GO:0004822 isoleucine-tRNA ligase activity: Mechanism, Genes and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0004822 (isoleucine-tRNA ligase activity) catalyzes the attachment of L-isoleucine to tRNA(Ile), a critical step in protein synthesis.
• The enzyme, isoleucyl-tRNA synthetase (IARS), is a class I aminoacyl-tRNA synthetase that uses a two-step mechanism with an aminoacyl-adenylate intermediate.
• IARS is essential for translational fidelity and is targeted by natural antibiotics like mupirocin, making it a drug target.
• Mutations in IARS cause rare mitochondrial diseases such as Leigh syndrome and infantile liver failure.
• IARS is part of the multi-synthetase complex, linking translation to diverse cellular processes.
• CRISPR-based models (knockout, knock-in, point mutation) are powerful tools to study IARS function and disease mechanisms.
Description
Isoleucine-tRNA ligase activity (GO:0004822) is a molecular function that ensures the correct incorporation of the amino acid L-isoleucine into proteins during translation. This activity is carried out by the enzyme isoleucyl-tRNA synthetase (IARS), which charges tRNA(Ile) with isoleucine, thereby deciphering the genetic code. Accurate aminoacylation is vital for cellular proteostasis, and errors can lead to misfolded proteins and disease. Beyond its canonical role, IARS is implicated in mitochondrial translation, immune response, and is a target for antibiotics and potential therapeutics. Researchers study GO:0004822 to understand translation mechanisms, develop antimicrobials, and model rare genetic disorders.
isoleucine-tRNA ligase activity At A Glance
| GO ID | GO:0004822 |
|---|---|
| GO term | isoleucine-tRNA ligase activity |
| Ontology | molecular_function |
| Synonym | isoleucyl-tRNA synthetase activity |
| Major function | Catalyzes the attachment of L-isoleucine to tRNA(Ile) for protein synthesis |
| Reaction | L-isoleucine + ATP + tRNA(Ile) = L-isoleucyl-tRNA(Ile) + AMP + diphosphate + 2 H+ |
| EC number | 6.1.1.5 |
| Cofactors | ATP, Mg2+ |
| Localization | Cytoplasm and mitochondria |
What Is GO:0004822?
GO:0004822 describes the catalytic activity of isoleucine-tRNA ligase, which joins L-isoleucine to its cognate tRNA in a two-step reaction: first, isoleucine is activated by ATP to form isoleucyl-adenylate, releasing pyrophosphate; second, the activated amino acid is transferred to the 2'-OH of the terminal adenosine of tRNA(Ile), yielding L-isoleucyl-tRNA(Ile), AMP, and two protons.
Why Is isoleucine-tRNA ligase activity Important in Cell Biology?
Isoleucine-tRNA ligase activity is fundamental to protein synthesis and translational fidelity, as it ensures that isoleucine is correctly paired with its tRNA. Dysregulation of this activity is linked to mitochondrial diseases, cancer, and antibiotic resistance, making it a focal point for therapeutic development.
• Essential for accurate translation of the genetic code.
• Mutations in IARS cause rare mitochondrial diseases such as Leigh syndrome and infantile liver failure.
• Target of the antibiotic mupirocin, used to treat bacterial infections.
• Involved in the multi-synthetase complex, integrating translation with signaling.
• Plays a role in immune response and inflammation.
• Potential target for anticancer therapy due to altered expression in tumors.
• Key to understanding evolutionary adaptations in tRNA recognition.
• Model for studying enzyme superspecificity and editing mechanisms.
Molecular Mechanism of isoleucine-tRNA ligase activity
Substrate Recognition and Binding
In simple terms: The enzyme first grabs isoleucine and ATP, and finds the right tRNA.
Isoleucyl-tRNA synthetase (IARS) specifically recognizes L-isoleucine, ATP, and tRNA(Ile) through its catalytic domain and anticodon-binding domain. The enzyme discriminates against the similar amino acid valine via a editing site.
Amino Acid Activation
In simple terms: Isoleucine is activated by ATP to form a high-energy intermediate.
In the first step, IARS catalyzes the formation of isoleucyl-adenylate (Ile-AMP) from isoleucine and ATP, releasing pyrophosphate. This reaction requires Mg2+ and is driven by ATP hydrolysis.
tRNA Charging
In simple terms: The activated isoleucine is transferred onto the tRNA.
The activated isoleucine is transferred to the 2'-OH of the terminal adenosine of tRNA(Ile), forming L-isoleucyl-tRNA(Ile) and releasing AMP. This step ensures the covalent attachment of the amino acid to the tRNA.
Proofreading and Editing
In simple terms: The enzyme double-checks its work to avoid mistakes.
IARS possesses a editing domain that hydrolyzes mischarged tRNA, such as valyl-tRNA(Ile), to maintain translational fidelity. Some natural variants lack tRNA-dependent editing, highlighting diversity in proofreading mechanisms.
