GO:1990229 iron-sulfur cluster assembly complex: Components, Assembly and Research Methods, Genes, Functions and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:1990229 (iron-sulfur cluster assembly complex) is a cellular component defined as a protein complex capable of assembling an iron-sulfur (Fe-S) cluster.
• Fe-S clusters are ancient, ubiquitous cofactors required for electron transfer, catalysis, and regulatory sensing in proteins across all domains of life.
• The core mitochondrial Fe-S assembly complex (also called the ISC assembly complex) includes scaffold proteins such as ISCU, cysteine desulfurase NFS1, and accessory proteins like frataxin (FXN) and ferredoxin-2 (FDX2).
• In plants and algae, Fe-S cluster assembly occurs in mitochondria and plastids, with SufBCD-type complexes operating in some organisms.
• Dysfunction of Fe-S cluster assembly is linked to human diseases including Friedreich ataxia, sideroblastic anemia, and mitochondrial myopathies.
• CRISPR-based knockout, point mutation, and knock-in models are powerful tools to dissect the causal roles of Fe-S assembly genes in health and disease.
Description
Iron-sulfur (Fe-S) clusters are among the most ancient and versatile protein cofactors, essential for electron transfer, enzymatic catalysis, and environmental sensing. The iron-sulfur cluster assembly complex (GO:1990229) is a dedicated cellular machine that builds these clusters and inserts them into recipient apoproteins. This complex is conserved from bacteria to humans, with specialized variants in mitochondria, cytosol, and plastids. Understanding its structure, composition, and regulation is fundamental to cell biology and to deciphering the molecular basis of numerous human disorders. In this article, we provide a research-grade overview of GO:1990229, covering its definition, core components, molecular mechanism, associated genes, disease links, and state-of-the-art methods including CRISPR-based models for functional studies.
iron-sulfur cluster assembly complex At A Glance
| GO ID | GO:1990229 |
|---|---|
| GO term | iron-sulfur cluster assembly complex |
| Ontology | cellular_component |
| Synonym | Fe-S cluster assembly complex, SufBCD complex |
| Major function | Assembly of iron-sulfur (Fe-S) clusters and their insertion into apoproteins |
| Related complexes | Mitochondrial ISC assembly complex, cytosolic CIA machinery, plastid SUF system |
| Key proteins | ISCU, NFS1, FXN, FDX2, ISD11, ACP, and SufBCD components |
| Disease relevance | Friedreich ataxia, sideroblastic anemia, mitochondrial myopathies, cancer |
What Is GO:1990229?
According to the Gene Ontology, GO:1990229 (iron-sulfur cluster assembly complex) is a protein complex capable of assembling an iron-sulfur (Fe-S) cluster. This definition encompasses multi-protein machines that synthesize Fe-S clusters from iron and sulfur donors and transfer them to target proteins. The term is a cellular component and includes complexes such as the SufBCD complex in bacteria and the mitochondrial ISC assembly complex in eukaryotes.
Why Is iron-sulfur cluster assembly complex Important in Cell Biology?
The iron-sulfur cluster assembly complex is essential for life because Fe-S clusters are required for the function of numerous proteins involved in respiration, DNA repair, ribosome biogenesis, and metabolism. Defects in this complex lead to a wide range of human diseases, including neurodegenerative disorders and anemia. Moreover, Fe-S cluster assembly is a target for antimicrobial and anticancer drug development, and its components are being explored as biomarkers and therapeutic targets.
• Fe-S clusters are indispensable cofactors for electron transport chains in mitochondria and chloroplasts.
• The assembly complex is required for the maturation of mitochondrial complex I and other respiratory chain subunits.
• Mutations in Fe-S assembly genes cause Friedreich ataxia, a neurodegenerative disease.
• Defective Fe-S cluster assembly is implicated in sideroblastic anemia and mitochondrial myopathies.
• The complex is involved in iron homeostasis and oxidative stress responses.
• In plants, Fe-S assembly is linked to magnetic field sensing and stress adaptation.
• Algal models reveal evolutionary diversity of Fe-S assembly in plastid-containing organisms.
• CRISPR screens can identify novel regulators of Fe-S cluster assembly and iron metabolism.
