GO:0031071 cysteine desulfurase activity: Mechanism, Genes and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0031071 cysteine desulfurase activity catalyzes the reaction L-cysteine + [enzyme]-cysteine = L-alanine + [enzyme]-S-sulfanylcysteine, mobilizing sulfur from free cysteine for iron-sulfur cluster and thio-modification biosynthesis.
• The reaction proceeds through a pyridoxal 5'-phosphate (PLP)-dependent persulfide intermediate on a conserved catalytic cysteine, which is then transferred to scaffold proteins or sulfur acceptors.
• Human NFS1 is the principal cysteine desulfurase in mitochondria, supplying sulfur for ISC-mediated iron-sulfur cluster assembly; its activity is regulated by accessory proteins such as CyaY/frataxin and TusA.
• Bacterial and cyanobacterial homologs (IscS, SufS, NifS) define the mechanistic paradigm and are validated by direct enzymatic assays and structural studies.
• NFS1 is implicated in colorectal cancer chemosensitivity, liver cancer metastasis, and ferroptosis resistance, making it a candidate therapeutic target.
• CRISPR knockout, point-mutation, knock-in, and overexpression models enable causal dissection of cysteine desulfurase function in disease and metabolism.
Description
Cysteine desulfurase activity (GO:0031071) is a molecular function that liberates sulfur from L-cysteine and transfers it to a conserved cysteine residue on the enzyme itself, forming an enzyme-bound persulfide. This activity is the entry point for sulfur mobilization in the biosynthesis of iron-sulfur (Fe-S) clusters, thiamine, molybdopterin, and thio-modified tRNAs, and it is therefore essential for mitochondrial and cytosolic iron homeostasis. The reaction is pyridoxal 5'-phosphate (PLP)-dependent and proceeds via a covalent enzyme-substrate intermediate, making it mechanistically distinct from simple cysteine catabolism. In humans, the principal cysteine desulfurase is NFS1, which partners with ISCU, frataxin (FXN), and other ISC assembly factors to deliver sulfur to Fe-S cluster scaffolds. Loss of NFS1 function impairs Fe-S cluster biogenesis, activates the iron starvation response, and can trigger ferroptosis, a form of iron-dependent cell death. In cancer, NFS1 activity supports proliferation and stress resistance; its inhibition or phosphorylation status alters sensitivity to oxaliplatin and other therapies. Because cysteine desulfurase activity sits at the intersection of amino acid metabolism, iron-sulfur cluster assembly, and redox biology, it is a high-value target for mechanistic, structural, and translational research. This article summarizes the definition, mechanism, key genes, disease links, and experimental methods for studying GO:0031071, with a focus on CRISPR-based models and functional assays.
cysteine desulfurase activity At A Glance
| GO ID | GO:0031071 |
|---|---|
| GO term | cysteine desulfurase activity |
| Ontology | molecular_function |
| Synonym | cysteine desulfurylase activity; IscS; L-cysteine:enzyme cysteine sulfurtransferase activity; NIFS; SufS |
| Definition | Catalysis of the reaction: L-cysteine + [enzyme]-cysteine = L-alanine + [enzyme]-S-sulfanylcysteine. |
| Major function | Mobilizes sulfur from L-cysteine for iron-sulfur cluster assembly, thio-modification of tRNA, and related biosynthetic pathways. |
| Cofactor | Pyridoxal 5'-phosphate (PLP) |
| Catalytic intermediate | Enzyme-bound persulfide (S-sulfanylcysteine) |
| Representative enzymes | NFS1 (human), IscS (bacteria), SufS (bacteria), NifS (bacteria), cyanobacterial cysteine desulfurases |
What Is GO:0031071?
