GO:0008113 peptide-methionine (S)-S-oxide reductase activity: Mechanism, Genes and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0008113 describes the enzymatic activity that reduces the S-stereoisomer of oxidized methionine in proteins, restoring methionine residues and protecting cells from oxidative damage.
• This activity is catalyzed by methionine sulfoxide reductase A (MSRA) enzymes, which use thioredoxin as a reducing agent to convert methionine sulfoxide back to methionine.
• Methionine oxidation is a reversible post-translational modification that can regulate protein function, and its reduction by MSRA is critical for redox homeostasis.
• Dysregulation of MSRA has been implicated in cancer metastasis, neurodegenerative diseases, and aging-related processes.
• Studying GO:0008113 requires methods such as enzyme activity assays, mass spectrometry, and CRISPR-based gene editing to manipulate MSRA genes.
• EDITGENE provides CRISPR services including knockout, point mutation, knock-in, and overexpression to model MSRA-related biology.
Description
Peptide-methionine (S)-S-oxide reductase activity (GO:0008113) is a molecular function that catalyzes the reduction of the S-stereoisomer of methionine sulfoxide in proteins back to methionine, using thioredoxin as an electron donor. This activity is essential for repairing oxidative damage to proteins, as methionine residues are highly susceptible to oxidation by reactive oxygen species. The enzyme responsible, methionine sulfoxide reductase A (MSRA), specifically reduces the S-form of methionine sulfoxide, while MSRB reduces the R-form. This stereospecificity is crucial for maintaining protein function and cellular redox balance. Researchers study GO:0008113 to understand how cells counteract oxidative stress, and its dysfunction has been linked to cancer, neurodegeneration, and aging. The reversible oxidation of methionine is now recognized as a regulatory post-translational modification, with MSRA playing a key role in signal transduction and protein stability.
peptide-methionine (S)-S-oxide reductase activity At A Glance
| GO ID | GO:0008113 |
|---|---|
| GO term | peptide-methionine (S)-S-oxide reductase activity |
| Ontology | molecular_function |
| Synonym | methionine sulfoxide (protein) reductase activity; peptide-methionine-(S)-S-oxide reductase activity; protein-methionine-S-oxide reductase activity |
| Major function | Reduction of S-methionine sulfoxide in proteins to methionine, using thioredoxin as an electron donor |
| Reaction | L-methionyl-[protein] + [thioredoxin]-disulfide + H2O = L-methionyl-(S)-S-oxide-[protein] + [thioredoxin]-dithiol |
| Enzyme class | Oxidoreductase (EC 1.8.4.11) |
| Cofactor | Thioredoxin (recycling system) |
| Subcellular location | Cytoplasm, mitochondria (for MSRA variants) |
What Is GO:0008113?
GO:0008113, peptide-methionine (S)-S-oxide reductase activity, is defined as the catalysis of the reaction: L-methionyl-[protein] + [thioredoxin]-disulfide + H2O = L-methionyl-(S)-S-oxide-[protein] + [thioredoxin]-dithiol. In simpler terms, it is the enzyme activity that reduces oxidized methionine (specifically the S-enantiomer) in proteins, using thioredoxin as a reductant, thereby repairing oxidative damage and restoring protein function.
Why Is peptide-methionine (S)-S-oxide reductase activity Important in Cell Biology?
GO:0008113 is important because it maintains protein function by reversing oxidative damage to methionine residues, which are among the most oxidation-prone amino acids. This activity protects cells from oxidative stress, regulates enzyme activity, and modulates signal transduction pathways. Dysregulation of this activity has been linked to cancer progression, neurodegenerative disorders, and aging. Understanding GO:0008113 provides insights into redox biology and offers potential therapeutic targets for diseases associated with oxidative stress.
• Protects proteins from irreversible oxidative damage by reducing methionine sulfoxide.
• Regulates protein function through reversible methionine oxidation, a post-translational modification.
• Plays a role in cancer metastasis, as methionine oxidation can activate pyruvate kinase M2.
• Implicated in neurodegenerative diseases such as Alzheimer's and Parkinson's, where oxidative stress is a hallmark.
• Contributes to aging processes by maintaining redox homeostasis.
• Serves as a model for studying stereospecific enzyme mechanisms.
• Potential target for developing antioxidants and anti-aging therapies.
• Essential for bacterial pathogenesis and survival under oxidative stress.
• Used in biotechnology for chiral resolution of sulfoxides.
• Provides a paradigm for understanding selenoprotein function (MSRB1).