Core Biology of GO:1990229
What Happens During iron-sulfur cluster assembly complex?
In simple terms: The complex takes iron and sulfur and builds a tiny iron-sulfur cluster, then hands it off to proteins that need it.
The assembly process begins with the mobilization of sulfur from L-cysteine by a cysteine desulfurase (e.g., NFS1 in eukaryotes), which forms a persulfide intermediate. Iron is delivered by frataxin (FXN) and other chaperones. The scaffold protein ISCU receives the sulfur and iron to assemble a transient Fe-S cluster. Accessory proteins such as ISD11 and ACP stabilize the complex. The cluster is then transferred to recipient apoproteins via dedicated chaperones and carriers.
Structure and Composition of iron-sulfur cluster assembly complex
In simple terms: The complex is made of several proteins that fit together like a molecular factory.
In mitochondria, the core ISC assembly complex consists of NFS1, ISCU, ISD11, ACP, FXN, and FDX2. NFS1 is a pyridoxal phosphate-dependent cysteine desulfurase that provides sulfur. ISCU serves as the scaffold for cluster assembly. FXN is an iron-binding protein that regulates cluster formation. FDX2 is a ferredoxin that supplies electrons for reductive cluster assembly. In bacteria and some plastids, the SufBCD complex forms a similar assembly machine.
Molecular Mechanism of iron-sulfur cluster assembly complex
In simple terms: The complex uses chemical reactions to combine iron and sulfur into a cluster, then passes it to other proteins.
The molecular mechanism involves a series of steps: (1) desulfuration of cysteine by NFS1 to generate a persulfide; (2) transfer of sulfur to ISCU; (3) iron delivery by FXN and possibly other chaperones; (4) reductive coupling to form the Fe-S cluster, with electrons provided by FDX2. The cluster is then transferred to apoproteins via a chaperone/co-chaperone system (e.g., HSC20/HSPA9). Regulation occurs at multiple levels, including iron availability and oxidative stress.
Assembly in Different Cellular Compartments
In simple terms: Different parts of the cell have their own versions of the assembly complex.
In eukaryotes, Fe-S cluster assembly occurs in mitochondria (ISC system), cytosol (CIA system), and in plants also in plastids (SUF system). The mitochondrial ISC complex is the primary source of clusters for mitochondrial proteins and also exports a sulfur-containing compound for cytosolic assembly. The cytosolic CIA machinery matures Fe-S proteins involved in DNA metabolism and translation. In algae with complex plastids, the SUF system operates in the plastid.
Key Genes Involved in GO:1990229 iron-sulfur cluster assembly complex
The following genes encode core components and regulators of the iron-sulfur cluster assembly complex across model organisms.
| Gene | Major Role | Research Relevance |
|---|---|---|
| ISCU | Scaffold protein for Fe-S cluster assembly | Mutations cause myopathy; target for functional studies |
| NFS1 | Cysteine desulfurase; provides sulfur | Essential for cluster assembly; knockout is lethal |
| FXN | Iron chaperone; regulates cluster assembly | Defects cause Friedreich ataxia |
| FDX2 | Ferredoxin; supplies electrons for cluster reduction | Required for Fe-S cluster assembly in mitochondria |
| ISD11 | Stabilizes NFS1 and the core complex | Mutations linked to mitochondrial dysfunction |
| ACP | Acyl carrier protein; structural component | Involved in complex stability |
| HSC20 | Co-chaperone for cluster transfer | Facilitates transfer to apoproteins |
| HSPA9 | Chaperone; assists in cluster transfer | Implicated in neurodegeneration |
| GLRX5 | Glutaredoxin; involved in cluster transfer | Mutations cause sideroblastic anemia |
| SufA | Bacterial scaffold protein | Model for Fe-S assembly |
| SufB | Component of SufBCD complex | Bacterial assembly machine |
| SufC | ATPase component of SufBCD complex | Provides energy for assembly |
| SufD | Component of SufBCD complex | Scaffold in bacteria |
| SufS | Cysteine desulfurase in SUF system | Sulfur donor in bacteria and plastids |
| SufE | Sulfur transfer protein | Essential for SUF function |
| Nfu1 | Cluster transfer protein | Involved in mitochondrial Fe-S protein maturation |
| IBA57 | Cluster transfer protein | Mutations cause multiple mitochondrial dysfunctions syndrome |
How Is iron-sulfur cluster assembly complex Regulated?
