GO:0140439 protein-cysteine S-stearoyltransferase activity: Mechanism, Genes and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0140439 describes the enzymatic transfer of a stearoyl (octadecanoyl) group from octadecanoyl-CoA to a cysteine sulfur on a protein, forming an S-octadecanoyl-L-cysteinyl protein.
• This activity belongs to the broader family of protein lipidation reactions, which include S-palmitoylation and other S-acylation events that control protein membrane targeting and signaling.
• Cysteine thiol chemistry is central to redox signaling, and S-acylation competes with oxidation, S-nitrosylation, persulfidation and S-guanylation at the same cysteine residues [1,4,5,6,8].
• The reaction is mechanistically related to other acyltransferase activities that use acyl-CoA donors and a catalytic cysteine or histidine in a conserved domain.
• Dysregulated protein lipidation, including S-stearoylation, is linked to cancer, neurodegeneration and immune dysfunction, making the enzyme a candidate drug target.
• CRISPR knockout, point-mutation, knock-in and overexpression models are essential to test whether a candidate S-stearoyltransferase is causally involved in a phenotype.
Description
Protein-cysteine S-stearoyltransferase activity (GO:0140439) is a molecular function that catalyzes the transfer of a stearoyl group, systematically named octadecanoyl, to the sulfur atom of a cysteine residue within a protein molecule. The reaction consumes octadecanoyl-CoA and releases coenzyme A, generating an S-octadecanoyl-L-cysteinyl protein. This covalent modification is a type of protein lipidation, a broad class of post-translational modifications that anchor proteins to membranes and modulate protein-protein interactions. Because cysteine thiols are also targets of oxidation, S-nitrosylation, persulfidation and S-guanylation, S-stearoylation must be understood within the wider context of cysteine redox and electrophile signaling [1,4,5,6,8]. Researchers study GO:0140439 to understand how cells control protein localization, signaling output and metabolic adaptation, and to identify therapeutic opportunities in diseases where lipid modification is perturbed.
protein-cysteine S-stearoyltransferase activity At A Glance
| GO ID | GO:0140439 |
|---|---|
| GO term | protein-cysteine S-stearoyltransferase activity |
| Ontology | molecular_function |
| Synonym | none listed in QuickGO |
| Major function | Transfer of a stearoyl (octadecanoyl) group from octadecanoyl-CoA to a cysteine sulfur on a protein, releasing CoA |
| Reaction | octadecanoyl-CoA + L-cysteinyl-[protein] = CoA + S-octadecanoyl-L-cysteinyl-[protein] |
| Substrate | octadecanoyl-CoA (stearoyl-CoA) and a protein cysteine thiol |
| Product | S-octadecanoyl-L-cysteinyl-[protein] and coenzyme A |
| Related activity | protein-cysteine S-palmitoyltransferase activity and other S-acyltransferases |
What Is GO:0140439?
In simple terms, GO:0140439 is the enzyme activity that attaches a long fatty acid called stearate to a cysteine amino acid on a target protein. The official definition states: Catalysis of the transfer of a stearoyl (systematic name, octadecanoyl) group to a sulfur atom on the cysteine of a protein molecule, in the reaction: octadecanoyl-CoA + L-cysteinyl-[protein] = CoA + S-octadecanoyl-L-cysteinyl-[protein]. This activity is a molecular function and is distinct from S-palmitoylation, although both belong to the S-acyltransferase family and share mechanistic features.
Why Is protein-cysteine S-stearoyltransferase activity Important in Cell Biology?
GO:0140439 matters because S-stearoylation is a covalent lipid modification that can change a protein's hydrophobicity, membrane affinity and interaction partners, thereby influencing signaling, trafficking and metabolism. Because cysteine is a redox-sensitive residue, S-stearoylation is also part of a competitive landscape that includes S-nitrosylation, persulfidation and S-guanylation, so understanding this activity helps explain how cells integrate lipid and redox signals [1,4,5,6,8]. In disease, altered protein lipidation has been associated with cancer, neurodegeneration and immune disorders, making the enzymes that carry out GO:0140439 attractive targets for mechanistic and therapeutic studies.
• Controls membrane targeting and subcellular localization of substrate proteins through covalent lipid attachment.
• Modulates protein-protein interactions and signaling output in immune cells and other systems.