GO:0031071 cysteine desulfurase activity is defined as catalysis of the reaction: L-cysteine + [enzyme]-cysteine = L-alanine + [enzyme]-S-sulfanylcysteine. In other words, the enzyme uses pyridoxal 5'-phosphate (PLP) to abstract sulfur from free L-cysteine, generating L-alanine and a covalent persulfide (S-sulfanylcysteine) on its own catalytic cysteine residue. This enzyme-bound persulfide is the activated sulfur donor for downstream Fe-S cluster assembly and other sulfur-transfer reactions.
Why Is cysteine desulfurase activity Important in Cell Biology?
Cysteine desulfurase activity is essential because it provides the sulfur used to build iron-sulfur clusters, which are cofactors for numerous enzymes in respiration, DNA repair, and metabolism. In humans, NFS1 dysfunction impairs mitochondrial Fe-S cluster assembly and has been linked to cancer chemoresistance, ferroptosis regulation, and metastatic progression. The activity is also a validated target in bacteria and parasites, where IscS/SufS homologs are required for survival and virulence. Understanding its mechanism and regulation is therefore central to both fundamental cell biology and therapeutic development.
• Supplies sulfur for iron-sulfur cluster biogenesis, a pathway required for mitochondrial respiration and genome maintenance.
• Regulates ferroptosis sensitivity, a key determinant of cancer cell death and therapy response.
• Modulates oxaliplatin chemosensitivity in colorectal cancer through NFS1 phosphorylation and PANoptosis.
• Promotes liver cancer metastasis and ferroptosis resistance after microwave ablation via NFS1-dependent mechanisms.
• Is a target of eprenetapopt, which inhibits NFS1 and synergizes with serine/glycine restriction.
• Bacterial IscS/SufS homologs are essential for Fe-S cluster assembly and are studied as antibacterial targets.
• Cyanobacterial cysteine desulfurases display unusual antioxidant activity, linking sulfur mobilization to oxidative stress defense.
• Mutations in FDX2, a mitochondrial ferredoxin, can suppress frataxin deficiency by modulating Fe-S cluster assembly, highlighting pathway plasticity.
• Direct NMR-based activity assays enable precise measurement of human NFS1 catalysis and structural element contributions.
• CyaY and TusA regulate ISC- and SUF-mediated cysteine desulfurase activity, revealing multilayered control.
What Happens During cysteine desulfurase activity?
Substrate binding and PLP activation
In simple terms: The enzyme grabs cysteine and activates it using a vitamin B6-derived cofactor.
Cysteine desulfurases are pyridoxal 5'-phosphate (PLP)-dependent enzymes. The PLP cofactor forms an internal aldimine with the catalytic lysine, which is displaced by the incoming L-cysteine to form an external aldimine. This activates the cysteine for subsequent bond cleavage. Structural and mechanistic studies of bacterial and human enzymes have defined the key residues that position the substrate and stabilize the PLP intermediate.
Persulfide formation on the catalytic cysteine
In simple terms: The enzyme pulls sulfur off cysteine and holds it on its own surface.
Following PLP-mediated activation, the sulfur atom of L-cysteine is transferred to a conserved cysteine residue on the enzyme, forming an enzyme-bound persulfide (S-sulfanylcysteine) and releasing L-alanine. This covalent intermediate is the hallmark of cysteine desulfurase activity and is directly detectable by mass spectrometry and NMR. The reaction is reversible in vitro, but in cells the persulfide is rapidly consumed by downstream sulfur acceptors.
Sulfur transfer to scaffold proteins
In simple terms: The held sulfur is handed off to a scaffold that builds iron-sulfur clusters.
The persulfide sulfur is transferred to scaffold proteins such as ISCU in the ISC pathway or SufU/SufB in the SUF pathway, where it is used to assemble iron-sulfur clusters. In bacteria, IscS interacts with IscU, while SufS partners with SufE and SufB; these protein-protein interactions are regulated by accessory factors like CyaY and TusA. In humans, NFS1 transfers sulfur to ISCU in a process facilitated by frataxin (FXN) and the ferredoxin FDX2.
