GO:0004077 biotin--[biotin carboxyl-carrier protein] ligase activity: Mechanism, Genes and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0004077 describes the enzymatic activity that covalently attaches biotin to a specific lysine residue on a biotin carboxyl-carrier protein (BCCP), using ATP and releasing AMP and diphosphate.
• This activity is essential for the function of biotin-dependent carboxylases, which participate in fatty acid synthesis, gluconeogenesis, and amino acid catabolism.
• The reaction proceeds through an ATP-grasp fold that activates biotin to biotinyl-5'-AMP before transferring it to the target protein.
• Biotin protein ligases (BPLs) can be extraordinarily specific or promiscuous, and this selectivity is a major research focus.
• Dysregulation of biotin attachment is linked to metabolic disorders and is exploited in proximity-labeling technologies such as AirID.
• CRISPR-based knockout, point-mutation, and knock-in models are powerful tools to dissect the physiological roles of this ligase activity.
Description
Biotin--[biotin carboxyl-carrier protein] ligase activity (GO:0004077) is a molecular function that catalyzes the covalent attachment of biotin to a conserved lysine residue on a biotin carboxyl-carrier protein (BCCP). This post-translational modification is essential for the catalytic activity of biotin-dependent enzymes, including acetyl-CoA carboxylase and pyruvate carboxylase, which are central to fatty acid synthesis, gluconeogenesis, and energy metabolism. The reaction consumes ATP and produces AMP and diphosphate, a hallmark of ATP-grasp enzymes. Researchers study this activity because it represents a critical node in metabolic regulation and because its mechanism is shared across all kingdoms of life. In humans, the enzyme responsible for this activity is holocarboxylase synthetase (HCS), also known as biotin protein ligase (BPL). Defects in biotin attachment lead to multiple carboxylase deficiency, a severe metabolic disorder. Beyond metabolism, engineered biotin ligases such as AirID are used for proximity-dependent biotinylation to map protein-protein interactions in living cells. Understanding GO:0004077 therefore bridges fundamental enzymology, metabolic disease, and modern proteomic tool development. This article synthesizes authoritative QuickGO data and verified PubMed literature to provide a research-grade overview of the mechanism, key genes, disease links, and experimental strategies for studying this activity.
biotin--[biotin carboxyl-carrier protein] ligase activity At A Glance
| GO ID | GO:0004077 |
|---|---|
| GO term | biotin--[biotin carboxyl-carrier protein] ligase activity |
| Ontology | molecular_function |
| Synonym | biotin holoenzyme synthetase activity; biotin--protein ligase activity; HCS; acetyl-CoA carboxylase biotin holoenzyme synthetase activity |
| Major function | Covalently attaches biotin to a conserved lysine on biotin carboxyl-carrier proteins, activating carboxylases. |
| Reaction | ATP + biotin + L-lysyl-[protein] = AMP + diphosphate + H+ + N(6)-biotinyl-L-lysyl-[protein]. |
| Enzyme class | ATP-grasp fold; ligase (AMP-forming). |
| Subcellular location | Cytoplasm and mitochondria, depending on the target carboxylase. |
| Related diseases | Multiple carboxylase deficiency, metabolic disorders. |
What Is GO:0004077?
GO:0004077 is defined as the catalysis of the reaction: ATP + biotin + L-lysyl-[protein] = AMP + diphosphate + H+ + N(6)-biotinyl-L-lysyl-[protein]. In simpler terms, it is the enzyme activity that attaches a biotin molecule to a specific lysine residue on a target protein, using ATP as an energy source and releasing AMP and diphosphate as byproducts. This activity is synonymous with biotin holoenzyme synthetase, biotin--protein ligase, and holocarboxylase synthetase (HCS).
Why Is biotin--[biotin carboxyl-carrier protein] ligase activity Important in Cell Biology?
GO:0004077 is fundamentally important because biotinylation of carboxyl-carrier proteins is a prerequisite for the function of essential metabolic enzymes such as acetyl-CoA carboxylase and pyruvate carboxylase. Without this modification, these enzymes cannot catalyze key reactions in fatty acid synthesis, gluconeogenesis, and amino acid catabolism, leading to severe metabolic consequences. Moreover, the mechanism of this ligase activity has been adapted for powerful research tools like proximity-dependent biotinylation, which enables mapping of protein interactions in living cells.
• Essential for fatty acid synthesis via acetyl-CoA carboxylase activation.
• Required for gluconeogenesis through pyruvate carboxylase biotinylation.
• Defects cause multiple carboxylase deficiency, a life-threatening metabolic disorder.
• Serves as a paradigm for ATP-grasp enzyme mechanism and substrate specificity.
• Engineered biotin ligases (e.g., AirID) enable proximity labeling for interactome mapping.
• Target for antibiotic and herbicide development in pathogens and plants.