• Competes with cysteine oxidation, S-nitrosylation, persulfidation and S-guanylation for the same thiol [1,4,5,6,8].
• Contributes to redox communication and cellular stress responses [1,5].
• Linked to cancer biology through dysregulated lipid modification of oncoproteins and tumor suppressors.
• Implicated in neurodegeneration where protein lipidation and mitochondrial quality control intersect [2,7].
• Relevant to infectious disease and parasite metabolism, as cysteine modifications affect metabolic enzymes.
• Provides a potential drug target for modulating protein localization and signaling.
• Essential for interpreting CRISPR screens that target lipid-modifying enzymes.
• Helps explain genotype-phenotype relationships in inherited disorders of lipid metabolism.
Molecular Mechanism of protein-cysteine S-stearoyltransferase activity
Substrate recognition and binding of octadecanoyl-CoA
In simple terms: The enzyme first grabs a stearate fat molecule that is attached to coenzyme A.
The reaction begins when the enzyme binds octadecanoyl-CoA, the activated lipid donor. The acyl-CoA binding site positions the thioester bond for nucleophilic attack by the cysteine thiol of the substrate protein. This step is analogous to other S-acyltransferases that use acyl-CoA donors, and it determines the specificity for the 18-carbon stearoyl chain.
Cysteine thiol activation and nucleophilic attack
In simple terms: The target cysteine on the protein becomes reactive and attacks the stearate, forming a new sulfur bond.
The cysteine residue of the substrate protein must be in a reactive thiolate form to attack the thioester carbonyl of octadecanoyl-CoA. This nucleophilic attack displaces coenzyme A and forms a covalent thioester bond between the stearoyl group and the cysteine sulfur. Because the same cysteine can also undergo oxidation, S-nitrosylation, persulfidation or S-guanylation, the local redox environment influences whether S-stearoylation occurs [1,4,5,6,8].
Formation of the S-octadecanoyl-L-cysteinyl protein product
In simple terms: The protein now carries a stearate tag on its cysteine, which can change where it goes in the cell.
The product of the reaction is an S-octadecanoyl-L-cysteinyl protein, in which the stearoyl group is covalently attached to the cysteine sulfur. This lipid modification increases the hydrophobicity of the protein and can promote association with membranes or specific membrane microdomains. The modification is reversible in principle, and its dynamics are part of the broader landscape of protein lipidation.
Cofactors and catalytic residues
In simple terms: The enzyme uses a catalytic pocket with key amino acids to speed up the reaction.
S-acyltransferases typically contain a conserved catalytic domain with a cysteine or histidine residue that participates in catalysis. The reaction does not require ATP directly because the energy is provided by the thioester bond of octadecanoyl-CoA. Metal ions or accessory proteins may modulate activity in specific enzyme families, but the core chemistry is a thioester exchange.
Regulation by redox and metabolic state
In simple terms: The cell's oxidative state and metabolism can turn this modification on or off.
Because the substrate cysteine is redox-sensitive, changes in reactive oxygen species and redox communication can alter the availability of the thiol for S-stearoylation [1,5]. Metabolic signals that control acyl-CoA levels also influence the reaction, as the donor lipid must be available. In parasites and other systems, iron deficiency and redox status affect cysteine modifications of metabolic enzymes, illustrating the integration of redox and lipid signaling.
Key Genes Involved in GO:0140439 protein-cysteine S-stearoyltransferase activity
The following genes and proteins are functionally connected to protein-cysteine S-stearoyltransferase activity, either as enzymes, substrates or redox regulators that influence cysteine modification.