Regulation by accessory proteins and post-translational modifications
In simple terms: Helper proteins and chemical tags control how fast the enzyme works.
Cysteine desulfurase activity is not constitutive; it is modulated by protein partners and post-translational modifications. CyaY (frataxin homolog) and TusA regulate ISC- and SUF-mediated activity in bacteria, affecting sulfur flux. In human cells, NFS1 phosphorylation weakens oxaliplatin-based chemosensitivity by preventing PANoptosis, indicating that phosphorylation status directly impacts pathway output. Additionally, histone lactylation drives liver cancer metastasis by facilitating NFS1-mediated ferroptosis resistance, linking metabolic state to desulfurase function.
Integration with iron-sulfur cluster assembly and ferroptosis
In simple terms: The sulfur from this enzyme feeds into iron-sulfur clusters and affects cell death.
The sulfur mobilized by cysteine desulfurases is essential for Fe-S cluster assembly, which in turn supports enzymes involved in redox homeostasis and lipid repair. When NFS1 activity is inhibited, Fe-S cluster assembly fails, iron starvation response is activated, and ferroptosis can be triggered. Eprenetapopt inhibits NFS1 and synergizes with serine/glycine dietary restriction to induce ferroptosis in cancer cells. This connects cysteine desulfurase activity directly to cell death pathways and metabolic stress responses.
Key Genes Involved in GO:0031071 cysteine desulfurase activity
The following genes and proteins are directly associated with cysteine desulfurase activity (GO:0031071) or its regulation, based on published biochemical and genetic studies.
| Gene | Major Role | Research Relevance |
|---|---|---|
| NFS1 | Human mitochondrial cysteine desulfurase; primary sulfur donor for Fe-S cluster assembly | Cancer chemosensitivity, ferroptosis, liver metastasis |
| IscS | Bacterial cysteine desulfurase in the ISC pathway | Model enzyme for mechanism and Fe-S cluster biogenesis |
| SufS | Bacterial cysteine desulfurase in the SUF pathway | Alternative sulfur mobilization under oxidative stress |
| NifS | Bacterial cysteine desulfurase involved in nitrogenase metallocluster biosynthesis | First identified cysteine desulfurase; foundational for the field |
| ISCU | Fe-S cluster scaffold protein that receives sulfur from NFS1/IscS | Essential for Fe-S cluster assembly and mitochondrial function |
| FXN | Frataxin; regulates NFS1 activity and Fe-S cluster assembly | Friedreich ataxia and mitochondrial iron homeostasis |
| FDX2 | Mitochondrial ferredoxin; provides electrons for Fe-S cluster assembly | Mutations suppress frataxin deficiency |
| CyaY | Bacterial frataxin homolog; regulates cysteine desulfurase activity | Modulates ISC- and SUF-mediated sulfur transfer |
| TusA | Sulfur transfer protein; regulates cysteine desulfurase activity | Affects ISC- and SUF-mediated pathways |
| SUFE | Sulfur acceptor in the SUF pathway | Partners with SufS for sulfur transfer |
| SufU | Scaffold in the SUF pathway | Receives sulfur from SufS |
| SufB | Component of the SUF Fe-S cluster assembly complex | Downstream of SufS |
| PLP | Pyridoxal 5'-phosphate cofactor | Essential for catalytic activity |
| ISD11 | Accessory protein for NFS1 in eukaryotes | Required for NFS1 stability and function |
| ACO1 | Aconitase; Fe-S cluster enzyme downstream of NFS1 | Readout of Fe-S cluster status |
| GPX4 | Glutathione peroxidase 4; ferroptosis regulator | Linked to NFS1 inhibition and ferroptosis |
| SLC7A11 | Cystine/glutamate antiporter; affects cysteine availability | Modulates cysteine desulfurase substrate supply |
How Is cysteine desulfurase activity Regulated?
