literature.

Iron-cytochrome-c reductase activity is regulated at multiple levels. Cellular iron status directly influences the expression of iron metabolism genes through the IRP/IRE system, affecting the availability of substrates and cofactors. In iron deficiency, tissue cytochrome c levels and iron-dependent enzyme activities are reduced, indicating that iron availability modulates this activity. In bacteria, tungsten competes with molybdenum or iron in metalloenzymes, inhibiting iron-cytochrome-c reductase activity and growth. Additionally, redox balance and oxidative stress can post-translationally modify the enzyme or its substrates, altering activity.

Iron deficiency leads to decreased cytochrome c levels and altered iron-dependent enzyme activities in tissues, which can impair mitochondrial respiration and energy production. This highlights the importance of iron-cytochrome-c reductase activity in maintaining normal cellular function under iron-limited conditions.

Dysregulation of iron-cytochrome-c reductase activity may contribute to oxidative stress by increasing labile iron, which can promote Fenton chemistry and lipid peroxidation. Such mechanisms are implicated in neurodegenerative diseases where iron accumulation and mitochondrial dysfunction are observed.

Altered iron metabolism and redox balance are hallmarks of cancer cells. Changes in iron-cytochrome-c reductase activity could affect cytochrome c-mediated apoptosis and cellular redox status, influencing tumor growth and survival.

In Acidithiobacillus ferrooxidans, inhibition of iron-cytochrome-c reductase activity by tungsten disrupts iron oxidation and energy generation, affecting bacterial growth. This has implications for bioleaching and microbial pathogenesis.

Direct measurement of iron-cytochrome-c reductase activity can be performed using spectrophotometric assays that monitor the reduction of Fe3+ or the oxidation of ferrous cytochrome c. These assays are essential for validating CRISPR models and for kinetic studies.

Genome-wide CRISPR knockout or activation screens can identify genes that regulate iron-cytochrome-c reductase activity or are synthetic lethal with its loss. Such screens are powerful for uncovering novel components of iron metabolism.

Affinity purification coupled with mass spectrometry can identify protein interaction partners of the enzyme, revealing regulatory complexes and substrates. This approach helps place the activity within cellular networks.

Genetically encoded redox sensors and iron-sensitive fluorescent probes can monitor real-time changes in iron and cytochrome c redox states in live cells. These methods provide spatial and temporal resolution of the activity.

Researchers studying iron-cytochrome-c reductase activity-related genes often need to determine whether a candidate gene is causally involved in iron metabolism, mitochondrial function, or disease. EDITGENE provides a comprehensive suite of CRISPR-based services to generate precisely engineered cell models, enabling rigorous functional validation and mechanistic studies.

Iron-cytochrome-c reductase activity (GO:0047726) is a fundamental molecular function that bridges iron redox chemistry and cytochrome c biology, with critical roles in cellular iron homeostasis, mitochondrial function, and microbial energy metabolism [1,2]. Dysregulation of this activity is implicated in iron deficiency, oxidative stress, and various diseases, making it an important target for research. Advances in CRISPR-based gene editing and functional genomics provide unprecedented opportunities to dissect the genes and pathways controlling this activity, paving the way for new therapeutic strategies [1,2].