| Gene | Major Role | Research Relevance |
|---|---|---|
| ZDHHC family | Palmitoyl and S-acyltransferases that catalyze protein lipidation | Model enzymes for studying S-acyltransferase mechanism and specificity |
| LYPLA1 | Depalmitoylase that removes acyl groups from cysteine | Counteracts S-acylation and helps define reversibility |
| APT1 | Lysophospholipase that depalmitoylates proteins | Regulates dynamic lipidation cycles |
| GNAI1 | G protein subunit subject to lipid modification | Model substrate for membrane targeting studies |
| RAS | Small GTPase whose lipidation controls signaling | Cancer relevance of protein lipidation |
| CD36 | Membrane protein involved in lipid uptake | Links lipid metabolism to protein modification |
| TLR4 | Immune receptor modulated by lipidation | Innate immune signaling and macrophage function |
| NLRP3 | Inflammasome component affected by lipidation | Inflammation and immune cell biology |
| LDHA | Metabolic enzyme with redox-sensitive cysteine | Cysteine modification affects enzyme activity |
| GmNTL1 | Transcription factor with redox-sensitive cysteine | Oxidation of cysteine regulates stress tolerance |
| Parkin | E3 ubiquitin ligase involved in mitophagy | Mitochondrial quality control and neurodegeneration |
| PINK1 | Kinase that activates Parkin | Mitophagy pathway and Parkinson's disease |
| KEAP1 | Redox sensor with reactive cysteines | Electrophile signaling and antioxidant response |
| NFE2L2 | Transcription factor regulated by KEAP1 | Oxidative stress response |
| CBS | Enzyme involved in persulfidation | Cysteine modification cross-talk |
| MPST | Enzyme contributing to persulfidation | Redox signaling and sulfur metabolism |
| TXN | Thioredoxin system controlling redox state | Regulates cysteine thiol availability |
How Is protein-cysteine S-stearoyltransferase activity Regulated?
The activity of protein-cysteine S-stearoyltransferases is regulated at multiple levels. Substrate availability of octadecanoyl-CoA depends on fatty acid metabolism and acyl-CoA synthetases, so metabolic state influences the reaction. The redox environment controls whether the target cysteine is in a thiolate form available for S-acylation or is instead oxidized, nitrosylated, persulfidated or guanylated [1,4,5,6,8]. Enzymes such as depalmitoylases can remove the lipid modification, creating a dynamic cycle. In immune cells, palmitate availability and lipidation enzymes control macrophage function, showing that nutritional and inflammatory signals converge on this pathway. Mitochondrial quality control pathways involving Parkin and PINK1 also intersect with redox and lipid signals, indicating that S-stearoylation may be part of a broader stress-response network.
protein-cysteine S-stearoyltransferase activity and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| RAS | Cancer | Knockout and point-mutation cell lines to test lipidation-dependent signaling |
| Parkin | Parkinson's disease and mitophagy | Knockout and knock-in models to study mitochondrial quality control |
| LDHA | Parasite metabolism and iron deficiency | Point-mutation of cysteine to test S-nitrosylation effects |
| TLR4 | Inflammation and innate immunity | Overexpression and knockout macrophages to assess lipidation |
| KEAP1 | Oxidative stress and cancer | Cysteine point mutants to study electrophile sensing |
Cancer and dysregulated lipid modification
Protein lipidation controls the localization and activity of oncoproteins and tumor suppressors, and altered S-acylation can promote proliferative signaling. Because RAS and other small GTPases require lipid modification for membrane targeting, enzymes that carry out GO:0140439 are candidate targets in cancers driven by these pathways. Studying S-stearoylation in cancer models can reveal whether specific acyl chains contribute to tumor growth.
Neurodegeneration and mitochondrial quality control
Mitochondrial dysfunction and impaired mitophagy are hallmarks of neurodegeneration, and Parkin-mediated mitophagy is sensitive to metabolic signals such as fumarate. Protein lipidation influences mitochondrial membrane dynamics and protein targeting, so dysregulated S-stearoylation could contribute to neuronal stress. Redox imbalance and cysteine modification cross-talk are also implicated in neurodegenerative processes [1,5].
Immune dysfunction and inflammation
Palmitate-driven protein lipidation controls macrophage function, affecting inflammatory signaling and pathogen responses. S-stearoylation may modulate immune receptors and inflammasome components, thereby influencing the intensity of innate immune responses. Redox and electrophile signaling at cysteine residues further shapes immune cell activation.
Infectious disease and parasite metabolism
In Trichomonas vaginalis, S-nitrosylation of cysteine enhances lactate dehydrogenase activity under iron deficiency, showing that cysteine modifications are critical for parasite metabolic adaptation. Similar principles may apply to S-stearoylation in pathogens, making these enzymes potential antiparasitic targets.