• Plays a role in protein trafficking studies when used as a tagging system.
• Biotin attachment is highly regulated and can be specific or promiscuous depending on the organism.
• Provides a model for studying post-translational modification and enzyme-substrate recognition.
• Relevant to biotechnology applications in metabolic engineering and synthetic biology.
What Happens During biotin--[biotin carboxyl-carrier protein] ligase activity?
Substrate recognition and binding
In simple terms: The enzyme first grabs the biotin molecule and the target protein.
The biotin protein ligase (BPL) binds biotin and ATP in its active site, which adopts an ATP-grasp fold. It also recognizes the biotin carboxyl-carrier protein (BCCP) domain of the target carboxylase through specific structural features. In some organisms, the BCCP domain is fused to the biotin carboxylase domain, as seen in Chloroflexus aurantiacus acetyl-CoA carboxylase. The specificity of this recognition determines whether the ligase is extraordinarily specific or promiscuous.
Activation of biotin to biotinyl-5'-AMP
In simple terms: The enzyme uses ATP to make a reactive form of biotin.
ATP and biotin react to form biotinyl-5'-AMP, an activated intermediate, releasing diphosphate. This step is characteristic of ATP-grasp enzymes, which catalyze the formation of an amide bond between the carboxyl group of biotin and the epsilon-amino group of a lysine residue on the target protein. The reaction requires a divalent metal ion, typically Mg2+, for ATP coordination.
Transfer of biotin to the target lysine
In simple terms: The activated biotin is attached to the target protein.
The biotinyl group is transferred from biotinyl-5'-AMP to a specific lysine residue on the BCCP domain, forming an amide bond and releasing AMP. This covalent modification converts the apocarboxylase into its active holoenzyme form. The reaction is highly conserved across species, from bacteria to humans. In humans, the enzyme responsible is holocarboxylase synthetase (HCS), which biotinylates multiple carboxylases.
Post-biotinylation folding and function
In simple terms: Once biotin is attached, the protein can do its job.
After biotinylation, the BCCP domain swings biotin into the active site of the carboxylase to carry out carboxylation reactions. This structural flexibility is essential for catalysis. In pyruvate carboxylase, the biotinylated domain shuttles between the biotin carboxylase and carboxyltransferase sites. Defects in this process lead to inactive carboxylases and metabolic disease.
Key Genes Involved in GO:0004077 biotin--[biotin carboxyl-carrier protein] ligase activity
The following genes encode proteins that either possess biotin--[biotin carboxyl-carrier protein] ligase activity, are targets of this activity, or are directly involved in the biotinylation pathway.
| Gene | Major Role | Research Relevance |
|---|---|---|
| HLCS | Human holocarboxylase synthetase; catalyzes biotin attachment to carboxylases | Mutations cause multiple carboxylase deficiency; target for metabolic disease research. |
| BPL (E. coli birA) | Bifunctional biotin protein ligase and repressor | Model for studying enzyme specificity and regulation. |
| ACC1 (ACACA) | Acetyl-CoA carboxylase 1; accepts biotin for fatty acid synthesis | Key target for obesity and cancer metabolism studies. |
| ACC2 (ACACB) | Acetyl-CoA carboxylase 2; regulates fatty acid oxidation | Potential target for diabetes and metabolic syndrome. |
| PC | Pyruvate carboxylase; requires biotin for gluconeogenesis | Defects cause lactic acidosis and hypoglycemia. |
| PCCB | Propionyl-CoA carboxylase beta subunit; biotin-dependent | Mutations cause propionic acidemia. |
| MCCC1 | Methylcrotonoyl-CoA carboxylase alpha subunit; biotin-dependent | Defects cause 3-methylcrotonyl-CoA carboxylase deficiency. |
| MCCC2 | Methylcrotonoyl-CoA carboxylase beta subunit; biotin-dependent | Research model for organic acidemias. |
| BTD | Biotinidase; recycles biotin from biocytin | Deficiency causes biotin-responsive disorders. |
| SLC5A6 | Sodium-dependent multivitamin transporter; biotin uptake | Affects biotin availability for ligase activity. |
| BCCP (bacterial) | Biotin carboxyl-carrier protein domain | Target for structural and mechanistic studies. |
| AirID | Engineered biotin ligase for proximity labeling | Used to map protein-protein interactions in cells. |
| TurboID | Engineered biotin ligase for proximity labeling | Enables proteomic mapping of subcellular compartments. |
| BioID | Engineered biotin ligase for proximity labeling | Identifies weak or transient interactions in vivo. |
| HCS (yeast) | Yeast biotin protein ligase | Model for studying biotinylation in eukaryotes. |
| BirA (bacteria) | Biotin protein ligase in E. coli | Classic model for enzyme kinetics and regulation. |
How Is biotin--[biotin carboxyl-carrier protein] ligase activity Regulated?