Cysteine desulfurase activity is regulated at multiple levels. In bacteria, accessory proteins CyaY and TusA directly modulate ISC- and SUF-mediated activity, affecting sulfur flux to Fe-S cluster scaffolds. In human cells, NFS1 is phosphorylated, and this modification weakens oxaliplatin-based chemosensitivity by preventing PANoptosis, indicating that kinase/phosphatase signaling controls desulfurase output. Histone lactylation promotes NFS1-mediated ferroptosis resistance in liver cancer after microwave ablation, linking metabolic state to desulfurase regulation. Additionally, substrate availability (L-cysteine) and iron status influence pathway activity, as shown by the iron starvation response triggered upon NFS1 inhibition.
cysteine desulfurase activity and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| NFS1 | Colorectal cancer chemosensitivity; liver cancer metastasis; ferroptosis | NFS1 knockout or point-mutation cancer cell lines; xenograft models |
| FXN | Friedreich ataxia; mitochondrial iron homeostasis | FXN knockout or knock-in models; FDX2 suppressor mutations |
| FDX2 | Mitochondrial Fe-S cluster assembly; frataxin deficiency suppression | FDX2 point-mutation knock-in cells |
| ISCU | Fe-S cluster assembly defects; mitochondrial myopathy | ISCU knockout or overexpression cell models |
| SLC7A11 | Ferroptosis regulation; cysteine availability | SLC7A11 knockout or overexpression cells |
Cancer chemosensitivity and metastasis
NFS1 phosphorylation weakens oxaliplatin-based chemosensitivity in colorectal cancer by preventing PANoptosis, suggesting that cysteine desulfurase activity modulates therapy response. In liver cancer, histone lactylation drives metastasis by facilitating NFS1-mediated ferroptosis resistance after microwave ablation, linking desulfurase function to metastatic progression. Inhibition of NFS1 by eprenetapopt triggers ferroptosis and synergizes with serine/glycine dietary restriction, highlighting a therapeutic strategy.
Ferroptosis and metabolic stress
Cysteine desulfurase activity is required for Fe-S cluster assembly; its inhibition causes iron starvation and ferroptosis in cancer cells. This connects GO:0031071 to redox biology and cell death pathways, with implications for cancers dependent on NFS1 for survival.
Mitochondrial and neurodegenerative disease
Mutations in FDX2, a mitochondrial ferredoxin involved in Fe-S cluster assembly, suppress frataxin deficiency, indicating that cysteine desulfurase pathway components can compensate for defects in Friedreich ataxia models. This suggests that modulating cysteine desulfurase activity may have therapeutic potential in mitochondrial disorders.
From cysteine desulfurase activity-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Does NFS1 loss impair Fe-S cluster assembly and trigger ferroptosis? | NFS1 knockout cell lines (CRISPR) |
| Does NFS1 phosphorylation affect oxaliplatin sensitivity? | NFS1 point-mutation knock-in (phospho-mutant) |
| Does NFS1 overexpression promote metastasis? | NFS1 overexpression in liver cancer cells |
| How do FDX2 mutations suppress frataxin deficiency? | FDX2 point-mutation knock-in in FXN-deficient cells |
| What is the role of CyaY/TusA in regulating desulfurase activity? | Bacterial knockout or overexpression strains |
| Can tagged NFS1 be used to study protein interactions? | Tagged knock-in (e.g., FLAG-HA) NFS1 cells |
How to Study the cysteine desulfurase activity Process
| Method | What It Measures | Typical Application |
|---|---|---|
| NMR-based activity assay | Direct cysteine desulfurase catalysis and persulfide formation | Human NFS1 mechanistic studies |
| Radioactive sulfur transfer assay | Sulfur mobilization from cysteine to acceptors | Bacterial IscS/SufS activity |
| CRISPR knockout | Loss-of-function effects on Fe-S cluster assembly and ferroptosis | Cancer cell lines |
| Phospho-mutant knock-in | Effect of NFS1 phosphorylation on drug sensitivity | Colorectal cancer models |
| Overexpression | Gain-of-function in metastasis and ferroptosis resistance | Liver cancer cells |
| Affinity purification-MS | Protein-protein interactions of NFS1 complex | Endogenous tagged knock-in cells |
| Aconitase activity assay | Fe-S cluster status | Readout of NFS1 inhibition |
| Lipid peroxidation assay | Ferroptosis induction | Cancer cells treated with NFS1 inhibitors |
Direct enzymatic assays for cysteine desulfurase activity
Cysteine desulfurase activity can be measured directly by monitoring L-alanine production or persulfide formation. NMR-based assays have been developed to determine human NFS1 activity and to study the functional role of key structural elements. Bacterial enzymes are often assayed spectrophotometrically or by radioactive sulfur transfer.