From protein-cysteine S-stearoyltransferase activity-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Is the enzyme required for substrate lipidation? | CRISPR knockout of the candidate S-stearoyltransferase |
| Does a specific cysteine mediate S-stearoylation? | Point mutation of the cysteine to alanine or serine |
| Can a tagged enzyme be tracked in cells? | Knock-in of an epitope tag at the endogenous locus |
| Does overexpression alter membrane targeting? | Overexpression of wild-type and catalytic-dead enzyme |
| Which pathways depend on the modification? | CRISPR library screening and bioinformatics analysis |
| Does redox state affect the modification? | Knockout or point-mutation combined with oxidative stress [1,5] |
How to Study the protein-cysteine S-stearoyltransferase activity Process
| Method | What It Measures | Typical Application |
|---|---|---|
| Acyl-biotin exchange | Levels of S-acylated proteins | Detecting S-stearoylation on candidate proteins |
| Click chemistry with alkynyl lipids | Incorporation of lipid analogs | Labeling newly S-acylated proteins |
| Mass spectrometry | Identification of modified cysteine residues | Mapping S-stearoylation sites |
| Tag-switch assay | Persulfidation and other cysteine modifications | Distinguishing competing cysteine modifications |
| CRISPR knockout screening | Genes required for a phenotype | Functional genomics of lipidation pathways |
| Bioinformatics pathway analysis | Enriched pathways and networks | Interpreting screen and proteomic data |
| Live-cell imaging | Subcellular localization dynamics | Tracking membrane targeting of substrates |
| Redox sensors | Intracellular oxidative state | Linking redox to cysteine modification [1,5] |
Proteomic detection of S-acylated proteins
Click chemistry and acyl-biotin exchange methods can capture and identify proteins carrying S-acyl modifications, including S-stearoylation. Mass spectrometry then maps the modified cysteine residues and quantifies changes between conditions. These approaches are essential for defining the substrate repertoire of GO:0140439.
Redox and cysteine modification profiling
Because cysteine thiols are targeted by multiple modifications, researchers use tag-switch and related methods to measure persulfidation and other cysteine modifications. These techniques help distinguish S-stearoylation from oxidation, S-nitrosylation and S-guanylation at the same residue [1,4,5,6,8]. Combining them with lipidation assays provides a comprehensive view of cysteine regulation.
Genetic screens and functional genomics
CRISPR knockout and library screens can identify genes required for S-stearoylation-dependent phenotypes. Bioinformatics analysis of screen hits reveals enriched pathways and candidate substrates. This approach is powerful for linking GO:0140439 to specific cellular functions.
Imaging and subcellular localization
Fluorescent tagging of substrate proteins and enzymes allows visualization of how S-stearoylation changes membrane association and trafficking. Live-cell imaging can capture dynamic changes in response to metabolic or redox signals [1,5]. These methods connect the biochemical activity to cellular behavior.
How CRISPR Can Be Used to Study GO:0140439 protein-cysteine S-stearoyltransferase activity
Knockout
CRISPR knockout of a candidate S-stearoyltransferase gene eliminates the enzyme and allows researchers to test whether S-stearoylation of specific substrates is lost. Knockout cells can be compared with wild-type cells in assays of membrane targeting, signaling and proliferation. This approach is the first step in establishing causality for GO:0140439.
Point Mutation
Point mutation of the catalytic cysteine or histidine in the enzyme, or of the acceptor cysteine in the substrate, can dissect the reaction mechanism. These mutants separate catalytic activity from scaffolding functions and help identify the exact residue modified. Point mutations are also useful for testing whether a specific cysteine modification competes with oxidation or nitrosylation [1,4,5,6,8].
Knock-in
Knock-in of an epitope tag or fluorescent protein at the endogenous locus enables tracking of the enzyme or substrate at physiological expression levels. Tagged knock-in models avoid artifacts from overexpression and allow localization studies. They are valuable for correlating S-stearoylation with subcellular dynamics.
Overexpression
Overexpression of wild-type or mutant enzyme can amplify the modification and reveal downstream phenotypes. Comparing wild-type and catalytically dead overexpression distinguishes enzymatic from non-enzymatic effects. This strategy is often used in combination with proteomics to identify substrates of GO:0140439.
How EDITGENE Supports protein-cysteine S-stearoyltransferase activity Research
Researchers studying protein-cysteine S-stearoyltransferase activity-related genes often need to determine whether a candidate gene is causally involved in a phenotype, which requires precise genetic models that isolate enzymatic function from other roles. EDITGENE provides CRISPR-based cell model services that enable knockout, point mutation, knock-in and overexpression of genes linked to GO:0140439, along with library screening and bioinformatics support to interpret the resulting data.