The activity of biotin--[biotin carboxyl-carrier protein] ligase is regulated at multiple levels. In bacteria, the bifunctional BirA protein acts as a repressor of biotin biosynthesis genes when biotinyl-5'-AMP is abundant, linking ligase activity to transcriptional control. In humans, holocarboxylase synthetase (HCS) expression and activity can be influenced by biotin availability and metabolic status. Additionally, the specificity of the ligase for its target proteins is tightly controlled; some ligases are extraordinarily specific, while others exhibit promiscuous biotinylation, which can be exploited for proximity labeling. Post-translational modifications and cellular localization also modulate ligase function.
biotin--[biotin carboxyl-carrier protein] ligase activity and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| HLCS | Multiple carboxylase deficiency | Knockout or point-mutation in human cell lines; rescue with wild-type HLCS. |
| PC | Pyruvate carboxylase deficiency | Knock-in of patient mutations in iPSC-derived hepatocytes. |
| PCCB | Propionic acidemia | CRISPR knockout in HepG2 cells; metabolic profiling. |
| ACACA | Cancer metabolism, fatty acid synthesis | Overexpression and knockout in cancer cell lines; lipidomics. |
| BTD | Biotinidase deficiency | Knockout in HEK293; biotin recycling assays. |
Multiple carboxylase deficiency
Mutations in HLCS, the gene encoding human holocarboxylase synthetase, cause multiple carboxylase deficiency, an autosomal recessive disorder characterized by impaired activity of all biotin-dependent carboxylases. Patients present with metabolic acidosis, lethargy, and developmental delay. The disease highlights the essential role of GO:0004077 in human metabolism.
Metabolic disorders and organic acidemias
Defects in biotin-dependent carboxylases, such as propionyl-CoA carboxylase and methylcrotonoyl-CoA carboxylase, lead to organic acidemias. Although these are not directly caused by ligase mutations, the biotinylation activity of HCS is required for their function, making GO:0004077 a modifier of disease severity.
Cancer metabolism
Acetyl-CoA carboxylase, a major target of biotinylation, is often upregulated in cancers to support fatty acid synthesis. Inhibiting biotin attachment could therefore be a therapeutic strategy, and research into GO:0004077 may inform drug development.
From biotin--[biotin carboxyl-carrier protein] ligase activity-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Does loss of HLCS impair carboxylase activity? | HLCS knockout in HEK293 or HepG2 cells. |
| What is the effect of a specific patient mutation on ligase activity? | Point mutation knock-in using CRISPR in patient-derived fibroblasts. |
| Can a tagged HLCS be used to track localization? | Knock-in of FLAG- or GFP-tagged HLCS. |
| Does overexpression of ACC1 increase fatty acid synthesis? | Overexpression of ACACA in cancer cell lines. |
| Can proximity labeling identify novel interactors of BCCP? | Knock-in of AirID-tagged BCCP. |
| Is the ligase essential for bacterial growth? | CRISPR interference or knockout in E. coli. |
How to Study the biotin--[biotin carboxyl-carrier protein] ligase activity Process
| Method | What It Measures | Typical Application |
|---|---|---|
| Proximity labeling (AirID/TurboID) | Protein-protein interactions and subcellular proteomes | Mapping interactors of biotinylated proteins. |
| Western blot with streptavidin-HRP | Levels of biotinylated proteins | Assessing ligase activity in cell lysates. |
| 13C metabolic flux analysis | Activity of biotin-dependent carboxylases | Measuring gluconeogenesis and lipogenesis. |
| CRISPR knockout screens | Gene essentiality and synthetic lethality | Identifying modifiers of biotin metabolism. |
| X-ray crystallography | Three-dimensional structure of ligase-substrate complexes | Understanding catalytic mechanism. |
| RNA-seq | Transcriptional changes upon ligase perturbation | Identifying compensatory pathways. |
| Immunofluorescence | Subcellular localization of ligase and targets | Validating mitochondrial vs cytoplasmic pools. |
| Biotinylation assays with recombinant enzymes | Kinetic parameters and substrate specificity | Enzyme characterization. |
Proteomic mapping by proximity labeling
Engineered biotin ligases such as AirID and TurboID are used to biotinylate nearby proteins in living cells, enabling proteomic mapping of protein-protein interactions and subcellular compartments. These methods rely on the same chemistry as GO:0004077 but are repurposed for interactome discovery.
Metabolic flux analysis
Measuring the activity of biotin-dependent carboxylases through isotope-labeled substrates can reveal the functional impact of ligase activity. For example, 13C-bicarbonate incorporation into malate or lipids reflects pyruvate carboxylase and acetyl-CoA carboxylase activity.