Regulation and Complex Formation
In simple terms: The enzyme works as part of a larger team and is controlled by cellular signals.
IARS is part of the multi-synthetase complex, which includes other synthetases and auxiliary proteins, and its activity can be regulated by post-translational modifications and cellular conditions.
Key Genes Involved in GO:0004822 isoleucine-tRNA ligase activity
The following genes and proteins are key players in isoleucine-tRNA ligase activity and its regulation.
| Gene | Major Role | Research Relevance |
|---|---|---|
| IARS1 | Cytoplasmic isoleucyl-tRNA synthetase | Mutations cause mitochondrial disease; target for inhibitors |
| IARS2 | Mitochondrial isoleucyl-tRNA synthetase | Associated with Leigh syndrome and liver failure |
| MARS | Methionyl-tRNA synthetase | Component of multi-synthetase complex |
| AIMP2 | Auxiliary protein in multi-synthetase complex | Regulates complex assembly and stability |
| EPRS | Glutamyl-prolyl-tRNA synthetase | Interacts with IARS in complex |
| KARS | Lysyl-tRNA synthetase | Component of multi-synthetase complex |
| RARS | Arginyl-tRNA synthetase | Component of multi-synthetase complex |
| QARS | Glutaminyl-tRNA synthetase | Component of multi-synthetase complex |
| DARS | Aspartyl-tRNA synthetase | Component of multi-synthetase complex |
| YARS | Tyrosyl-tRNA synthetase | Target of sulfamate inhibitors |
| LARS | Leucyl-tRNA synthetase | Component of multi-synthetase complex |
| VARS | Valyl-tRNA synthetase | Related to IARS editing |
| Mupirocin | Antibiotic targeting IARS | Used to study resistance mechanisms |
| tRNA(Ile) | Transfer RNA for isoleucine | Recognition by IARS |
| ATP | Energy source for aminoacylation | Cofactor in reaction |
| Mg2+ | Cofactor for catalysis | Required for ATP binding |
| Ile-AMP | Intermediate in reaction | Key to understanding mechanism |
How Is isoleucine-tRNA ligase activity Regulated?
Isoleucine-tRNA ligase activity is regulated at multiple levels. Its expression can be induced by amino acid starvation via the integrated stress response, and its activity is modulated by post-translational modifications and interaction with the multi-synthetase complex. Additionally, the enzyme's editing function is regulated by tRNA availability and cellular metabolic state.
isoleucine-tRNA ligase activity and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| IARS2 | Leigh syndrome, liver failure | Knockout mouse, patient-derived fibroblasts |
| IARS1 | Potential role in cancer | Cancer cell lines with overexpression/knockdown |
| IARS (bacterial) | Mupirocin resistance | Bacterial strains with point mutations |
| IARS variants | Translational fidelity defects | Yeast or human cell models |
Mitochondrial Diseases
Mutations in IARS2, the mitochondrial isoleucyl-tRNA synthetase, cause Leigh syndrome and infantile liver failure, highlighting the importance of isoleucine-tRNA ligase activity in mitochondrial translation.
Cancer
Dysregulated aminoacyl-tRNA synthetases, including IARS, are implicated in cancer progression and are being explored as therapeutic targets.
Infectious Diseases
Bacterial IARS is the target of mupirocin, and resistance mechanisms are studied to develop new antibiotics.
From isoleucine-tRNA ligase activity-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| What is the effect of IARS1 knockout on cell viability? | CRISPR knockout in HeLa or HEK293 cells |
| How do disease-associated point mutations affect IARS2 function? | Point mutation knock-in in patient iPSCs |
| Can we tag IARS1 to study its localization? | Knock-in of fluorescent tag (e.g., GFP) in cancer cells |
| What is the impact of IARS1 overexpression on translation? | Overexpression in mammalian cells |
| How does mupirocin resistance arise? | Bacterial knockout and point mutation libraries |
| What genes interact with IARS1? | CRISPR library screening with IARS1 as bait |
How to Study the isoleucine-tRNA ligase activity Process
| Method | What It Measures | Typical Application |
|---|---|---|
| Ribo-seq | Translation efficiency | Global protein synthesis changes |
| RNA-seq | Gene expression | Transcriptional response to IARS perturbation |
| Proteomics | Protein interactions, modifications | Identifying complex components |
| Imaging | Localization, dynamics | Subcellular distribution |
| Aminoacylation assay | Enzyme activity | Kinetic studies |
| Editing assay | Proofreading activity | Fidelity studies |
| CRISPR screen | Gene essentiality | Identifying synthetic lethality |
Ribo-seq
Ribosome profiling measures translation efficiency and can reveal changes in global protein synthesis upon IARS modulation.