Molecular Mechanism of peptide-methionine (S)-S-oxide reductase activity
Substrate Recognition and Binding
In simple terms: The enzyme finds and grabs onto the oxidized methionine in proteins.
MSRA specifically recognizes the S-stereoisomer of methionine sulfoxide within peptide substrates. The enzyme binds to the oxidized methionine residue through a conserved active site pocket, facilitating nucleophilic attack by a cysteine residue. This stereospecificity ensures that only the S-form is reduced, while the R-form is handled by MSRB.
Catalytic Mechanism
In simple terms: A chemical reaction occurs that removes oxygen from the oxidized methionine.
The catalytic cycle involves a conserved cysteine residue (Cys) that attacks the sulfoxide oxygen, forming a sulfenic acid intermediate. This intermediate is then reduced by thioredoxin, regenerating the active enzyme and producing methionine. The reaction consumes thioredoxin and water, releasing thioredoxin disulfide and methionine.
Thioredoxin Recycling System
In simple terms: Thioredoxin acts as a rechargeable battery for the enzyme.
Thioredoxin is oxidized during the reduction of methionine sulfoxide and must be recycled by thioredoxin reductase using NADPH. This system ensures a continuous supply of reducing equivalents for MSRA activity. The thioredoxin system is essential for maintaining MSRA function under oxidative stress conditions.
Regulation by Oxidative Stress
In simple terms: The enzyme's activity can be turned up or down depending on the cell's stress levels.
MSRA expression and activity are regulated in response to oxidative stress. For example, in bacteria, MSRA is induced under oxidative conditions to protect proteins. In mammalian cells, MSRA activity can be modulated by post-translational modifications and interacting proteins.
Key Genes Involved in GO:0008113 peptide-methionine (S)-S-oxide reductase activity
The following genes encode proteins that catalyze or support peptide-methionine (S)-S-oxide reductase activity.
| Gene | Major Role | Research Relevance |
|---|---|---|
| MSRA | Catalyzes reduction of S-methionine sulfoxide in proteins | Central enzyme for GO:0008113; knockout models show increased oxidative stress |
| MSRB1 | Reduces R-methionine sulfoxide; selenoprotein | Complementary to MSRA; studied for selenium biology |
| TXNRD1 | Thioredoxin reductase, recycles thioredoxin | Supports MSRA activity by maintaining reduced thioredoxin |
| TXN | Thioredoxin, electron donor for MSRA | Directly provides reducing equivalents for GO:0008113 |
| TXN2 | Mitochondrial thioredoxin | Supports mitochondrial MSRA activity |
| NCF1 | Regulates oxidative burst | Affects methionine oxidation levels |
| PKM | Pyruvate kinase M2, regulated by methionine oxidation | Methionine oxidation activates PKM2, promoting cancer metastasis |
| SOD1 | Superoxide dismutase, reduces ROS | Indirectly affects methionine oxidation |
| CAT | Catalase, detoxifies hydrogen peroxide | Reduces oxidative stress that leads to methionine oxidation |
| GPX1 | Glutathione peroxidase | Protects against oxidative damage |
| PRDX1 | Peroxiredoxin, reduces peroxides | Contributes to redox balance |
| MSRA (bacterial) | Bacterial MSRA homolog | Model for studying enzyme mechanism |
| MsrA (Drosophila) | Drosophila MSRA | Lacks methionine oxidase activity, studied for substrate specificity |
| MsrB (Drosophila) | Drosophila MSRB | Reduces R-form, complementary to MSRA |
| TrxR (bacterial) | Thioredoxin reductase in bacteria | Essential for MSRA recycling |
| TrxA (bacterial) | Thioredoxin in bacteria | Electron donor for bacterial MSRA |
| Selenoprotein K | May interact with MSRB1 | Potential role in redox regulation |
| MICAL | Methionine monooxygenase | Oxidizes methionine, opposing MSRA |
How Is peptide-methionine (S)-S-oxide reductase activity Regulated?