Contact EDITGENE today to design your custom CRISPR model for protein-cysteine S-stearoyltransferase activity research.
Frequently Asked Questions About protein-cysteine S-stearoyltransferase activity
What is protein-cysteine S-stearoyltransferase activity?
It is a molecular function (GO:0140439) that transfers a stearoyl group from octadecanoyl-CoA to a cysteine sulfur on a protein, forming an S-octadecanoyl-L-cysteinyl protein and releasing coenzyme A.
What is the GO ID for protein-cysteine S-stearoyltransferase activity?
The GO ID is GO:0140439, and it belongs to the molecular_function ontology.
What reaction does GO:0140439 catalyze?
It catalyzes octadecanoyl-CoA + L-cysteinyl-[protein] = CoA + S-octadecanoyl-L-cysteinyl-[protein].
What genes are involved in protein-cysteine S-stearoyltransferase activity?
Genes in the ZDHHC family and related S-acyltransferases are involved, along with depalmitoylases such as LYPLA1 and APT1 that reverse the modification.
How is S-stearoylation different from S-palmitoylation?
Both are S-acylation reactions, but S-stearoylation uses an 18-carbon stearoyl group, whereas S-palmitoylation uses a 16-carbon palmitoyl group; they share mechanistic features but differ in acyl chain specificity.
Why is cysteine important for this modification?
Cysteine provides a reactive thiol that can attack the acyl-CoA thioester, and the same thiol can also undergo oxidation, S-nitrosylation, persulfidation and S-guanylation, making it a hub for redox and lipid signaling [1,4,5,6,8].
What diseases are linked to protein lipidation?
Dysregulated protein lipidation has been linked to cancer, neurodegeneration and immune dysfunction, and cysteine modifications affect parasite metabolism [2,4,7].
How can I study protein-cysteine S-stearoyltransferase activity in the lab?
Common methods include acyl-biotin exchange, click chemistry with lipid analogs, mass spectrometry, tag-switch assays and CRISPR-based genetic screens [7,8].
What CRISPR models are useful for studying GO:0140439?
Knockout, point mutation, knock-in and overexpression models each address different questions about enzyme function, substrate specificity and downstream phenotypes.
Does redox state affect S-stearoylation?
Yes, because the target cysteine is redox-sensitive, changes in reactive oxygen species and redox communication can influence whether the thiol is available for S-stearoylation [1,5].
Conclusion
Protein-cysteine S-stearoyltransferase activity (GO:0140439) is a specialized lipidation reaction that attaches a stearoyl group to cysteine residues, influencing protein localization, signaling and metabolism. Its integration with redox and electrophile signaling at cysteine thiols makes it a key node in cellular stress responses and disease pathways [1,4,5,6,8]. CRISPR-based models and proteomic methods provide the tools needed to define its substrates and functions, and EDITGENE offers comprehensive services to accelerate this research.
References
- 1. Averill-Bates D. 2024. Reactive oxygen species and cell signaling. Review.. Biochim Biophys Acta Mol Cell Res 1871(2):119573 PMID: 37949302
- 2. Ham SJ et al.. 2025. Mitochondrial fumarate inhibits Parkin-mediated mitophagy.. Mol Cell 85(12):2287-2302.e9 PMID: 40505663
- 3. Zhang W et al.. 2023. H2O2-dependent oxidation of the transcription factor GmNTL1 promotes salt tolerance in soybean.. Plant Cell 36(1):112-135 PMID: 37770034
- 4. Cheng WH et al.. 2020. Protein cysteine S-nitrosylation provides reducing power by enhancing lactate dehydrogenase activity in Trichomonas vaginalis under iron deficiency.. Parasit Vectors 13(1):477 PMID: 32948226
- 5. Sies H. 2024. Dynamics of intracellular and intercellular redox communication.. Free Radic Biol Med 225:933-939 PMID: 39491734
- 6. Ahmed KA et al.. 2011. Protein cysteine S-guanylation and electrophilic signal transduction by endogenous nitro-nucleotides.. Amino Acids 41(1):123-30 PMID: 20213439
- 7. Guns J et al.. 2022. Protein Lipidation by Palmitate Controls Macrophage Function.. Cells 11(3) PMID: 35159374
- 8. Kouroussis E et al.. 2019. Measurement of Protein Persulfidation: Improved Tag-Switch Method.. Methods Mol Biol 2007:37-50 PMID: 31148105