The iron-sulfur cluster assembly complex is regulated by iron availability, oxidative stress, and cellular iron-sensing pathways. In eukaryotes, the iron-responsive element/iron regulatory protein (IRE/IRP) system controls the expression of several Fe-S assembly genes, including FXN and ISCU, in response to iron levels. Additionally, the mitochondrial ISC system is regulated by the integrated stress response (ISR) under conditions of mitochondrial dysfunction. In plants, magnetic field exposure has been shown to modulate the expression of Fe-S assembly genes, suggesting environmental regulation.
iron-sulfur cluster assembly complex and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| FXN | Friedreich ataxia | Knockout or knock-in of expanded GAA repeats in iPSCs |
| ISCU | Mitochondrial myopathy | Point mutation knock-in in mouse models |
| GLRX5 | Sideroblastic anemia | CRISPR knockout in erythroid cell lines |
| IBA57 | Multiple mitochondrial dysfunctions syndrome | Knockout in HEK293T cells |
| NFS1 | Cancer cell proliferation | Inducible knockout in cancer cell lines |
Friedreich Ataxia
Friedreich ataxia is caused by reduced expression of frataxin (FXN), a key component of the mitochondrial Fe-S cluster assembly complex. Loss of FXN leads to impaired Fe-S cluster assembly, mitochondrial iron overload, and oxidative stress, resulting in neurodegeneration and cardiomyopathy.
Sideroblastic Anemia and Mitochondrial Myopathies
Mutations in genes encoding Fe-S cluster assembly components, such as GLRX5, ISCU, and IBA57, cause sideroblastic anemia and mitochondrial myopathies. These disorders highlight the critical role of Fe-S cluster assembly in hematopoiesis and muscle function.
Cancer and Metabolic Reprogramming
Altered Fe-S cluster assembly is observed in various cancers, where it supports metabolic reprogramming and redox balance. Targeting the assembly complex is being explored as a therapeutic strategy.
From iron-sulfur cluster assembly complex-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Does loss of ISCU impair Fe-S cluster assembly? | CRISPR knockout of ISCU in HeLa or HEK293T cells |
| Does a specific point mutation in FXN affect cluster assembly? | Knock-in of patient-derived mutation in iPSCs |
| Can overexpression of FDX2 rescue assembly defects? | Overexpression of FDX2 in FXN-knockout cells |
| Where is the complex localized? | Tagged knock-in of ISCU with GFP in mammalian cells |
| What genes regulate Fe-S cluster assembly? | CRISPR library screening in iron-deficient conditions |
| How does SufBCD complex assemble in bacteria? | Knockout of suf genes in E. coli |
How to Study the iron-sulfur cluster assembly complex Process
| Method | What It Measures | Typical Application |
|---|---|---|
| In vitro reconstitution | Fe-S cluster assembly activity | Testing purified components |
| AP-MS | Protein-protein interactions | Identifying complex components |
| RNA-seq | Gene expression changes | Response to iron stress |
| Ribo-seq | Translation efficiency | Regulation of assembly genes |
| CRISPR screen | Gene essentiality and fitness | Identifying novel regulators |
| Fluorescence microscopy | Subcellular localization | Mitochondrial targeting |
| Circular dichroism | Cluster formation | Biophysical characterization |
| Sulfide release assay | Cysteine desulfurase activity | Enzyme kinetics |
Biochemical Assays for Fe-S Cluster Assembly
In vitro reconstitution assays using purified components (e.g., NFS1, ISCU, FXN) can measure cluster assembly by monitoring sulfide release or circular dichroism. These assays are useful for dissecting the molecular mechanism and testing inhibitors.
Proteomics and Interactomics
Affinity purification coupled with mass spectrometry (AP-MS) can identify interacting partners of the assembly complex. Proximity labeling (BioID) can map the interactome in living cells.
Genomic and Transcriptomic Approaches
RNA-seq and ribosome profiling (Ribo-seq) can reveal how Fe-S cluster assembly genes are regulated under iron deficiency or oxidative stress. CRISPR screens can identify novel regulators.