The activity of peptide-methionine (S)-S-oxide reductase is regulated at multiple levels. Transcriptionally, MSRA expression is induced by oxidative stress through transcription factors such as Nrf2. Post-translationally, MSRA activity can be modulated by phosphorylation and other modifications. The availability of thioredoxin, which is regulated by thioredoxin reductase and NADPH, also controls MSRA activity. Additionally, methionine oxidation itself can act as a regulatory switch, with MSRA reversing this modification to modulate protein function.
peptide-methionine (S)-S-oxide reductase activity and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| MSRA | Cancer metastasis, oxidative stress | Knockout in cancer cell lines, xenograft models |
| MSRA | Neurodegeneration | Neuron-specific knockout mice, oxidative stress induction |
| MSRB1 | Selenium-related disorders | Knockout mice, selenoprotein studies |
| PKM | Pancreatic cancer | Point mutation of methionine oxidation sites, knock-in mice |
| TXN | Inflammatory diseases | Thioredoxin knockout, overexpression models |
Cancer
Methionine oxidation activates pyruvate kinase M2 (PKM2), promoting pancreatic cancer metastasis, and MSRA counteracts this by reducing oxidized methionine. Dysregulation of MSRA has been observed in various cancers, suggesting a role in tumor progression.
Neurodegenerative Diseases
Oxidative stress is a hallmark of neurodegenerative diseases such as Alzheimer's and Parkinson's. MSRA protects neurons by repairing oxidized methionine residues, and its dysfunction may contribute to disease pathogenesis.
Aging
MSRA activity declines with age, leading to accumulation of oxidized proteins and cellular dysfunction. Caloric restriction and other anti-aging interventions may upregulate MSRA.
Bacterial Infections
Bacterial MSRA is important for survival under oxidative stress imposed by the host immune system. Inhibiting MSRA could be a strategy for developing new antibiotics.
From peptide-methionine (S)-S-oxide reductase activity-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Does MSRA knockout increase oxidative stress? | MSRA knockout cell lines and mice |
| How does methionine oxidation regulate PKM2? | Point mutation of PKM2 methionine residues, knock-in mice |
| What is the role of MSRA in neurodegeneration? | Neuron-specific MSRA knockout mice |
| Can MSRA overexpression protect against oxidative damage? | MSRA overexpression cell lines and transgenic mice |
| How does bacterial MSRA contribute to virulence? | Bacterial MSRA knockout strains |
| What is the substrate specificity of MSRA? | Recombinant MSRA with mutant substrates, in vitro assays |
How to Study the peptide-methionine (S)-S-oxide reductase activity Process
| Method | What It Measures | Typical Application |
|---|---|---|
| Enzyme activity assay | MSRA catalytic activity | Quantifying GO:0008113 in cell lysates |
| Mass spectrometry | Methionine oxidation sites | Proteome-wide analysis of oxidized proteins |
| CRISPR-Cas9 knockout | Gene function | Studying loss of MSRA in cells and mice |
| Western blot | Protein expression levels | Detecting MSRA protein in samples |
| qRT-PCR | mRNA expression | Measuring MSRA transcription |
| Fluorescent probes | Methionine sulfoxide levels | Live-cell imaging of oxidative stress |
| Thioredoxin reductase assay | Thioredoxin recycling | Measuring cofactor regeneration |
| Site-directed mutagenesis | Enzyme mechanism | Identifying catalytic residues |
Enzyme Activity Assays
MSRA activity can be measured using spectrophotometric assays that monitor the reduction of methionine sulfoxide or the oxidation of NADPH via the thioredoxin system. These assays are essential for quantifying GO:0008113 in cell lysates or purified enzyme preparations.
Mass Spectrometry
Mass spectrometry-based proteomics can identify and quantify methionine oxidation sites in proteins, providing a global view of the substrates and impact of MSRA activity. This method is crucial for understanding the reversible nature of methionine oxidation.
CRISPR-Cas9 Gene Editing
CRISPR-Cas9 can be used to generate MSRA knockout, point mutant, or knock-in cell lines to study the function of GO:0008113 in various biological contexts. These models allow for precise manipulation of the gene and its activity.
Fluorescent Imaging
Genetically encoded fluorescent probes can detect methionine sulfoxide levels in live cells, enabling real-time monitoring of MSRA activity and oxidative stress.
How CRISPR Can Be Used to Study GO:0008113 peptide-methionine (S)-S-oxide reductase activity
Knockout
CRISPR knockout of MSRA can be achieved by introducing indels in the coding sequence, leading to loss of enzyme activity. Such models are used to study the consequences of GO:0008113 deficiency, including increased oxidative stress and protein damage.
Point Mutation
Point mutations in the catalytic cysteine residue of MSRA can abolish its activity, allowing researchers to dissect the enzymatic mechanism and its physiological roles. CRISPR can introduce these specific mutations in cell lines or animal models.