RNA-seq
Transcriptomics can assess changes in gene expression, including tRNA and synthetase levels, in response to IARS perturbations.
Proteomics
Mass spectrometry can identify interacting proteins and post-translational modifications of IARS.
Imaging
Fluorescence microscopy of tagged IARS can reveal its subcellular localization and dynamics.
How CRISPR Can Be Used to Study GO:0004822 isoleucine-tRNA ligase activity
Knockout
CRISPR knockout of IARS1 or IARS2 can reveal essential roles in cell viability and mitochondrial function.
Point Mutation
Introducing disease-associated point mutations (e.g., in IARS2) via CRISPR can model Leigh syndrome and study molecular mechanisms.
Knock-in
Knock-in of tags (e.g., GFP) allows visualization and immunoprecipitation of IARS in live cells.
Overexpression
CRISPR activation or cDNA overexpression can study the effects of IARS upregulation on translation and disease.
How EDITGENE Supports isoleucine-tRNA ligase activity Research
Researchers studying isoleucine-tRNA ligase activity-related genes often need to determine whether a candidate gene is causally involved in translation, disease, or drug response. EDITGENE provides comprehensive CRISPR services to create precise cellular models for such investigations.
Contact EDITGENE today to design your custom CRISPR model for isoleucine-tRNA ligase activity research.
Frequently Asked Questions About isoleucine-tRNA ligase activity
What is isoleucine-tRNA ligase activity?
It is the enzymatic activity that attaches the amino acid isoleucine to its corresponding tRNA molecule, a crucial step in protein synthesis.
What genes are involved in isoleucine-tRNA ligase activity?
The main genes are IARS1 (cytoplasmic) and IARS2 (mitochondrial), which encode isoleucyl-tRNA synthetases.
What diseases are associated with isoleucine-tRNA ligase activity?
Mutations in IARS2 cause Leigh syndrome and infantile liver failure; bacterial IARS is targeted by mupirocin.
How is isoleucine-tRNA ligase activity regulated?
It is regulated by amino acid availability, post-translational modifications, and interaction with the multi-synthetase complex.
What is the reaction catalyzed by isoleucine-tRNA ligase?
L-isoleucine + ATP + tRNA(Ile) = L-isoleucyl-tRNA(Ile) + AMP + diphosphate + 2 H+.
What is the role of isoleucyl-tRNA synthetase in translation?
It ensures that isoleucine is correctly incorporated into proteins by charging tRNA(Ile) with high fidelity.
Can isoleucine-tRNA ligase be targeted by drugs?
Yes, it is the target of the antibiotic mupirocin and is being explored for anticancer therapy.
What are the synonyms for isoleucine-tRNA ligase activity?
Synonyms include isoleucyl-tRNA synthetase activity, isoleucine translase activity, and L-isoleucine:tRNAIle ligase (AMP-forming).
How can CRISPR be used to study isoleucine-tRNA ligase activity?
CRISPR can create knockouts, point mutations, and knock-ins in IARS genes to model diseases and study function.
What model systems are used to study isoleucine-tRNA ligase activity?
Common models include human cell lines, patient-derived fibroblasts, yeast, and bacteria.
Conclusion
Isoleucine-tRNA ligase activity (GO:0004822) is a cornerstone of protein synthesis, with critical roles in health and disease. Understanding its mechanism, regulation, and genetic underpinnings offers insights into mitochondrial disorders, cancer, and infectious diseases. Advanced CRISPR tools enable precise modeling of IARS-related pathologies, accelerating therapeutic discovery.
References
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- 3. Zivkovic I et al.. 2024. Exploring mechanisms of mupirocin resistance and hyper-resistance.. Biochem Soc Trans 52(3):1109-1120 PMID: 38884776
- 4. Lee SW et al.. 2004. Aminoacyl-tRNA synthetase complexes: beyond translation.. J Cell Sci 117(Pt 17):3725-34 PMID: 15286174
- 5. Uesugi G et al.. 2022. Recognition of tRNA(Ile) with a UAU anticodon by isoleucyl-tRNA synthetase in lactic acid bacteria.. FEBS J 289(16):4888-4900 PMID: 35122395
- 6. Favorova OO. 1984. [Superspecificity of aminoacyl-tRNA-synthases].. Mol Biol (Mosk) 18(1):205-26 PMID: 6423966
- 7. De Ruysscher D et al.. 2020. Phenyltriazole-functionalized sulfamate inhibitors targeting tyrosyl- or isoleucyl-tRNA synthetase.. Bioorg Med Chem 28(15):115580 PMID: 32631562
- 8. Cvetesic N et al.. 2016. Naturally Occurring Isoleucyl-tRNA Synthetase without tRNA-dependent Pre-transfer Editing.. J Biol Chem 291(16):8618-31 PMID: 26921320