Genetic and CRISPR screens
CRISPR knockout screens can identify genes that modulate sensitivity to NFS1 inhibition or ferroptosis inducers. Point-mutation knock-in of phosphorylation sites in NFS1 allows dissection of post-translational regulation. Overexpression models help test gain-of-function effects in metastasis and therapy resistance.
Proteomics and interaction studies
Affinity purification coupled to mass spectrometry can identify NFS1 interaction partners such as ISCU, ISD11, and FXN. Tagged knock-in cell lines enable endogenous complex isolation. These methods reveal how accessory proteins regulate cysteine desulfurase activity.
Metabolic and redox profiling
Fe-S cluster status can be assessed by measuring aconitase activity or iron starvation response markers. Ferroptosis is monitored by lipid peroxidation assays and GPX4 levels. These readouts connect cysteine desulfurase activity to cellular metabolism and death pathways.
How CRISPR Can Be Used to Study GO:0031071 cysteine desulfurase activity
Knockout
CRISPR knockout of NFS1 or its bacterial homologs (IscS, SufS) abolishes cysteine desulfurase activity, impairing Fe-S cluster assembly and triggering iron starvation responses. NFS1 knockout cancer cell lines are used to test ferroptosis sensitivity and drug synergy. Bacterial knockout strains define essentiality and pathway redundancy.
Point Mutation
Point-mutation knock-in of NFS1 phosphorylation sites (e.g., phospho-deficient or phospho-mimetic) can dissect how post-translational modifications affect oxaliplatin sensitivity and PANoptosis. Mutating the catalytic cysteine or PLP-binding lysine abolishes activity and serves as a negative control.
Knock-in
Tagged knock-in of NFS1 (e.g., FLAG, HA, or GFP) enables endogenous complex purification and live-cell imaging. Knock-in of disease-associated FDX2 mutations can model frataxin deficiency suppression. These models preserve native regulation and are ideal for mechanistic studies.
Overexpression
Overexpression of NFS1 or bacterial cysteine desulfurases increases sulfur flux and can promote ferroptosis resistance and metastasis in cancer models. Overexpression in bacteria is used to produce recombinant enzyme for structural and kinetic studies.
How EDITGENE Supports cysteine desulfurase activity Research
Researchers studying cysteine desulfurase activity-related genes often need to determine whether a candidate gene is causally involved in Fe-S cluster assembly, ferroptosis, or cancer phenotypes. EDITGENE provides CRISPR-based cell model services to enable precise genetic dissection of GO:0031071 and its regulatory network.
Contact EDITGENE today to design your custom CRISPR model for cysteine desulfurase activity research.
Frequently Asked Questions About cysteine desulfurase activity
What is cysteine desulfurase activity?
Cysteine desulfurase activity (GO:0031071) is a molecular function that catalyzes the reaction L-cysteine + [enzyme]-cysteine = L-alanine + [enzyme]-S-sulfanylcysteine, mobilizing sulfur from cysteine for Fe-S cluster assembly and related pathways.
What genes are involved in cysteine desulfurase activity?