Imaging and Localization
Fluorescence microscopy of tagged components (e.g., ISCU-GFP) allows visualization of mitochondrial localization and dynamics. Electron microscopy can reveal ultrastructural changes in mitochondria upon assembly defects.
How CRISPR Can Be Used to Study GO:1990229 iron-sulfur cluster assembly complex
Knockout
CRISPR knockout of core Fe-S assembly genes (e.g., ISCU, NFS1) in cell lines can abolish cluster assembly, leading to impaired mitochondrial respiration and cell death. These models are valuable for studying the essentiality of the complex and for drug screening.
Point Mutation
Introducing patient-specific point mutations (e.g., in FXN or GLRX5) via CRISPR base editing or homology-directed repair allows precise modeling of disease-associated variants. These models help dissect the functional impact of single amino acid changes on cluster assembly.
Knock-in
Knock-in of tagged versions (e.g., GFP, HA) of assembly components enables live-cell imaging and proteomic studies. Knock-in of disease-relevant mutations (e.g., GAA repeat expansion in FXN) creates isogenic models for drug discovery.
Overexpression
CRISPR activation (CRISPRa) or lentiviral overexpression of Fe-S assembly genes can rescue defects or enhance cluster assembly. Overexpression models are useful for structure-function studies and for testing gain-of-function hypotheses.
How EDITGENE Supports iron-sulfur cluster assembly complex Research
Researchers studying iron-sulfur cluster assembly complex-related genes often need to determine whether a candidate gene is causally involved in Fe-S cluster biogenesis, mitochondrial function, or disease. EDITGENE provides a comprehensive suite of CRISPR-based services to accelerate this research, from gene knockout to precise point mutations and library screening.
Contact EDITGENE today to design your custom CRISPR model for iron-sulfur cluster assembly complex research.
Frequently Asked Questions About iron-sulfur cluster assembly complex
What is GO:1990229?
GO:1990229 is the Gene Ontology term for iron-sulfur cluster assembly complex, a protein complex capable of assembling an iron-sulfur (Fe-S) cluster.
What genes are involved in iron-sulfur cluster assembly complex?
Key genes include ISCU, NFS1, FXN, FDX2, ISD11, ACP, and in bacteria the suf operon genes (sufA, sufB, sufC, sufD, sufS, sufE).
What is the function of the iron-sulfur cluster assembly complex?
It assembles Fe-S clusters from iron and sulfur and inserts them into apoproteins, which are required for electron transfer, catalysis, and regulation.
Where is the iron-sulfur cluster assembly complex located?
In eukaryotes, it is located in mitochondria (ISC system) and cytosol (CIA system); in plants and algae, also in plastids (SUF system).
What diseases are associated with defects in Fe-S cluster assembly?
Friedreich ataxia, sideroblastic anemia, mitochondrial myopathies, and some cancers.
How can I study the iron-sulfur cluster assembly complex using CRISPR?
CRISPR knockout, point mutation knock-in, and overexpression models can be used to dissect gene function and model diseases.
What is the SufBCD complex?
SufBCD is a bacterial iron-sulfur cluster assembly complex, a synonym for GO:1990229, composed of SufB, SufC, and SufD proteins.
What methods are used to measure Fe-S cluster assembly?
In vitro reconstitution, circular dichroism, sulfide release assays, and proteomics are commonly used.
Is the iron-sulfur cluster assembly complex conserved across species?
Yes, it is highly conserved from bacteria to humans, with specialized variants in different cellular compartments.
Can I order custom CRISPR models for Fe-S assembly genes from EDITGENE?
Yes, EDITGENE provides knockout, point mutation, knock-in, and overexpression models for any Fe-S assembly gene, along with screening and bioinformatics services.
Conclusion
The iron-sulfur cluster assembly complex (GO:1990229) is a fundamental cellular machine responsible for the biogenesis of Fe-S clusters, which are essential for numerous biological processes. Its dysfunction is linked to severe human diseases, making it a critical area of research. Advances in CRISPR-based models and high-throughput screening are accelerating our understanding of this complex and opening new avenues for therapeutic intervention. EDITGENE offers comprehensive services to support these research efforts, from custom cell models to bioinformatics analysis.
References
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