Knock-in
Knock-in of tagged MSRA (e.g., GFP or FLAG) enables visualization and purification of the enzyme, facilitating studies of its localization, interactions, and dynamics. CRISPR-mediated knock-in ensures endogenous expression levels.
Overexpression
CRISPR activation (CRISPRa) or transgenic overexpression of MSRA can be used to study the protective effects of increased GO:0008113 activity against oxidative stress and disease.
How EDITGENE Supports peptide-methionine (S)-S-oxide reductase activity Research
Researchers studying peptide-methionine (S)-S-oxide reductase activity-related genes often need to determine whether a candidate gene is causally involved in oxidative stress responses, protein regulation, or disease. EDITGENE provides comprehensive CRISPR-based services to create precise cellular and animal models for such investigations.
Contact EDITGENE today to design your custom CRISPR model for peptide-methionine (S)-S-oxide reductase activity research.
Frequently Asked Questions About peptide-methionine (S)-S-oxide reductase activity
What is peptide-methionine (S)-S-oxide reductase activity?
It is an enzyme activity (GO:0008113) that reduces the S-stereoisomer of methionine sulfoxide in proteins back to methionine, using thioredoxin as a reductant.
What genes are involved in peptide-methionine (S)-S-oxide reductase activity?
The primary gene is MSRA, which encodes methionine sulfoxide reductase A. Other supporting genes include TXN, TXNRD1, and MSRB1.
What is the function of GO:0008113?
It repairs oxidative damage to proteins by reducing oxidized methionine residues, thereby maintaining protein function and cellular redox balance.
How is peptide-methionine (S)-S-oxide reductase activity measured?
It can be measured using enzyme activity assays that monitor NADPH oxidation or methionine sulfoxide reduction, often coupled with thioredoxin.
What diseases are associated with MSRA dysfunction?
MSRA dysfunction has been linked to cancer, neurodegenerative diseases, and aging-related disorders.
What is the difference between MSRA and MSRB?
MSRA reduces the S-form of methionine sulfoxide, while MSRB reduces the R-form. They are stereospecific and complementary.
Can CRISPR be used to study peptide-methionine (S)-S-oxide reductase activity?
Yes, CRISPR knockout, point mutation, and knock-in models can be used to manipulate MSRA and study its function.
What is the role of thioredoxin in GO:0008113?
Thioredoxin serves as the electron donor for MSRA, becoming oxidized in the process and requiring recycling by thioredoxin reductase.
Is methionine oxidation reversible?
Yes, methionine oxidation is reversible through the action of MSRA and MSRB, making it a regulatory post-translational modification.
How does oxidative stress affect MSRA activity?
Oxidative stress can induce MSRA expression and activity as a protective response, but excessive stress may overwhelm the system.
Conclusion
Peptide-methionine (S)-S-oxide reductase activity (GO:0008113) is a critical enzymatic function that protects proteins from oxidative damage by reducing methionine sulfoxide. Its role in redox regulation, disease, and aging makes it a significant research target. Understanding its mechanism and regulation offers potential therapeutic avenues for oxidative stress-related diseases.
References
- 1. Lu J et al.. 2014. The thioredoxin antioxidant system.. Free Radic Biol Med 66:75-87 PMID: 23899494
- 2. He D et al.. 2022. Methionine oxidation activates pyruvate kinase M2 to promote pancreatic cancer metastasis.. Mol Cell 82(16):3045-3060.e11 PMID: 35752173
- 3. Tarafdar S et al.. 2019. Drosophila methionine sulfoxide reductase A (MSRA) lacks methionine oxidase activity.. Free Radic Biol Med 131:154-161 PMID: 30529269
- 4. Boschi-Muller S et al.. 2014. Methionine sulfoxide reductase: chemistry, substrate binding, recycling process and oxidase activity.. Bioorg Chem 57:222-230 PMID: 25108804
- 5. Tarrago L et al.. 2018. Monitoring of Methionine Sulfoxide Content and Methionine Sulfoxide Reductase Activity.. Methods Mol Biol 1661:285-299 PMID: 28917052
- 6. Tarrago L et al.. 2022. The selenoprotein methionine sulfoxide reductase B1 (MSRB1).. Free Radic Biol Med 191:228-240 PMID: 36084791
- 7. Manta B et al.. 2017. Regulated methionine oxidation by monooxygenases.. Free Radic Biol Med 109:141-155 PMID: 28229915
- 8. Vincent MS et al.. 2023. Methionine oxidation in bacteria: A reversible post-translational modification.. Mol Microbiol 119(2):143-150 PMID: 36350090