Key genes include NFS1 in humans, and IscS, SufS, and NifS in bacteria; accessory proteins such as ISCU, FXN, FDX2, CyaY, and TusA regulate the activity.
What is the GO ID for cysteine desulfurase activity?
The Gene Ontology ID is GO:0031071, under the molecular_function aspect.
How is cysteine desulfurase activity measured?
It can be measured by NMR-based assays, radioactive sulfur transfer, or by monitoring L-alanine production and persulfide formation.
What is the role of NFS1 in cancer?
NFS1 supports Fe-S cluster assembly and ferroptosis resistance; its phosphorylation weakens oxaliplatin sensitivity, and its inhibition triggers ferroptosis in cancer cells.
What diseases are linked to cysteine desulfurase activity?
It is linked to colorectal cancer chemosensitivity, liver cancer metastasis, ferroptosis-related cell death, and mitochondrial disorders such as Friedreich ataxia through FDX2 and FXN.
What is the catalytic mechanism of cysteine desulfurase?
It uses pyridoxal 5'-phosphate (PLP) to form an external aldimine with L-cysteine, then transfers sulfur to a catalytic cysteine to form a persulfide, releasing L-alanine.
How do CyaY and TusA regulate cysteine desulfurase activity?
CyaY and TusA modulate ISC- and SUF-mediated cysteine desulfurase activity, affecting sulfur flux to Fe-S cluster scaffolds.
Can CRISPR be used to study cysteine desulfurase activity?
Yes, CRISPR knockout, point-mutation knock-in, tagged knock-in, and overexpression models enable causal studies of NFS1 and related genes in disease and metabolism.
What is the connection between cysteine desulfurase and ferroptosis?
Inhibition of NFS1 impairs Fe-S cluster assembly, activates iron starvation, and triggers ferroptosis; eprenetapopt inhibits NFS1 and synergizes with serine/glycine restriction.
Conclusion
Cysteine desulfurase activity (GO:0031071) is a central molecular function that mobilizes sulfur from L-cysteine for Fe-S cluster assembly and related biosynthetic pathways. Its human representative NFS1 is implicated in cancer chemosensitivity, metastasis, and ferroptosis, while bacterial homologs provide mechanistic paradigms. Understanding its regulation by accessory proteins and post-translational modifications is key to therapeutic development. CRISPR-based cell models and direct enzymatic assays are essential tools for dissecting this pathway and translating findings into disease interventions.
References
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- 2. Huang J et al.. 2025. Histone lactylation drives liver cancer metastasis by facilitating NSF1-mediated ferroptosis resistance after microwave ablation.. Redox Biol 81:103553 PMID: 39970777
- 3. Olivieri P et al.. 2024. CyaY and TusA regulate ISC- and SUF-mediated l-cysteine desulfurase activity.. RSC Chem Biol 5(11):1165-1176 PMID: 39372677
- 4. Sewell KE et al.. 2023. Direct Cysteine Desulfurase Activity Determination by NMR and the Study of the Functional Role of Key Structural Elements of Human NFS1.. ACS Chem Biol 18(7):1534-1547 PMID: 37410592
- 5. Fujihara KM et al.. 2022. Eprenetapopt triggers ferroptosis, inhibits NFS1 cysteine desulfurase, and synergizes with serine and glycine dietary restriction.. Sci Adv 8(37):eabm9427 PMID: 36103522
- 6. Meisel JD et al.. 2026. Mutations in mitochondrial ferredoxin FDX2 suppress frataxin deficiency.. Nature 649(8097):713-720 PMID: 41372402
- 7. Zheng L et al.. 1993. Cysteine desulfurase activity indicates a role for NIFS in metallocluster biosynthesis.. Proc Natl Acad Sci U S A 90(7):2754-8 PMID: 8464885
- 8. Banerjee M et al.. 2017. Molecular basis of function and the unusual antioxidant activity of a cyanobacterial cysteine desulfurase.. Biochem J 474(14):2435-2447 PMID: 28592683