Structural biology
X-ray crystallography and cryo-EM have elucidated the ATP-grasp fold and substrate binding of biotin protein ligases. Structures of BCCP domains in complex with ligases provide insights into specificity.
Genetic screens
CRISPR knockout libraries can be used to identify genes that modify sensitivity to biotin deprivation or ligase inhibitors. Such screens can uncover synthetic lethal interactions relevant to metabolic disease.
How CRISPR Can Be Used to Study GO:0004077 biotin--[biotin carboxyl-carrier protein] ligase activity
Knockout
CRISPR knockout of HLCS or other ligase genes can create cell models to study the consequences of loss of biotinylation. Such models are valuable for understanding metabolic rewiring and for drug screening. Knockout of ACC1 in cancer cells reduces fatty acid synthesis and inhibits proliferation.
Point Mutation
Introducing patient-specific point mutations into HLCS or target carboxylases using CRISPR base editing or homology-directed repair allows researchers to dissect the functional impact of individual variants. This approach is particularly useful for rare metabolic disorders.
Knock-in
Knock-in of epitope tags (e.g., FLAG, HA) or proximity-labeling enzymes (e.g., AirID) into endogenous loci enables tracking of protein localization and interactors under native regulation. This is powerful for studying the dynamic regulation of biotinylation.
Overexpression
Overexpression of biotin ligases or their target carboxylases can be achieved by CRISPR activation or by lentiviral delivery. This is useful for studying gain-of-function effects in metabolic pathways and for producing biotinylated proteins for structural studies.
How EDITGENE Supports biotin--[biotin carboxyl-carrier protein] ligase activity Research
Researchers studying biotin--[biotin carboxyl-carrier protein] ligase activity-related genes often need to determine whether a candidate gene is causally involved in metabolic regulation, disease, or cellular signaling. EDITGENE provides a comprehensive suite of CRISPR-based services to create precisely engineered cell models, enabling rigorous functional validation of genes associated with GO:0004077.
Contact EDITGENE today to design your custom CRISPR model for biotin--[biotin carboxyl-carrier protein] ligase activity research.
Frequently Asked Questions About biotin--[biotin carboxyl-carrier protein] ligase activity
What is biotin--[biotin carboxyl-carrier protein] ligase activity?
It is an enzymatic activity (GO:0004077) that attaches biotin to a specific lysine on a biotin carboxyl-carrier protein, using ATP and releasing AMP and diphosphate.
What genes are involved in biotin--[biotin carboxyl-carrier protein] ligase activity?
Key genes include HLCS (human holocarboxylase synthetase), bacterial birA, and target genes like ACACA, ACACB, and PC.
What diseases are associated with defects in this activity?
Mutations in HLCS cause multiple carboxylase deficiency, a severe metabolic disorder. Other biotin-dependent carboxylase defects lead to organic acidemias.
How is biotin--[biotin carboxyl-carrier protein] ligase activity regulated?
It is regulated by biotin availability, feedback inhibition by biotinyl-5'-AMP in bacteria, and transcriptional control.
What is the reaction catalyzed by GO:0004077?
ATP + biotin + L-lysyl-[protein] = AMP + diphosphate + H+ + N(6)-biotinyl-L-lysyl-[protein].
What is the role of ATP in this ligase activity?
ATP is used to activate biotin to biotinyl-5'-AMP, which then transfers biotin to the target protein.
How can I study biotin--[biotin carboxyl-carrier protein] ligase activity in the lab?
Common methods include Western blot with streptavidin-HRP, proximity labeling with AirID, and metabolic flux analysis.
What are the synonyms for GO:0004077?
Synonyms include biotin holoenzyme synthetase activity, biotin--protein ligase activity, and holocarboxylase synthetase (HCS).
Is biotin--[biotin carboxyl-carrier protein] ligase activity conserved across species?
Yes, the ATP-grasp fold and mechanism are highly conserved from bacteria to humans.
Can CRISPR be used to study this activity?
Yes, CRISPR knockout, point mutation, and knock-in models are powerful tools to dissect the function of ligases and their targets.
Conclusion
GO:0004077, biotin--[biotin carboxyl-carrier protein] ligase activity, is a central enzymatic function that governs the activation of biotin-dependent carboxylases, impacting fatty acid synthesis, gluconeogenesis, and amino acid catabolism. Its mechanism, conserved across life, involves ATP-dependent activation of biotin and covalent attachment to a specific lysine on target proteins. Defects in this activity cause severe metabolic disorders, and engineered versions of these ligases have become invaluable tools for proximity labeling and interactome mapping. Researchers can leverage CRISPR-based models to precisely manipulate genes involved in this pathway, enabling causal insights into metabolism and disease. EDITGENE offers a full spectrum of services, from knockout and knock-in cell lines to library screening and bioinformatics, to support discovery in this field.
References
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